# Luminous Landscape Forum

## Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: gagemanning on July 04, 2015, 11:41:37 am

Title: Best ISO for IQ280
Post by: gagemanning on July 04, 2015, 11:41:37 am
I was just wondering what base ISO most use for there IQ280 (even the IQ260).  I've always been use to shooting at ISO 100 but I now the IQ280 goes to ISO 35.  Do you lose any dynamic range when you get that low (I know with the Leica systems you can if you shoot below there "normal" ISO).

gage
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 04, 2015, 11:55:28 am
For IQ280, if you shoot at the same aperture and shutter speed, then ISO 35 gives you identical exposure and image quality as ISO 100. ISO 35 is just an extended ISO affecting the calculations of metering forcing you to do ETTR. It is more about marketing. Nikon D810 can shoot at ISO 32.
Title: Best ISO for IQ280
Post by: gagemanning on July 04, 2015, 08:52:17 pm
Thanks voidshatter!

Sent from my iPad using Tapatalk
Title: Re: Best ISO for IQ280
Post by: sbernthal on July 05, 2015, 02:52:47 pm
ISO 35 is not identical to ISO 100 and it's not just marketing.

ISO 35 when underexposed is pushed much better than ISO 100 with the same underexposure.
When pushing overexposure, ISO 100 is better.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 05, 2015, 03:10:31 pm
ISO 35 is not identical to ISO 100 and it's not just marketing.

ISO 35 when underexposed is pushed much better than ISO 100 with the same underexposure.
When pushing overexposure, ISO 100 is better.
Then please supply evidence by means of raw files. Shoot at ISO 35 and ISO 100 for the same aperture and shutter speed.
Title: Re: Best ISO for IQ280
Post by: sbernthal on July 05, 2015, 03:27:33 pm
I don't need to shoot it, because I already have.
I would never have made such a bold statement without testing it myself first.
I did this test when I got my camera, but that was a few years ago, and when I saw your statement today I though maybe I don't remember correctly, so I did it again.
These are Credo files, but it's the same as IQ.

Title: Re: Best ISO for IQ280
Post by: Don Libby on July 05, 2015, 04:11:08 pm
I have a 180.  That said while shooting landscape I always try and shoot using the lowest ISO I can which normally 35.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 05, 2015, 09:20:53 pm
I don't need to shoot it, because I already have.
I would never have made such a bold statement without testing it myself first.
I did this test when I got my camera, but that was a few years ago, and when I saw your statement today I though maybe I don't remember correctly, so I did it again.
These are Credo files, but it's the same as IQ.

http://www.shlomi.net/ftp/T35404.IIQ
http://www.shlomi.net/ftp/T35410.IIQ

Your RAW files don't add up the math. For the same aperture and shutter speed, if the manufacturer's ISO settings were to be trusted, then ISO 100 is supposed to be 1.5EV brighter than ISO 35, but in your RAW files ISO 100 is 1.5EV darker than ISO 35. Clearly something is wrong there:

a) Credo 80 is cheating - they have reversed the ISO settings between 35 and 100;
b) There's a firmware bug;
c) Someone has manipulated the metadata using a hex editor.

Title: Re: Best ISO for IQ280
Post by: sbernthal on July 06, 2015, 12:38:02 am
It's not the same amount of light.
You adapt the lighting so that the histograms of the unpushed files are equal, and then you push them the same amount.
They have identical brightness unpushed and pushed, but not the same noise and detail pushed.

You don't own a Credo/IQ?
Then why did you offer advice to the OP?
Analyzing other people's files doesn't give you the same amount and quality of information as performing tests on your own.
There are plenty of owners here and I believe this is the advice he was soliciting.
Title: Re: Best ISO for IQ280
Post by: Wayne Fox on July 06, 2015, 01:08:37 am
Native ISO of the IQ180/280 is 35.  Any other setting is simply a metadata change ( the camera is basically ISO less). Here is a sample from a couple of years ago when this was discussed extensively over at getDPI.com.

So why use higher ISO’s?  It makes the workflow easier.  If you can’t get the desired exposure at 35, rather than shooting an image that looks extremely underexposed, using 100 will get you to an acceptable starting point.

The higher the ISO the more grain, because  you are underexposing.

(http://www.getdpi.com/gallery/files/4/2/2/8/snapshot-6_4_13-12_05-pm.jpg)
(http://www.getdpi.com/gallery/files/4/2/2/8/snapshot-6_4_13-12_08-pm.jpg)
(http://www.getdpi.com/gallery/files/4/2/2/8/snapshot-6_4_13-1_14-pm.jpg)

(I’ll try to get the full size originals to replace these, but both shots were exposed 1 sec at f/11.  the left shot the back was set to ISO 35, the right it was set to ISO 200. simply making an exposure adjustment in Capture One yielded the corrected ISO 35 image.
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 06, 2015, 01:10:20 am
Hi,

I would have expected the same exposure. If exposure is increased, the noise will be less. What I guess "Voidshatter" means is that if you have same exposure, that is combination of light, aperture and exposure time, identical results would be gained at different ISO settings.

When you talk about the histogram, which one do you mean? Histogram on the back or histogram in Capture One?

Best regards
Erik

It's not the same amount of light.
You adapt the lighting so that the histograms of the unpushed files are equal, and then you push them the same amount.
They have identical brightness unpushed and pushed, but not the same noise and detail pushed.

You don't own a Credo/IQ?
Then why did you offer advice to the OP?
Analyzing other people's files doesn't give you the same amount and quality of information as performing tests on your own.
There are plenty of owners here and I believe this is the advice he was soliciting.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 06, 2015, 01:11:49 am
It's not the same amount of light.
You adapt the lighting so that the histograms of the unpushed files are equal, and then you push them the same amount.
They have identical brightness unpushed and pushed, but not the same noise and detail pushed.

You don't own a Credo/IQ?
Then why did you offer advice to the OP?
Analyzing other people's files doesn't give you the same amount and quality of information as performing tests on your own.
There are plenty of owners here and I believe this is the advice he was soliciting.

You are not testing it correctly. You need to apply the same lightning. If you really want to learn then you should disable flash to simplify things. Credo or IQ isn't that expensive. There are so many superstitions that people just won't admit.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 06, 2015, 01:14:03 am
Native ISO of the IQ180/280 is 35.  Any other setting is simply a metadata change ( the camera is basically ISO less). Here is a simple from a couple of years ago when this was discussed extensively over at getDPI.com.

So why use higher ISO’s?  It makes the workflow easier.  If you can’t get the desired exposure at 35, rather than shooting an image that looks extremely underexposed, using 100 will get you to an acceptable starting point.

The higher the ISO the more grain, because  you are underexposing.(http://)

(http://www.getdpi.com/gallery/files/4/2/2/8/snapshot-6_4_13-12_05-pm.jpg)
(http://www.getdpi.com/gallery/files/4/2/2/8/snapshot-6_4_13-12_08-pm.jpg)
(http://www.getdpi.com/gallery/files/4/2/2/8/snapshot-6_4_13-1_14-pm.jpg)

(I’ll try to get the full size originals to replace these, but both shots were exposed 1 sec at f/11.  the left shot the back was set to ISO 35, the right it was set to ISO 200. Smiley making an exposure adjustment in Capture One yielded the corrected ISO 35 image.

Hi, please compare ISO 35 against ISO 100 for the same aperture and shutter speed by means of RAW files for download. ISO 35 and ISO 100 are the same, but ISO 100 is better than ISO 200.
Title: Re: Best ISO for IQ280
Post by: sbernthal on July 06, 2015, 01:17:09 am
You want to compare ISO 35 and ISO 100 with the same amount of light?
That makes no sense.
The 35 will be darker.
To get similar results you will need to push the 35 and not push the 100 - so what are you comparing?
Of course 100 unpushed will be cleaner than 35 pushed.
Pushing before encoding will be cleaner than pushing after encoding.

For me the question was should I be using ISO 35 or ISO 100 for studio, and then adapt the lights for good exposure.
With ISO 35 the lights need to work harder. Not every light can do it.
Is there a reason to do it?
I think there is.

If you are outside then you use the lowest ISO the light allows you with the parameters you need.
I would not compromise my parameters just to get to ISO 35, of course ISO 100 is good enough in Credo/IQ (not in all Aptus models).
I would use ISO 35 only when there is no sacrifice in the parameters, and the only sacrifice is the longevity and cost of my light.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 06, 2015, 01:22:46 am
You want to compare ISO 35 and ISO 100 with the same amount of light?
That makes no sense.
The 35 will be darker.

In such case, ISO 35 will only appear darker in Capture One or ACR or similar software. You will see that they are identical in RawDigger. If you push the ISO 35 image by 1.5EV in Capture One or ACR then you get exactly the same brightness (and same quality) as of the ISO 100 image.

To get similar results you will need to push the 35 and not push the 100 - so what are you comparing?
Of course 100 unpushed will be cleaner than 35 pushed.
Pushing before encoding will be cleaner than pushing after encoding.

For me the question was should I be using ISO 35 or ISO 100 for studio, and then adapt the lights for good exposure.
With ISO 35 the lights need to work harder. Not every light can do it.
Is there a reason to do it?
I think there is.

If you are outside then you use the lowest ISO the light allows you with the parameters you need.
I would not compromise my parameters just to get to ISO 35, of course ISO 100 is good enough in Credo/IQ (not in all Aptus models).
I would use ISO 35 only when there is no sacrifice in the parameters, and the only sacrifice is the longevity and cost of my light.

As I said in my first reply to this thread, ISO 35 is just a means to affect the metering and force ETTR. If you measure the light and set the parameters with ISO 35 (and fix the lighting), then before you press the shutter, if you now set ISO to 100, then in the final image you would have got the same quality RAW file (same shadow SNR and same highlight) as if you shot with ISO 35. There is no benefit of using ISO 35 other than forcing you ETTR.
Title: Re: Best ISO for IQ280
Post by: sbernthal on July 06, 2015, 01:24:03 am
I would have expected the same exposure. If exposure is increased, the noise will be less.

ISO 35 is for studio.
When you are using ISO 35 in studio, you need to use much more light to get to the same result.
The question is: is there any point to make the effort of extra light just to be using ISO 35, or should I be using ISO 100 and shock my subjects less.

Another pertinent comparison would be long exposures.
I believe ISO 35 would be less noisy, but I haven't tried it as it's not relevant for what I do.

Title: Re: Best ISO for IQ280
Post by: voidshatter on July 06, 2015, 01:28:18 am
ISO 35 is for studio.
When you are using ISO 35 in studio, you need to use much more light to get to the same result.
The question is: is there any point to make the effort of extra light just to be using ISO 35, or should I be using ISO 100 and shock my subjects less.

Another pertinent comparison would be long exposures.
I believe ISO 35 would be less noisy, but I haven't tried it as it's not relevant for what I do.

Then ISO 35 is just forcing you to give more light. If you give the same amount of light for ISO 100 (and same aperture + same shutter speed) you still get the same image. This is also true for ISO 32 on the Nikon D810. It's just extended ISO. Phase One does not explicitly label it in the specifications. This is just marketing.
Title: Re: Best ISO for IQ280
Post by: sbernthal on July 06, 2015, 01:31:11 am
It forces you to give more light, and then you get a file that is DIFFERENT! That's the point.

Title: Re: Best ISO for IQ280
Post by: voidshatter on July 06, 2015, 01:33:18 am
It forces you to give more light, and then you get a file that is DIFFERENT! That's the point.

You can always ignore the ISO 35 setting and deliberately give more light for ISO 100. ISO 35 will not give you better image quality. Without ISO 35 you can still achieve as good image quality if you shoot at ISO 100 and give the same light.

For your use case in the studio, the ISO 35 setting is merely a "+1.5EV exposure compensation for flash" for people like you who have no clue about what is called native ISO. You can dial +1.5EV exposure compensation for your flash and use ISO 100 without relying on ISO 35.

Common superstitions for MFDB:

a) ISO 35 is great;
b) Fullframe CCD has great dynamic range and latitude;
c) 16-bit is awesome.

None of these three is true. It cost me a fortune to realize these.
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 06, 2015, 01:56:50 am
Hi,

- I would say that base ISO seems to be around 35 for the 80 MP backs.

- I don't know if full frame CCD has great dynamic range, that may depend on definition of both great and dynamic range. What I may see is that MFD systems tend to underexpose and thereby protect highlights. For instance, the default film curve in Capture One makes image very bright.

- Readout noise is higher on CCD, so the darks are noisy.

- Yes 16 bit is indeed awesome, but so is 14 bits and even 12 bits.

For the kind of work I am doing my P45+ is mostly quite OK, there are exceptions, however.

Best regards
Erik

You can always ignore the ISO 35 setting and deliberately give more light for ISO 100. ISO 35 will not give you better image quality. Without ISO 35 you can still achieve as good image quality if you shoot at ISO 100 and give the same light.

For your use case in the studio, the ISO 35 setting is merely a "+1.5EV exposure compensation for flash" for people like you who have no clue about what is called native ISO. You can dial +1.5EV exposure compensation for your flash and use ISO 100 without relying on ISO 35.

Common superstitions for MFDB:

a) ISO 35 is great;
b) Fullframe CCD has great dynamic range and latitude;
c) 16-bit is awesome.

None of these three is true. It cost me a fortune to realize these.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 06, 2015, 02:04:25 am
Hi,

- I would say that base ISO seems to be around 35 for the 80 MP backs.

- I don't know if full frame CCD has great dynamic range, that may depend on definition of both great and dynamic range. What I may see is that MFD systems tend to underexpose and thereby protect highlights. For instance, the default film curve in Capture One makes image very bright.

- Readout noise is higher on CCD, so the darks are noisy.

- Yes 16 bit is indeed awesome, but so is 14 bits and even 12 bits.

For the kind of work I am doing my P45+ is mostly quite OK, there are exceptions, however.

Best regards
Erik

Hi, base ISO for 80MP Dalsa is 100. More info here (http://www.getdpi.com/forum/medium-format-systems-and-digital-backs/53676-should-i-not-4.html#post628298).

If you compare the dynamic range of any CCD (regardless of format size) against a 3-year old Nikon D800E you would get disappointed by the CCD. More info here (http://www.getdpi.com/forum/medium-format-systems-and-digital-backs/53676-should-i-not-3.html#post627998) and here (http://www.getdpi.com/forum/medium-format-systems-and-digital-backs/52844-backlight-landscape-photography-realized-say-no-silhouette.html).

Given the inferior dynamic range of all CCDs (more info here (http://www.sensorgen.info/) and here (http://www.dxomark.com/)), there isn't much point to have 16-bit filled with noise in the lower bits. You get better room for post-processing with a 14-bit file from a modern Sony CMOS sensor (e.g. Pentax 645Z or Nikon D810).
Title: Re: Best ISO for IQ280
Post by: sbernthal on July 06, 2015, 02:09:26 am
for people like you who have no clue about what is called native ISO. You can dial +1.5EV exposure compensation for your flash and use ISO 100 without relying on ISO 35.

So if we're getting personal, I will offer these comments:

1. Do you own a Credo/IQ digital back? (no)
2. Do you own a studio? (no)

I would also add this: if you say "dial +1.5EV exposure compensation for your flash", this tells me what you think a flash is.
From your "superstitions" you clearly don't understand why digital backs exist and what they CAN do.
I would agree that for you buying a digital back was a mistake.
Of course, in your mind, all the tens of thousands of digital back buyers are suckers, and you are the one who sees the truth for what it really is.

And over all else - why would you offer advice on hardware you don't own, when so many others own it?
I will give you that you have a lot of appreciation for yourself and your ideas.

Title: Re: Best ISO for IQ280
Post by: voidshatter on July 06, 2015, 02:12:03 am
So if we're getting personal, I will offer these comments:

1. Do you own a Credo/IQ digital back? (no)
2. Do you own a studio? (no)

I would also add this: if you say "dial +1.5EV exposure compensation for your flash", this tells me what you think a flash is.
From your "superstitions" you clearly don't understand why digital backs exist and what they CAN do.
I would agree that for you buying a digital back was a mistake.
Of course, in your mind, all the tens of thousands of digital back buyers are suckers, and you are the one who sees the truth for what it really is.

And over all else - why would you offer advice on hardware you don't own, when so many others own it?
I will give you that you have a lot of appreciation for yourself and your ideas.

I don't know where your confidence is from but it is kinda funny that a Credo user can judge my gear.  ::)
Title: Re: Best ISO for IQ280
Post by: Wayne Fox on July 06, 2015, 02:19:24 am
Hi, base ISO for 80MP Dalsa is 100. More info here (http://www.getdpi.com/forum/medium-format-systems-and-digital-backs/53676-should-i-not-4.html#post628298).
Not sure where in that page you are getting this (long thread, no time), but DxO mark clearly shows the maximum dynamic range of the back is achieved at ISO 35, which is also what Phase stated was the base/native ISO of the back when it was introduced (https://luminous-landscape.com/more-than-megapixels-iq180/).

So using ISO 35 on the IQ back yields it’s greatest dynamic range. ISO 35 is not a “false” ISO setting like using ISO 50 on most dSLR’s which have CMOS sensors that achieve their best dynamic range at around 100 ISO.  If you move to IS0 100 on the IQ180/280, you lose about 2 stops of potential dynamic range.  You can check the chart at DxO to confirm this.  This is the anchor around the back, and why the IQ250 is offering so much better results with high dynamic range imagery. (and why many of us long for a full frame 80-100mp CMOS back designed well enough to perform with tech camera lenses).

To the OP, in a studio situation using ISO 100 may work just fine, because you may have enough control that 8 or 9 stops of dynamic range is all you need (and I think DxO still rates it at almost 12 stops at that ISO although I think the ratings are a stop or so abetter than I’m comfortable with). If you move to ISO 35 it forces you to add light, which is what the sensor is wanting.( No point in “ETTR’ to make up for this, that would basically be identical to moving to ISO 35 and adjusting the lights).  But bottom line if you set the camera to ISO 100, you are basically underexposing the ideal amount of light for the sensor by about 1.3 stops, which isn’t bad, all camera ISO settings trade more sensitivity for less dynamic range. CCD backs just do it a little differently than CMOS backs.
Title: Re: Best ISO for IQ280
Post by: sbernthal on July 06, 2015, 02:24:39 am
That's exactly what I was trying to say.
Maybe you explained it better.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 06, 2015, 02:37:50 am
Not sure where in that page you are getting this (long thread, no time), but DxO mark clearly shows the maximum dynamic range of the back is achieved at ISO 35, which is also what Phase stated was the base/native ISO of the back when it was introduced (https://luminous-landscape.com/more-than-megapixels-iq180/).

So using ISO 35 on the IQ back yields it’s greatest dynamic range. ISO 35 is not a “false” ISO setting like using ISO 50 on most dSLR’s which have CMOS sensors that achieve their best dynamic range at around 100 ISO.  If you move to IS0 100 on the IQ180/280, you lose about 2 stops of potential dynamic range.  You can check the chart at DxO to confirm this.  This is the anchor around the back, and why the IQ250 is offering so much better results with high dynamic range imagery. (and why many of us long for a full frame 80-100mp CMOS back designed well enough to perform with tech camera lenses).

To the OP, in a studio situation using ISO 100 may work just fine, because you may have enough control that 8 or 9 stops of dynamic range is all you need (and I think DxO still rates it at almost 12 stops at that ISO although I think the ratings are a stop or so abetter than I’m comfortable with). If you move to ISO 35 it forces you to add light, which is what the sensor is wanting.( No point in “ETTR’ to make up for this, that would basically be identical to moving to ISO 35 and adjusting the lights).  But bottom line if you set the camera to ISO 100, you are basically underexposing the ideal amount of light for the sensor by about 1.3 stops, which isn’t bad, all camera ISO settings trade more sensitivity for less dynamic range. CCD backs just do it a little differently than CMOS backs.

DxOMark only measures ISO 100 for the IQ180. They didn't even bother putting the data collected for ISO 35 because they knew that ISO 35 is identical as ISO 100. Neither did sensorgen.info because they also know that ISO 35 is just extended ISO offering you no benefit other than forcing you do ETTR of +1.5EV exposure compensation.

You gain the same dynamic range between ISO 35 and ISO 100 (they both give you the best dynamic range out of the IQ180). Anything above ISO 100 would cause the IQ180 lose dynamic range.
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 06, 2015, 04:46:38 am
Hi,

I vould rather say that DxO-mark measures base ISO to be 29 when the baxck is set to ISO 35. So at ISO 35 the camera is exposing very close to nominal ISO. AFAIK as I recall at 100 ISO the back will underexpose 1.5 stops or so. That may give a margin of 1.5EV in the highlights, unless thrown away in the generated raw file.

So, I would say best ISO is 35.

As a side aspect, the two factors involved are quantum efficiency (QE)  and full well capacity (FWC). Low QE leads to low base ISO, as it takes many photons to fill the well, due to low QE. On the other hand large FWC also leads to low base ISO.

The impression I have is that the new Sony sensors have quite large FWC compared to pixel size, so their base ISO is also quite low.

Best regards
Erik

DxOMark only measures ISO 100 for the IQ180. They didn't even bother putting the data collected for ISO 35 because they knew that ISO 35 is identical as ISO 100. Neither did sensorgen.info because they also know that ISO 35 is just extended ISO offering you no benefit other than forcing you do ETTR of +1.5EV exposure compensation.

You gain the same dynamic range between ISO 35 and ISO 100 (they both give you the best dynamic range out of the IQ180). Anything above ISO 100 would cause the IQ180 lose dynamic range.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 06, 2015, 05:08:07 am
Hi,

I vould rather say that DxO-mark measures base ISO to be 29 when the baxck is set to ISO 35. So at ISO 35 the camera is exposing very close to nominal ISO. AFAIK as I recall at 100 ISO the back will underexpose 1.5 stops or so. That may give a margin of 1.5EV in the highlights, unless thrown away in the generated raw file.

So, I would say best ISO is 35.

As a side aspect, the two factors involved are quantum efficiency (QE)  and full well capacity (FWC). Low QE leads to low base ISO, as it takes many photons to fill the well, due to low QE. On the other hand large FWC also leads to low base ISO.

The impression I have is that the new Sony sensors have quite large FWC compared to pixel size, so their base ISO is also quite low.

Best regards
Erik

Hi,

Dxo also measures ISO 29 when the IQ180 is shooting at ISO 100. There is no difference between 35 and 100. The IQ180 is essentially not up to the standard when advertising ISO. It's Phase One's clever way to wrap up for marketing purposes to make users feel good. (You buy something that doesn't perform to meet ISO standard but you are fooled by the extended ISO trick.)
Title: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: BJL on July 06, 2015, 05:48:40 am
Dxo also measures ISO 29 when the IQ180 is shooting at ISO 100. There is no difference between 35 and 100.
Which means that the base ISO speed (the highlight saturation-based _minimum_ recommended exposure index according to the relevant ISO standard ISO12232 (https://en.wikipedia.org/wiki/Film_speed#The_ISO_12232:2006_standard), where it is called SSat) is 29, and there is no difference in the in-camera amplification between the 35 and 100 settings for Exposure Index.

This if anything means that the ISO Exposure Index setting of 35 is closest to the saturation-based measurement SSat that DXO measures (and annoyingly insists on suggesting is the one and only true "ISO" speed measurement, in flat contradiction to what the ISO standard itself says!).  I do not see that EI=35 setting as a marketing trick, but it does mean than when working at that setting and exposing "on-meter", you might have to be more careful about not blowing highlights, because there are only about three stops between metered average light levels and blown highlights, and this is the bare minimum headroom suggested by the ISO standard, not an ideal as some people seem to believe.

P. S. That Ssat [= "ISO" as measured and reported by DXO] is roughly speaking the exposure index such that if metering on a subject of 18% reflectivity, a part of the scene of 100% reflectivity and the same illumination would come in one stop below saturation.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 05:59:47 am
Which means that the base ISO speed (the highlight saturation-based _minimum_ recommended exposure index according to the relevant ISO standard ISO12232 (https://en.wikipedia.org/wiki/Film_speed#The_ISO_12232:2006_standard), where it is called SSat) is 29, and there is no difference in the in-camera amplification between the 35 and 100 settings for Exposure Index.

This if anything means that the ISO Exposure Index setting of 35 is closest to the saturation-based measurement SSat that DXO measures (and annoyingly insists on suggesting is the one and only true "ISO" speed measurement, in flat contradiction to what the ISO standard itself says!).  I do not see that EI=35 setting as a marketing trick, but it does mean than when working at that setting and exposing "on-meter", you might have to be more careful about not blowing highlights, because there are only about three stops between metered average light levels and blown highlights, and this is the bare minimum headroom suggested by the ISO standard, not an ideal as some people seem to believe.

It is indeed a trick to hide the fact that the low light performance is very poor. If Phase One is honest to have the manufacturer's ISO match the measured ISO (so that the plot is close to the nominal line) then everyone will be able to see that noise is catastrophic for anything above ISO 200 (instead of what people now see for ISO 800, severely not up to the ISO standard).
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: JoeKitchen on July 06, 2015, 08:04:32 am
It is indeed a trick to hide the fact that the low light performance is very poor. If Phase One is honest to have the manufacturer's ISO match the measured ISO (so that the plot is close to the nominal line) then everyone will be able to see that noise is catastrophic for anything above ISO 200 (instead of what people now see for ISO 800, severely not up to the ISO standard).

Really?  You just needed to work another bashing of Phase One into this conversation.

And by the way, why anyone would under expose there image at base ISO to only push it in post to match an ISO 100 image is beyond me.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: sbernthal on July 06, 2015, 08:08:27 am
why anyone would under expose there image at base ISO to only push it in post to match an ISO 100 image is beyond me.
My point about pushing is not that you would do that intentionally, but yhat just in case you might need to push once you are in post, the ISO 35 has more data.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 08:32:34 am
My point about pushing is not that you would do that intentionally, but yhat just in case you might need to push once you are in post, the ISO 35 has more data.

I agree that shadow recoverability is important, however given the same aperture, the same shutter speed and the same light, ISO 35 has no more data than ISO 100, because ISO 35 is just extended ISO, and ISO 100 is a base native ISO that is far away from the ISO standard. ISO 200 however, will be worse than ISO 100.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: ErikKaffehr on July 06, 2015, 09:01:53 am
I would say that base ISO as measured by DxO is 29 ISO, pretty close to 35, BTW.

Best regards
Erik

I agree that shadow recoverability is important, however given the same aperture, the same shutter speed and the same light, ISO 35 has no more data than ISO 100, because ISO 35 is just extended ISO, and ISO 100 is a base native ISO that is far away from the ISO standard. ISO 200 however, will be worse than ISO 100.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: JoeKitchen on July 06, 2015, 09:05:07 am
My point about pushing is not that you would do that intentionally, but yhat just in case you might need to push once you are in post, the ISO 35 has more data.

I agree with what you had to say.

In my mind, capturing a perfect exposure at ISO 100, and then reducing the ISO to 35 without changing the light or exposure to capture another image, only to push that ISO 35 exposure in post to match the ISO 100 and compare, makes no sense.

No one would actually shoot like that.  They would pick the ISO settings that suit their needs, given the perimeters and subject, and exposure correctly.

So the test is kind of pointless for photographers who are concentrating on image making, not camera testing.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: BJL on July 06, 2015, 09:32:22 am
It is indeed a trick to hide the fact that the low light performance is very poor.
I guess you mean that the old minimum exposure index setting of 100 was a trick, whereas the new minimum of 35 is more informative.

However, I note that base ISO speed has little to do with low light performance; it measures only highlight handing ability before saturation, not noise levels.  For example, if one sensor has a larger well capacity than another but the same quantum efficiency, dark noise, read noise etc. it will have a lower base ISO speed SSat but the same low light sensitivity and noise characteristics, as measured for example by the rarely used ISO noise-based standards "S40" and "S10": see Wikipedia on ISO noise-based speed measures (https://en.wikipedia.org/wiki/Film_speed#Noise-based_speed)  (I link to Wikipedia because ISO charges for access to its standards documents, but CIPA might give free access to related information.)

One has to be aware that the base ISO or SSat has little connection to the ISO measure of film speed -- if anything, ISO film speed is closer to those ISO SNR based measures.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: sbernthal on July 06, 2015, 09:40:04 am
I agree with what you had to say.

In my mind, capturing a perfect exposure at ISO 100, and then reducing the ISO to 35 without changing the light or exposure to capture another image, only to push that ISO 35 exposure in post to match the ISO 100 and compare, makes no sense.

No one would actually shoot like that.  They would pick the ISO settings that suit their needs, given the perimeters and subject, and exposure correctly.

So the test is kind of pointless for photographers who are concentrating on image making, not camera testing.

I am not able to follow his logic and he is not able to follow mine.
He is insisting on the "same light different ISO" test, which makes no sense to me.
It must be my Credo ownership that limits my intellect.
As he said - I have "no clue about what is called native ISO" - must be my 20 years as computer engineer followed by my 10 years as a professional photographer that hinder my technical understanding abilities.

ISO 35 has more information for pushing shadows - that is the main thing I need to know when deciding on my ISO, since I can make the light to whatever I want.
Note that by my tests, it is not correct that in general ISO 35 has more dynamic range - for recovering highlights it is worse than ISO 100.
Both make perfect sense, if you consider the number of photons hitting the sensor for each ISO.
BTW now I remember that when I got my camera I also did a long exposure test and ISO 35 was cleaner.
Title: Re: Best ISO for IQ280
Post by: RobertJ on July 06, 2015, 10:01:07 am
Well this thread turned into a shit storm.  I have learned nothing.
Title: Re: Best ISO for IQ280
Post by: Ken R on July 06, 2015, 10:23:03 am
Hi, base ISO for 80MP Dalsa is 100. More info here (http://www.getdpi.com/forum/medium-format-systems-and-digital-backs/53676-should-i-not-4.html#post628298).

If you compare the dynamic range of any CCD (regardless of format size) against a 3-year old Nikon D800E you would get disappointed by the CCD. More info here (http://www.getdpi.com/forum/medium-format-systems-and-digital-backs/53676-should-i-not-3.html#post627998) and here (http://www.getdpi.com/forum/medium-format-systems-and-digital-backs/52844-backlight-landscape-photography-realized-say-no-silhouette.html).

Given the inferior dynamic range of all CCDs (more info here (http://www.sensorgen.info/) and here (http://www.dxomark.com/)), there isn't much point to have 16-bit filled with noise in the lower bits. You get better room for post-processing with a 14-bit file from a modern Sony CMOS sensor (e.g. Pentax 645Z or Nikon D810).

Man, you do not give up. Gotta give you mad points for being persistent. You will not be happy until "the truth" about PhaseOne is known to all and PhaseOne is gone and buried forever (and maybe you won't be happy until they give some of their profits back to those who bought into the system). You make them sound like they are scammers. That anything but the exmor is junk. Meanwhile amazing photographs and prints are being made with lots of different gear worldwide right now.

Here some real world samples of a snap I mad while scouting a location a while back. I usd a IQ160 on a H1 with 80mm H lens handheld at 1/160 sec f2.8 iso 200. Processed in Lightroom which is not ideal, with just some quick and basic adjustments.

First is the whole frame then a 100% crop.

Looks good enough to me. Iso 200 is very very far from "worhtless" on the newer dalsa ccd sensors.

Could I have gotten the same result by using iso 50 and the same exposure and just increasing exposure in post? Of course, but I did not want to have a dark preview image in the rear lcd of the back.
Title: Re: Best ISO for IQ280
Post by: chrismuc on July 06, 2015, 10:32:23 am
I made a simple test with my IQ180: 3 exposures

- at ISO 35
- at ISO 35 1.5 stops underexposed (= exposed like ISO 100)
- at ISO 100

If I open the files in ACR and add 1,5 stops exposure to the second picture, I see the following:

- the three pictures look very similar, but
- the second and third are more grainy in medium and dark areas

so my conclusion would be that the IQ180 is

- ISO 35 native* (not ISO 100 like Void suggests)
- up to ISO 100 in reality also ISO 35, just underexposed and already compensated by Phase RAW firmware (which means the picture looks correct exposed if opened in ACR or C1, just raw digger and similar raw programs can detect), but has reduced DR compared to shot at ISO 35
- above ISO 100 basically the same like below, means the real sensitivity is 1,5 stops lower than read on the back and internally compensated (which of course reduces the DR)

End of the story: Shoot ISO 35 wherever possible to get the 13.5 steps DXO-DR (acc. my experience up to 8s exposure time, then degration of file quality), then maybe still stay at ISO 35, underexpose and push in RAW conversion .

* I also read the enclosed DXO measurement of ISO sensitivity that way
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 06, 2015, 12:51:57 pm
I made a simple test with my IQ180: 3 exposures

- at ISO 35
- at ISO 35 1.5 stops underexposed (= exposed like ISO 100)
- at ISO 100

If I open the files in ACR and add 1,5 stops exposure to the second picture, I see the following:

- the three pictures look very similar, but
- the second and third are more grainy in medium and dark areas

so my conclusion would be that the IQ180 is

- ISO 35 native* (not ISO 100 like Void suggests)
- up to ISO 100 in reality also ISO 35, just underexposed and already compensated by Phase RAW firmware (which means the picture looks correct exposed if opened in ACR or C1, just raw digger and similar raw programs can detect), but has reduced DR compared to shot at ISO 35
- above ISO 100 basically the same like below, means the real sensitivity is 1,5 stops lower than read on the back and internally compensated (which of course reduces the DR)

End of the story: Shoot ISO 35 wherever possible to get the 13.5 steps DXO-DR (acc. my experience up to 8s exposure time, then degration of file quality), then maybe still stay at ISO 35, underexpose and push in RAW conversion .

* I also read the enclosed DXO measurement of ISO sensitivity that way

Hi, please supply RAW files for same aperture, same shutter speed, same light for ISO 35 and ISO 100.

DXO measured 13.5 stops of DR at ISO 100. If you believe ISO 35 give better DR than ISO 100, then DXO has made a serious mistake underestimating the true performance of the IQ180.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 06, 2015, 12:57:07 pm
Man, you do not give up. Gotta give you mad points for being persistent. You will not be happy until "the truth" about PhaseOne is known to all and PhaseOne is gone and buried forever (and maybe you won't be happy until they give some of their profits back to those who bought into the system). You make them sound like they are scammers. That anything but the exmor is junk. Meanwhile amazing photographs and prints are being made with lots of different gear worldwide right now.

Here some real world samples of a snap I mad while scouting a location a while back. I usd a IQ160 on a H1 with 80mm H lens handheld at 1/160 sec f2.8 iso 200. Processed in Lightroom which is not ideal, with just some quick and basic adjustments.

First is the whole frame then a 100% crop.

Looks good enough to me. Iso 200 is very very far from "worhtless" on the newer dalsa ccd sensors.

Could I have gotten the same result by using iso 50 and the same exposure and just increasing exposure in post? Of course, but I did not want to have a dark preview image in the rear lcd of the back.

Hi, in your IQ160 case you need same condition to compare ISO 50 and ISO 100, that is, same aperture, same shutter speed, same light, same condition. Upload the RAW files and I'll be able to show you ISO 50 is the same as ISO 100, but better than ISO 200.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 01:28:55 pm
I would say that base ISO as measured by DxO is 29 ISO, pretty close to 35, BTW.

Best regards
Erik

Base ISO for Nikon D810 as measured by DxO is ISO 47. It is closer to ISO 32. Do you think Nikon gave false information saying that ISO 32 is extended ISO?
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 01:32:09 pm
I am not able to follow his logic and he is not able to follow mine.
He is insisting on the "same light different ISO" test, which makes no sense to me.
It must be my Credo ownership that limits my intellect.
As he said - I have "no clue about what is called native ISO" - must be my 20 years as computer engineer followed by my 10 years as a professional photographer that hinder my technical understanding abilities.

ISO 35 has more information for pushing shadows - that is the main thing I need to know when deciding on my ISO, since I can make the light to whatever I want.
Note that by my tests, it is not correct that in general ISO 35 has more dynamic range - for recovering highlights it is worse than ISO 100.
Both make perfect sense, if you consider the number of photons hitting the sensor for each ISO.
BTW now I remember that when I got my camera I also did a long exposure test and ISO 35 was cleaner.

Hi, all I said is that you won't get better dynamic range with ISO 35 over ISO 100. If you don't agree, then supply RAW files to disprove me (same aperture, same shutter speed, same flash - you do know what is called comparison under same condition don't you?).
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: JoeKitchen on July 06, 2015, 02:23:51 pm
But why?  Why would anyone shoot like that.  It makes no sense.  Most photographers, when dropping the ISO, would not think twice about using more light.

Some of these tests mean nothing to us who actually concentrate on making images.  I don't care how similar files will look after pushing lower ISOs harder then higher ISOs.  I care about light, and properly exposing the image, so I can assess the light in the image.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 02:29:28 pm
But why?  Why would anyone shoot like that.  It makes no sense.  Most photographers, when dropping the ISO, would not think twice about using more light.

Some of these tests mean nothing to us who actually concentrate on making images.  I don't care how similar files will look after pushing lower ISOs harder then higher ISOs.  I care about light, and properly exposing the image, so I can assess the light in the image.

Then in your logic you would shoot a Nikon D810 at ISO 32. You are saying that most Nikon / Canon users are not using their gear correctly.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: sbernthal on July 06, 2015, 02:34:34 pm
Hi, all I said is that you won't get better dynamic range

You said a couple more things that you shouldn't have.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 02:38:49 pm
You said a couple more things that you shouldn't have.

Look into my original first reply. What do you think is wrong there?  ;)
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: JoeKitchen on July 06, 2015, 02:41:52 pm
Then in your logic you would shoot a Nikon D810 at ISO 32. You are saying that most Nikon / Canon users are not using their gear correctly.

Ahhh ... no!

I said you expose correctly for the ISO you are shooting at, or you pick the ISO that allows you to expose correctly.  If a Nikon user is shooting at ISO 100 and exposing correctly for that ISO, then they are doing it right.

If they decided to shoot at ISO 100, underexposing the image so they get the same results as if they exposed at ISO 200 after pushing in post one stop, then they have workflow issues.  Why?  Because unless you are shooting tethered and have the push automatically applied, it would be impossible to assess your exposure and whether or not you got the exposure correct.  But even so, it still is not the best way to work.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: sbernthal on July 06, 2015, 02:45:53 pm
But why?  Why would anyone shoot like that.  It makes no sense.  Most photographers, when dropping the ISO, would not think twice about using more light.

I think I figured out what he wants.
He's a guy that holds his camera and runs around town.
That explains why a digital back was not very useful for him.

For an available light situation without tripod, there isn't much difference between ISO 100 and 35, and indeed I would shoot 100 unless there was very much light or I wanted to open aperture more than the light allowed. BTW this is an important advantage of the ISO 35 capability, which is again not a marketing trick.

A studio shooter sees light completely differently. You make your own light according to what you need. So for me the question is, assuming a balanced exposure, what ISO is best to start from, taking into account future post. BTW not always 35. If your problem is shadows then 35, if your problem is highlights then 100, even in studio.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: sbernthal on July 06, 2015, 02:50:30 pm
Look into my original first reply. What do you think is wrong there?  ;)

If after all this explaining you still can't figure out why your initial statement is completely erroneous,
and why you shouldn't offer advice based on speculation,
and why it's not cool to call people stupid on internet forums,

the there's not much else I can do for you.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: ErikKaffehr on July 06, 2015, 02:51:59 pm
Hi,

That guy has an IQ-250, which I think he cross graded from an IQ-260. Absolutely positive about the IQ-250, I even got a lot of raw samples from him. I am not sure he is coming from the IQ-260.

He likes very long exposures and finds that the IQ-250 and the Nikons work for him and the CCD backs don't.

Best regards
Erik

I think I figured out what he wants.
He's a guy that holds his camera and runs around town.
That explains why a digital back was not very useful for him.

For an available light situation without tripod, there isn't much difference between ISO 100 and 35, and indeed I would shoot 100 unless there was very much light or I wanted to open aperture more than the light allowed. BTW this is an important advantage of the ISO 35 capability, which is again not a marketing trick.

A studio shooter sees light completely differently. You make your own light according to what you need. So for me the question is, assuming a balanced exposure, what ISO is best to start from, taking into account future post. BTW not always 35. If your problem is shadows then 35, if your problem is highlights then 100, even in studio.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 02:57:31 pm
Ahhh ... no!

I said you expose correctly for the ISO you are shooting at, or you pick the ISO that allows you to expose correctly.  If a Nikon user is shooting at ISO 100 and exposing correctly for that ISO, then they are doing it right.

Your definition of "correct exposure" is vague. If you mean to ETTR to the edge of blown highlight in the RAW file, then you would lose 0.4 stops of dynamic range if you shoot a Nikon D810 at ISO 100 instead of shooting at ISO 64 or ISO 32. If you mean to make the histogram of in-body playback look right then ISO 32 would cause more blown highlight and ISO 100 would give you more noise in shadow.

If they decided to shoot at ISO 100, underexposing the image so they get the same results as if they exposed at ISO 200 after pushing in post one stop, then they have workflow issues.  Why?  Because unless you are shooting tethered and have the push automatically applied, it would be impossible to assess your exposure and whether or not you got the exposure correct.  But even so, it still is not the best way to work.

You are getting it upside down. Shooting an IQ280 at ISO 100 with ETTR would require you to pull down exposure in post-processing, not pushing up exposure in post-processing. It would give you the same result as of ISO 35. If you disagree, then provide evidence by means of RAW files.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 03:01:12 pm
I think I figured out what he wants.
He's a guy that holds his camera and runs around town.
That explains why a digital back was not very useful for him.

No, I don't do any street photography.

For an available light situation without tripod, there isn't much difference between ISO 100 and 35, and indeed I would shoot 100 unless there was very much light or I wanted to open aperture more than the light allowed. BTW this is an important advantage of the ISO 35 capability, which is again not a marketing trick.

There is no advantage of the ISO 35 capability when you know how to shoot at ISO 100 (i.e. with +1.5EV EC for your metering and flash).

A studio shooter sees light completely differently. You make your own light according to what you need. So for me the question is, assuming a balanced exposure, what ISO is best to start from, taking into account future post. BTW not always 35. If your problem is shadows then 35, if your problem is highlights then 100, even in studio.

There is no difference between ISO 35 and ISO 100 if you know how to make reference to blown highlight according to the playback. Just stick to your habit.
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 06, 2015, 03:01:18 pm
Hi,

For the best result, you always try to get as many photons (particles of light) on the sensor as possible. So you want to have maximum exposure, without clipping any highlights. I am pretty sure that using minimum ISO will give the best results. Going up in ISO will reduce exposure. This may in a sense protect highlights.

On the cameras I have I essentially always use minimum ISO and check the histogram carefully. I also use "RawDigger" to check out the real histograms. Histograms in raw processors seldom show correct values. Worst offender may be Lightroom, doing intensive highlight recovery before indicating clipping. C1 has also ideas of it's own.

Best regards
Erik

I was just wondering what base ISO most use for there IQ280 (even the IQ260).  I've always been use to shooting at ISO 100 but I now the IQ280 goes to ISO 35.  Do you lose any dynamic range when you get that low (I know with the Leica systems you can if you shoot below there "normal" ISO).

gage
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 03:04:29 pm
If after all this explaining you still can't figure out why your initial statement is completely erroneous,
and why you shouldn't offer advice based on speculation,
and why it's not cool to call people stupid on internet forums,

the there's not much else I can do for you.

I did not offer advice base on speculation. Instead, I made these conclusions by careful and repeated experiments. You are the one who did not do proper tests before you made your own imagination.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: JoeKitchen on July 06, 2015, 03:05:18 pm
Your definition of "correct exposure" is vague. If you mean to ETTR to the edge of blown highlight in the RAW file, then you would lose 0.4 stops of dynamic range if you shoot a Nikon D810 at ISO 100 instead of shooting at ISO 64 or ISO 32. If you mean to make the histogram of in-body playback look right then ISO 32 would cause more blown highlight and ISO 100 would give you more noise in shadow.

You are getting it upside down. Shooting an IQ280 at ISO 100 with ETTR would require you to pull down exposure in post-processing, not pushing up exposure in post-processing. It would give you the same result as of ISO 35. If you disagree, then provide evidence by means of RAW files.

Man you really have a heard time understanding what is being said here.

My definition of correct exposure is the exposure that makes the image look the way you want it to look.

Photography, for me, or at least when I am being paid good money to create images, first begins with an idea of what I want.  I think it through and by the time I am ready to leave for the location, I already know how I want it to look like.  I know how I am going to compose it, how I will style it, and how I will light it.  I pick an ISO that will allow me to get the image I am thinking about with as little steps as possible and as little tech thinking as possible, which mean picking an ISO that exposes the images correctly, for how I want it to look.

Under or over exposing only to correct that in post is kind of working against yourself.  You are increasing your workflow and decreasing your ability to assess your work on location with a client looking over your shoulder and you having to manage or worrying about a dozen other things.

The test you are describing, when it comes to working like I mentioned above, which many working pros do, means absolutely nothing.

There is no point in it.

Not to mention if you can shoot at ISO 35 and get what you are thinking about, why would you not?  You always get better shadow recovery at lower ISOs.  Of course Sbernthal's observation about highlights and shooting at ISO 100 is very valid too.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 06, 2015, 03:06:51 pm
Hi,

For the best result, you always try to get as many photons (particles of light) on the sensor as possible. So you want to have maximum exposure, without clipping any highlights. I am pretty sure that using minimum ISO will give the best results. Going up in ISO will reduce exposure. This may in a sense protect highlights.

On the cameras I have I essentially always use minimum ISO and check the histogram carefully. I also use "RawDigger" to check out the real histograms. Histograms in raw processors seldom show correct values. Worst offender may be Lightroom, doing intensive highlight recovery before indicating clipping. C1 has also ideas of it's own.

Best regards
Erik

+1 for RawDigger to check the real histogram. In-camera playback is not reliable. Your advice could also apply to Nikon D810 users - you could suggest them to shoot at ISO 32.
Title: Re: Best ISO for IQ280
Post by: sbernthal on July 06, 2015, 03:09:04 pm
For the best result, you always try to get as many photons (particles of light) on the sensor as possible.

If the counter attached to the pixel reaches 100% of what it can count, then you do have too many photons, and then this area has no detail.
More photons is always best, but only if you calibrate the counter (ISO) not to multiply so much it reaches 100%.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 03:16:18 pm
Man you really have a heard time understanding what is being said here.

My definition of correct exposure is the exposure that makes the image look the way you want it to look.

Photography, for me, or at least when I am being paid good money to create images, first begins with an idea of what I want.  I think it through and by the time I am ready to leave for the location, I already know how I want it to look like.  I know how I am going to compose it, how I will style it, and how I will light it.  I pick an ISO that will allow me to get the image I am thinking about with as little steps as possible and as little tech thinking as possible, which mean picking an ISO that exposes the images correctly, for how I want it to look.

Under or over exposing only to correct that in post is kind of working against yourself.  You are increasing your workflow and decreasing your ability to assess your work on location with a client looking over your shoulder and you having to manage or worrying about a dozen other things.

The test you are describing, when it comes to working like I mentioned above, which many working pros do, means absolutely nothing.

There is no point in it.

Not to mention if you can shoot at ISO 35 and get what you are thinking about, why would you not?  You always get better shadow recovery at lower ISOs.  Of course Sbernthal's observation about highlights and shooting at ISO 100 is very valid too.

If you do landscape photography of a high contrast scene for which you cannot bracket, then there is little chance that you could make it "look right" in the in-camera playback. You would need to carefully prevent highlight details being blown out. Without the use of RawDigger it is pretty difficult to accurately tell the actual area of blown highlight. You would have to rely on your own experience with the in-camera playback. Of course ISO 100 would give you a more overexposed look in the playback but you still retain the same amount of information as ISO 35.

(https://1xzpta.dm2302.livefilestore.com/y2pL_9-FdEjygLJRr0Q1rHEw-EAZ_bi1P_coW_aqQSCxn5aWbgqB1F58_9j_jbEKeiCvbCZ05JRYSOHyoS90fei8eyB4Fm_PieB6i3pmi4p10p5AhM8MSF47sgFLxj6pvNqFWnuOlusnpmVkvFXTjbO-Q/8.JPG?psid=1)

(https://1xzpta.dm2302.livefilestore.com/y2pg9gVA7xyAWtde2wlMPD52CbCS01LAOYfwwGIPssKKOykSYbLmzSZ031mvc8BHY1qJjCUDyBJSwKXXYXdCBRGX_LBjV-C_ceMHlPIVDeFYbKyprOsjnMdeH1JEq-xr4vYfq2JYbUjAOw7k24xxe956A/CF000288.jpg?psid=1)
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 06, 2015, 03:17:38 pm
If the counter attached to the pixel reaches 100% of what it can count, then you do have too many photons, and then this area has no detail.
More photons is always best, but only if you calibrate the counter (ISO) not to multiply so much it reaches 100%.

For the same aperture, the same shutter speed and the same light, ISO 100 of IQ280 will not give you more area of blown highlight when compared against ISO 35. ISO 200 however, will cause more area of blown highlight.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 03:21:03 pm
You always get better shadow recovery at lower ISOs.  Of course Sbernthal's observation about highlights and shooting at ISO 100 is very valid too.

I need to see RAW files as hard evidence (for the case of ISO 35 vs ISO 100). Please supply RAW files of the same aperture, the same shutter speed and the same light, for ISO 35 and ISO 100.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: JoeKitchen on July 06, 2015, 03:29:51 pm
I need to see RAW files as hard evidence (for the case of ISO 35 vs ISO 100). Please supply RAW files of the same aperture, the same shutter speed and the same light, for ISO 35 and ISO 100.

No, because I would not shoot like that.  It does not make sense.

I would properly expose the image for the given ISO.  If you properly expose an ISO 35 image and compare it to a properly exposed ISO 100 image, the ISO 35 image gives you better shadows.

Now of course if you under expose an ISO 35 image and push it, it will look very very similar to an properly exposed ISO 100, but there is no reason to shoot like that unless you do not have the proper equipment.

By the way, have you considered graded neutral density filters?  I ask because Joe Cornish shoots images like the one posted, with as much of the image properly exposed as possible through the lens.  His images, at 100%, are very nice.  Nice micro contrast, nice colors.  Sure there are limits to those filters, but I would rather have most of the image properly exposed and only work on areas that got missed, instead of have the majority of the images not properly exposed and work on all of it.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 03:48:18 pm
No, because I would not shoot like that.  It does not make sense.

Then it makes no sense for you to shoot a Nikon D810 at anything above ISO 32 when you can shoot at ISO 32.

I would properly expose the image for the given ISO.  If you properly expose an ISO 35 image and compare it to a properly exposed ISO 100 image, the ISO 35 image gives you better shadows.

Now of course if you under expose an ISO 35 image and push it, it will look very very similar to an properly exposed ISO 100, but there is no reason to shoot like that unless you do not have the proper equipment.

You can shoot at ISO 35 for any "proper exposure" you want. I can shoot at ISO 100 for a brighter look of playback and then pull down exposure in post-processing and still achieve as good image quality as yours. You don't have advantage of image quality over me.

By the way, have you considered graded neutral density filters?  I ask because Joe Cornish shoots images like the one posted, with as much of the image properly exposed as possible through the lens.  His images, at 100%, are very nice.  Nice micro contrast, nice colors.  Sure there are limits to those filters, but I would rather have most of the image properly exposed and only work on areas that got missed, instead of have the majority of the images not properly exposed and work on all of it.

Of course I use ND grad and I don't need a lecture on that. Indeed ND grad is vulnerable to non-straightline skyline scenes. For example, if the sun is lower than a building, then your ND grad will cut the building making the building look dark and you would still need to push the shadow out of the building in post-processing. Indeed ND grad will make any cloud above the sun to be underexposed, relying on the dynamic range of the sensor in post-processing.

Example of a scene where an ND grad would fail: https://500px.com/photo/92579427/
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: JoeKitchen on July 06, 2015, 04:03:30 pm
Then it makes no sense for you to shoot a Nikon D810 at anything above ISO 32 when you can shoot at ISO 32.

You can shoot at ISO 35 for any "proper exposure" you want. I can shoot at ISO 100 for a brighter look of playback and then pull down exposure in post-processing and still achieve as good image quality as yours. You don't have advantage of image quality over me.

Of course I use ND grad and I don't need a lecture on that. Indeed ND grad is vulnerable to non-straightline skyline scenes. For example, if the sun is lower than a building, then your ND grad will cut the building making the building look dark and you would still need to push the shadow out of the building in post-processing. Indeed ND grad will make any cloud above the sun to be underexposed, relying on the dynamic range of the sensor in post-processing.

Example of a scene where an ND grad would fail: https://500px.com/photo/92579427/

1.  Yes, that is how I would work, if that ISO was available on the given camera.

2.  What if we both had proper exposures for the given iso, so the image looked as close as we wanted it to without any post work, but we needed to push the shadows.  Yours would look worse then mine.

3.  Good example, however you are already under-exposing almost all of the image already.  Instead, why not properly expose most of the image and push the top part of the building to match the rest?  Easier work-flow in post?  (I could imagine it would be difficult to match the top of the building to the bottom.)
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 04:21:42 pm
1.  Yes, that is how I would work, if that ISO was available on the given camera.

Then do you think Nikon is silly to advertise ISO 32 as extended ISO for the D810?

2.  What if we both had proper exposures for the given iso, so the image looked as close as we wanted it to without any post work, but we needed to push the shadows.  Yours would look worse then mine.

Your definition of "proper exposure" is based on the playback inside the camera - you think it is proper when you see a good histogram in the playback inside the camera/digital back. My definition of "proper exposure" is to check with RawDigger and verify that I have made ETTR as much as possible without blowing out the highlight details I want - I can shoot at ISO 100 for an overexposed look for the playback. My way will give best image quality out of a single RAW file (regardless of ISO 35 or ISO 100). Your way is not reliable and may waste dynamic range, because the histogram inside the camera/digital back is not reliable, and you may be wasting highlight recoverability.

3.  Good example, however you are already under-exposing almost all of the image already.  Instead, why not properly expose most of the image and push the top part of the building to match the rest?  Easier work-flow in post?  (I could imagine it would be difficult to match the top of the building to the bottom.)

It will not be easy task. This is long exposure and the light condition changes fast during the sunset process. If you shoot most of the frames with blown sky then there is no way to recover that in post-processing for the long exposure look. If you shoot a frame for the building before you start the long exposure process then the color temperature will be higher; if you shoot after then the color temperature will be lower. The light and shadow will also easily look abnormal when you compose two things taken at very different times.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: JoeKitchen on July 06, 2015, 04:42:00 pm
Then do you think Nikon is silly to advertise ISO 32 as extended ISO?

Your definition of "proper exposure" is based on the playback inside the camera - you think it is proper when you see a good histogram in the playback inside the camera/digital back. My definition of "proper exposure" is to check with RawDigger and verify that I have made ETTR as much as possible without blowing out the highlight details I want - I can shoot at ISO 100 for an overexposed look for the playback. My way will give best image quality out of a single RAW file (regardless of ISO 35 or ISO 100). Your way is not reliable and may waste dynamic range, because the histogram inside the camera/digital back is not reliable, and you may be wasting highlight recoverability.

It will not be easy task. This is long exposure and the light condition changes fast during the sunset process. If you shoot a frame for the building before you start the long exposure process then the color temperature will be higher; if you shoot after then the color temperature will be lower. The light and shadow will also easily look abnormal when you compose two things taken at very different times.

1.  Don't know, don't use the camera.  I was not aware that that ISO was offered.

2.  My definition of proper exposure is not based on the play back, but what I feel is the closest look I can get to what I want without any post work.  I almost always shoot tethered, so I do not really on the playback.  With that said, I see what you are saying now.  You are worried about the highlights, whereas I am worried about the shadows, especially with an interior.  Operating at ISO 100 would be better in your situation, the lowest ISO possible is best in my situation.

3.  I meant within a single capture, mask out the under-exposed area of the building and brighten it to match the rest.  Not sure if this would be possible with a building, but with small areas of an almost smooth horizon, it may be plausible.  (I realize layering an image from seconds before or after at that time of day is not always possible.)

And after thinking about it, if I were to use a ND Grad filter to get the sky properly exposed, I would need to worry about shadow details.  So, lower ISO would be best.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 04:51:13 pm
1.  Don't know, don't use the camera.  I was not aware that that ISO was offered.

Then you could advise Nikon and Canon to deliberately hide the fact that ISO 32 or ISO 50 are extended ISO - this makes users feel good, and ISO 32 of Nikon D810 beats ISO 35 of IQ280 in terms of advertised low ISO number as well as dynamic range.

2.  My definition of proper exposure is not based on the play back, but what I feel is the closest look I can get to what I want without any post work.  I almost always shoot tethered, so I do not really on the playback.

If you shoot tethered, try to ETTR as much as possible without blowing out highlight by means of verification with RawDigger instead of Capture One (regardless of ISO 35 or ISO 100), then pulling down the exposure in post-processing, would give you better shadow, when compared against your feel.

3.  I meant within a single capture, mask out the under-exposed area of the building and brighten it to match the rest.  Not sure if this would be possible with a building, but with small areas of an almost smooth horizon, it may be plausible.  (I realize layering an image from seconds before or after at that time of day is not always possible.)

Yes if you shoot an LCC with the ND grad on, then apply LCC correction in Capture One, then apply highlight recover globally on the image, you can essentially achieve the effect you are talking about. However the signal-to-noise ratio on that building will still suffer. This is also true for any cloud above the sun when you use ND grad to cover the sun. Joe Cornish does not deliberately shoot against the sun for long exposure.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 04:52:58 pm
And after thinking about it, if I were to use a ND Grad filter to get the sky properly exposed, I would need to worry about shadow details.

If you use an ND grad to cover the sun, then any cloud above the sun will be underexposed.

So, lower ISO would be best.

Again, I need to see evidence by means of RAW files. ISO 35 indeed is best but not better than ISO 100.
Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 05:21:04 pm
With that said, I see what you are saying now.  You are worried about the highlights, whereas I am worried about the shadows, especially with an interior.  Operating at ISO 100 would be better in your situation, the lowest ISO possible is best in my situation.

No. I'm not saying ISO 100 is better in my situation. I'm saying ISO 100 is as good as ISO 35 when the user knows how to ETTR as much as possible to retain highlight details - this way gives best shadow recoverability. ISO 35 is best, but not better than ISO 100. ISO 100 is also best, but not better or worse than ISO 35.
Title: Re: Best ISO for IQ280
Post by: Paul2660 on July 06, 2015, 05:53:57 pm
This is from the DxO Mark scores, on the IQ180.  They do rate the Phase iso's of 35, 50 and  100 as all at iso 29.

The problem as I see it is that photographers tend to use the same logic for iso increases on CCD and CMOS.  The issue on whether the iso on the Phase One CCD is really an increase? or is it just a metadata setting for C1 to use later on.  Unlike a CMOS iso increase which as I understand it, is an actual increase in gain on the chip.

There have been several comparisons of IQ180 iso 35 and iso 200 shots.  I tried to find the one done a few years ago, but was not able.  But the net, was that the image looked the same between a under exposed iso 35 by 2.5 stops  and a correctly exposed.  The two images when viewed side by side look pretty much the same noise levels etc.  (Note I may have this backwards, i.e. the iso 35 was even exposed but the iso 200 was under exposed)

I have put this question forward several times on various forums but it's never really been answered very clearly.  From reading various posts by users (as I have never found anything written officially by Phase One) is that you really don't change the gain on a CCD by pushing the iso but I am not qualified enough to know the answer.

I my use, (P45+, IQ160, IQ260, and IQ180), I feel that you can "push" the CCD maybe one stop, So on my IQ260, that would be either iso 50 to iso 100 or iso 100 to iso 200 depending on where you feel the real base iso rests.  In normal exposure ranges say 1" to 1/250th most times I will not see much difference between iso 50 or iso 100 on my 260.  What makes the difference to me is say the difference in shutter speeds, say 1/60 vs 1/125 at F11.  Just that one shutter speed difference can make a big difference in the noise in the shadows.  CCD needs light and lots of it and trying to push it on a dim day or late/early morning to me is not a good solution vs taking a longer exposure.

By the time you get to iso 200 on the IQ260 I feel that the shadows show quite a bit of noise and color loss, but areas that have good light can still allow for a very good clean shot, but I know I won't be able to push the shadows at all.  By iso 400, there is loss in color/sat thought the file.  Areas that were brightly exposed might allow for some recovery in post, but the loss in details can't be pulled back.

Of course moving to sensor plus changes all of this un to around iso 800.  But the loss in resolution makes this something I rarely do.

Paul Caldwell

Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: Ken R on July 06, 2015, 06:55:38 pm
Then it makes no sense for you to shoot a Nikon D810 at anything above ISO 32 when you can shoot at ISO 32.

You can shoot at ISO 35 for any "proper exposure" you want. I can shoot at ISO 100 for a brighter look of playback and then pull down exposure in post-processing and still achieve as good image quality as yours. You don't have advantage of image quality over me.

Of course I use ND grad and I don't need a lecture on that. Indeed ND grad is vulnerable to non-straightline skyline scenes. For example, if the sun is lower than a building, then your ND grad will cut the building making the building look dark and you would still need to push the shadow out of the building in post-processing. Indeed ND grad will make any cloud above the sun to be underexposed, relying on the dynamic range of the sensor in post-processing.

Example of a scene where an ND grad would fail: https://500px.com/photo/92579427/

Nice image but looks a bit odd, too high unnatural dynamic range boosted shadows and it is easy to see an abrupt transition from sky to building (see crop attached). Kinda looks like an outline / halo. I mean it's your style and looks good but it is not the only style of photography.

Title: Re: Best ISO for IQ280: base ISO speed (_minimum_ safe EI) is 29, it seems
Post by: voidshatter on July 06, 2015, 07:09:30 pm
Nice image but looks a bit odd, too high unnatural dynamic range boosted shadows and it is easy to see an abrupt transition from sky to building (see crop attached). Kinda looks like an outline / halo. I mean it's your style and looks good but it is not the only style of photography.

Please don't make it personal. I never said shooting backlit long exposure is the only style of photography. I only said such style is a good way to show off the dynamic range performance of the Sony IMX094 CMOS sensor for gearhead's self-satisfaction, because it heavily relies on gear which means not many other photographers will be able to do it properly. It simply rules out competition from any CCD user or Canon user.

There are of course advantages of 80MP CCD but I mostly see it inside a studio or for a low contrast scene outdoors where others have photographed many times already (because it does not rely on sensor DR performance heavily). For portrait in studio yes 80MP CCD gives you most joy for pixel-peeping, but for outdoors if you can bracket with a CCD then I can stitch with a CMOS and I can hardly see advantages of CCD other than an advantage in wide-angle compatibility (soon to be removed by larger version of Sony A7R-II's backside-illuminated CMOS sensor).

Regarding the halo effect in my image: that's the limitation of the software I used - it was a very old version ACR. If you push too much shadow in Capture One you also get the halo effect. It can be fixed by careful local adjustments if I had the time. Thanks for the criticism.
Title: Re: Best ISO for IQ280
Post by: JoeKitchen on July 06, 2015, 07:44:46 pm
This is where online forums suck, and I was being part of the problem today.

If everyone in this thread were to meet up at a bar and talk this out while looking at each other, I feel the tone of this discussion would have been different.  Words only account for 17% of communication, and, when we only see words, we tend to assume the most polarized meaning.  Not to mention, Voidshatter's first language is not English, which means I was probably mis-interrupting his intentions due to the nuances of the language, something that would not have happened in person.

After looking over the posts again, overall I think Voidshatter had some good points, and I am going to assume you (voidshatter) were not being hostel.
Title: Re: Best ISO for IQ280
Post by: gagemanning on July 06, 2015, 08:53:36 pm
I never realized I would cause such a huge debate.  Honestly, it's hard for me to get into the technical stuff (pixel peeping, etc...).  My eyes are not attune to such testing.  I can definitely see when noise is present and that is why I asked the question if there was much difference between the 2 (also wanted to make sure it did not effect the dynamic range).

Thanks everyone for there input.  I've learned a lot.   :)

gage
Title: Re: Best ISO for IQ280
Post by: Ken R on July 06, 2015, 09:14:02 pm
This is where online forums suck, and I was being part of the problem today.

If everyone in this thread were to meet up at a bar and talk this out while looking at each other, I feel the tone of this discussion would have been different.  Words only account for 17% of communication, and, when we only see words, we tend to assume the most polarized meaning.  Not to mention, Voidshatter's first language is not English, which means I was probably mis-interrupting his intentions due to the nuances of the language, something that would not have happened in person.

After looking over the posts again, overall I think Voidshatter had some good points, and I am going to assume you (voidshatter) were not being hostel.

I concur.

English is not my first language either and I understand that sometimes some things are lost in translation but voidshatter has a quite a history of posting in this and other forums and he has a habit of hammering in his point of view no matter what and has quite a bit of underlying hate towards PhaseOne (other posters have this as well), on purpose or not it is there in a lot of his posts.

Does voidshatter speak the truth about some aspects of sensor performance? Yes, never said otherwise. It is just that he reduces photography gear and photography to just a few parameters and basically anything else than the Sony sensors is junk.

His discourse turns productive people away from posting in this and other forums. Not his information and tests which are nice but the tone and overall online demeanor. That is the personal aspect. You need at least some amount of cordiality and tact. Yes, even when one is behind a computer.

He might better serve a digital sensor / camera company behind the scenes in the technical development department. Back of house, not front of house.
Title: Re: Best ISO for IQ280
Post by: sbernthal on July 07, 2015, 01:19:50 am
This is where online forums suck, and I was being part of the problem today.

After looking over the posts again, overall I think Voidshatter had some good points, and I am going to assume you (voidshatter) were not being hostel.

I don't think you were part of the problem, and you are being very positive towards this guy who doesn't deserve it.

A few quotes from this thread:

"For your use case in the studio, the ISO 35 setting is merely a "+1.5EV exposure compensation for flash" for people like you who have no clue about what is called native ISO." (He edited this out later but certainly never apologized for it and pretty much denied it)

"I don't know where your confidence is from but it is kinda funny that a Credo user can judge my gear."

Why would you dismiss such comments? I wouldn't.
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 07, 2015, 01:48:33 am
Hi Paul,

My take is that there is not a lot of difference between modern CMOS and CCD in that sense. Both are mostly ISO-less. There is some gain in image quality with increasing ISO versus underexposure but it is very small. Canon cameras and Nikon D4 work differently, probably having a lot more analogue gain.

The Sony A7s has a couple of tricks in it's bag, helping at very high ISO's.

My take is that CMOS is improved in two areas, much reduced readout noise and a significant gain i well capacity, that is how many electron charges a pixel can hold.

Best regards
Erik

This is from the DxO Mark scores, on the IQ180.  They do rate the Phase iso's of 35, 50 and  100 as all at iso 29.

The problem as I see it is that photographers tend to use the same logic for iso increases on CCD and CMOS.  The issue on whether the iso on the Phase One CCD is really an increase? or is it just a metadata setting for C1 to use later on.  Unlike a CMOS iso increase which as I understand it, is an actual increase in gain on the chip.

There have been several comparisons of IQ180 iso 35 and iso 200 shots.  I tried to find the one done a few years ago, but was not able.  But the net, was that the image looked the same between a under exposed iso 35 by 2.5 stops  and a correctly exposed.  The two images when viewed side by side look pretty much the same noise levels etc.  (Note I may have this backwards, i.e. the iso 35 was even exposed but the iso 200 was under exposed)

I have put this question forward several times on various forums but it's never really been answered very clearly.  From reading various posts by users (as I have never found anything written officially by Phase One) is that you really don't change the gain on a CCD by pushing the iso but I am not qualified enough to know the answer.

I my use, (P45+, IQ160, IQ260, and IQ180), I feel that you can "push" the CCD maybe one stop, So on my IQ260, that would be either iso 50 to iso 100 or iso 100 to iso 200 depending on where you feel the real base iso rests.  In normal exposure ranges say 1" to 1/250th most times I will not see much difference between iso 50 or iso 100 on my 260.  What makes the difference to me is say the difference in shutter speeds, say 1/60 vs 1/125 at F11.  Just that one shutter speed difference can make a big difference in the noise in the shadows.  CCD needs light and lots of it and trying to push it on a dim day or late/early morning to me is not a good solution vs taking a longer exposure.

By the time you get to iso 200 on the IQ260 I feel that the shadows show quite a bit of noise and color loss, but areas that have good light can still allow for a very good clean shot, but I know I won't be able to push the shadows at all.  By iso 400, there is loss in color/sat thought the file.  Areas that were brightly exposed might allow for some recovery in post, but the loss in details can't be pulled back.

Of course moving to sensor plus changes all of this un to around iso 800.  But the loss in resolution makes this something I rarely do.

Paul Caldwell

Title: Re: Best ISO for IQ280
Post by: Steve Hendrix on July 07, 2015, 04:17:42 pm
I don't think you were part of the problem, and you are being very positive towards this guy who doesn't deserve it.

A few quotes from this thread:

"For your use case in the studio, the ISO 35 setting is merely a "+1.5EV exposure compensation for flash" for people like you who have no clue about what is called native ISO." (He edited this out later but certainly never apologized for it and pretty much denied it)

"I don't know where your confidence is from but it is kinda funny that a Credo user can judge my gear."

Why would you dismiss such comments? I wouldn't.

I agree - I'm not sure how one can attribute "people like you who have no clue" to language nuances...

Steve Hendrix
Capture Integration
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 07, 2015, 04:34:41 pm
Hi Steve,

I definitively see your point. Thanks for chiming in, but I feel that you would be a very good person to put things straight for the original poster. So I hope you share your knowledge on the issue…

Best regards
Erik

I agree - I'm not sure how one can attribute "people like you who have no clue" to language nuances...

Steve Hendrix
Capture Integration
Title: Re: Best ISO for IQ280
Post by: Steve Hendrix on July 07, 2015, 06:41:21 pm
Hi Steve,

I definitively see your point. Thanks for chiming in, but I feel that you would be a very good person to put things straight for the original poster. So I hope you share your knowledge on the issue…

Best regards
Erik

I don't discount what VS says necessarily, but I think what he is trying - perhaps - to communicate is a relatively moot point to some users, who have described how shooting at different ISO and therefore different shutters speeds impacts their work, which means perhaps in some situations ISO 100 and ISO 35 might be a wash, but being able to shoot at ISO 35 may come into play with certain shooting situations. And in that sense, not a case of a manufacturer trying to "cheat" or present some fake benefit.

Steve Hendrix
CI
Title: Re: Best ISO for IQ280
Post by: eronald on July 07, 2015, 08:13:03 pm
Hi Steve,

I mean no offense and I have no intention to troll here. Would you care to explain why Phase One's CCD digital backs are severely underexposing at higher ISOs when compared against Canon, Nikon and Sony cameras? Did Phase One deliberately bluff to fool the customers? Why can't they be honest to make the manufacturer's ISO match the measured ISO more closely so that the plot can match the nominal line? ISO 1600 of the IQ180 is only as bright as ISO 640 of a Canon/Nikon/Sony. Are they afraid of something?

It's a base-level ISO 25 or 35 back, rated at 100 ISO base to protect the highlights. Thanks to the excellent DR -by the standards of days bygone- the operator had good DR and was still protected against highlight overexpsoure, in other words the correction latitude goes two stops both ways.

Edmund
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 07, 2015, 08:27:56 pm
It's a base-level ISO 25 or 35 back, rated at 100 ISO base to protect the highlights. Thanks to the excellent DR -by the standards of days bygone- the operator had good DR and was still protected against highlight overexpsoure, in other words the correction latitude goes two stops both ways.

Edmund

Then why do they cease offering as much highlight protection for lower ISO settings such like 35 and 50? Is this a kind of deception? If the user was to trust the numbers from Phase One's ISO settings and do metering accordingly, then ISO 35 has 1.5 stops less protection against highlight than ISO 100 does. Why?
Title: Re: Best ISO for IQ280
Post by: Ken R on July 07, 2015, 09:03:58 pm
Then why do they cease offering as much highlight protection for lower ISO settings such like 35 and 50? Is this a kind of deception? If the user was to trust the numbers from Phase One's ISO settings and do metering accordingly, then ISO 35 has 1.5 stops less protection against highlight than ISO 100 does. Why?

...because
Title: Re: Best ISO for IQ280
Post by: eronald on July 07, 2015, 09:10:46 pm
Then why do they cease offering as much highlight protection for lower ISO settings such like 35 and 50? Is this a kind of deception? If the user was to trust the numbers from Phase One's ISO settings and do metering accordingly, then ISO 35 has 1.5 stops less protection against highlight than ISO 100 does. Why?

Because it is designed to be shot somewhere around ISO 100.

It can be shot at 35 or 400, and in either case you lose 2 stops latitude up or down, compared with the optimal design performance at ISO 100, but you still get VERY good images.

If I hold a fountain pen sideways, it also writes differently.

Now if you want to say that Lucifer and Beezlebub or whatever the Phase dealers present on this forum call themselves these days put a bit of lipstick on the pig, that is a different issue, but actually for creatures of the darkness I find them rather forthright, and they always seem to deliver value for kidney.

Edmund
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 07, 2015, 09:27:32 pm
Because it is designed to be shot somewhere around ISO 100.

It can be shot at 35 or 400, and in either case you lose 2 stops latitude up or down, compared with the optimal design performance at ISO 100, but you still get VERY good images.

If it is designed to be shot around ISO 100, then why does Phase One hide the fact that ISO 35 is extended ISO? Why do they offer only as low as ISO 50 (as extended ISO as well I bet) for the IQ3 80MP, instead of ISO 35 for the IQ280?
Title: Re: Best ISO for IQ280
Post by: BernardLanguillier on July 07, 2015, 10:07:21 pm
If it is designed to be shot around ISO 100, then why does Phase One hide the fact that ISO 35 is extended ISO? Why do they offer only as low as ISO 50 (as extended ISO as well I bet) for the IQ3 80MP, instead of ISO 35 for the IQ280?

It is not. ISO35 is the real base ISO. But since most shooters using backs prefer to avoid burning highlights, the recommended ISO is ISO100 which - as Edmund correctly explained - is a planned under-exposure by 1.5 stops that is compensated in the back preview and in raw conversion and provides amazing highlight "recovery".

This is mostly where the reputation of backs having amazing DR is coming from. There are still many MFDB shooters who will swear to you that their CCD backs behave differently than DSLRs in terms of highlight "recovery".

I don't see any issue, this has been known for years and it has served most back users and Phaseone very well.

- If you are a middle of the road shooter in studio environment, then use ISO 100 and be sure you will never run into un-recoverable burned highlights,
- If you are doing landscape/architecture with a back, then shoot at ISO35 and do ETTR.

I am not sure why you seem to consider this as a major conspiracy, this isn't any close to rocket science.

Cheers,
Bernard
Title: Re: Best ISO for IQ280
Post by: eronald on July 07, 2015, 10:08:02 pm
If it is designed to be shot around ISO 100, then why does Phase One hide the fact that ISO 35 is extended ISO? Why do they offer only as low as ISO 50 (as extended ISO as well I bet) for the IQ3 80MP, instead of ISO 35 for the IQ280?

Actually the 35 would be the true base ISO of the CCD if you apply ETTR. Which of course most of us wouldn't do for studio work, because we need the highlight detail in the speculars.
Title: Re: Best ISO for IQ280
Post by: eronald on July 07, 2015, 10:09:49 pm
Bernard,

Such eloquence. You are wasted as a photographer. Become a speechwriter instead.
Or maybe Beezelbub and Lucifer should hire you for their new Tokyo office. :)

E.

It is not. ISO35 is the real base ISO. But since most shooters using backs prefer to avoid burning highlights, the recommended ISO is ISO100 which - as Edmund correctly explained - is a planned under-exposure by 1.5 stops that is compensated in the back preview and in raw conversion and provides amazing highlight "recovery".

This is mostly where the reputation of backs having amazing DR is coming from. There are still many MFDB shooters who will swear to you that their CCD backs behave differently than DSLRs in terms of highlight "recovery".

I don't see any issue, this has been known for years and it has served most back users and Phaseone very well.

- If you are a middle of the road shooter in studio environment, then use ISO 100 and be sure you will never run into un-recoverable burned highlights,
- If you are doing landscape/architecture with a back, then shoot at ISO35 and do ETTR.

I am not sure why you seem to consider this as a major conspiracy, this isn't any close to rocket science.

Cheers,
Bernard

Title: Re: Best ISO for IQ280
Post by: voidshatter on July 07, 2015, 10:17:51 pm
It is not. ISO35 is the real base ISO. But since most shooters using backs prefer to avoid burning highlights, the recommended ISO is ISO100 which - as Edmund correctly explained - is a planned under-exposure by 1.5 stops that is compensated in the back preview and in raw conversion and provides amazing highlight "recovery".

This is mostly where the reputation of backs having amazing DR is coming from. There are still many MFDB shooters who will swear to you that their CCD backs behave differently than DSLRs in terms of highlight "recovery".

I don't see any issue, this has been known for years and it has served most back users and Phaseone very well.

- If you are a middle of the road shooter in studio environment, then use ISO 100 and be sure you will never run into un-recoverable burned highlights,
- If you are doing landscape/architecture with a back, then shoot at ISO35 and do ETTR.

I am not sure why you seem to consider this as a major conspiracy, this isn't any close to rocket science.

Cheers,
Bernard

If ISO 35 is "the real base ISO for IQ280" then why does Phase One only offer ISO 50 for the IQ3 80MP?

Did Phase One advise or specify when to use ISO 35 (e.g. landscape/architecture) and when to use ISO 100 (e.g. portrait in studio) in their manuals or at their website? Or this is common sense assumed to be well known? This doesn't make sense to me. Landscape could also benefit from extra highlight protection. Why should landscape be shot at ISO 35? According to your logic, any Canon/Nikon/Sony user who doesn't shoot landscape/architecture at the extended ISO setting of their camera is silly? e.g. D810 at ISO 64 offers more highlight protection than ISO 32 - while most people shoot landscape at ISO 64, are you saying that most landscape photographers are not using gear properly?
Title: Re: Best ISO for IQ280
Post by: eronald on July 07, 2015, 10:29:29 pm
If ISO 35 is "the real base ISO for IQ280" then why does Phase One only offer ISO 50 for the IQ3 80MP?

Did Phase One advise or specify when to use ISO 35 (e.g. landscape/architecture) and when to use ISO 100 (e.g. portrait in studio) in their manuals or at their website? Or this is common sense assumed to be well known? This doesn't make sense to me. Landscape could also benefit from extra highlight protection. Why should landscape be shot at ISO 35? According to your logic, any Canon/Nikon/Sony user who doesn't shoot landscape/architecture at the extended ISO setting of their camera is silly? e.g. D810 at ISO 64 offers more highlight protection than ISO 32 - while most people shoot landscape at ISO 64, are you saying that most landscape photographers are not using gear properly?

Maybe you should tell us - you seem to have a line to "most landscape photographers". As for me, I wouldn't recognise a landscape if it bit me in the ass.

Edmund
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 07, 2015, 10:37:17 pm
Maybe you should tell us - you seem to have a line to "most landscape photographers". As for me, I wouldn't recognise a landscape if it bit me in the ass.

Edmund

Let me ask a very specific question:

a) Nikon explicitly specifies that the real base ISO for the Nikon D810 is ISO 64 (with ISO 32 as extended ISO).

b) Bernard and many others here believe that the real base ISO for the Phase One IQ280 is ISO 35.

Why do they think that ISO 35 is the real base ISO for the IQ280, while ISO 32 is officially not the real base ISO for the D810? What is the difference here?

If you ask for my opinion, I would say that the real base ISO for the IQ280 is ISO 100 (with ISO 35 and ISO 50 as extended ISO).
Title: Re: Best ISO for IQ280
Post by: Paul2660 on July 07, 2015, 10:49:23 pm
Because it is designed to be shot somewhere around ISO 100.

It can be shot at 35 or 400, and in either case you lose 2 stops latitude up or down, compared with the optimal design performance at ISO 100, but you still get VERY good images.

If I hold a fountain pen sideways, it also writes differently.

Now if you want to say that Lucifer and Beezlebub or whatever the Phase dealers present on this forum call themselves these days put a bit of lipstick on the pig, that is a different issue, but actually for creatures of the darkness I find them rather forthright, and they always seem to deliver value for kidney.

Edmund

Following this explanation which makes sense to me based on my experience, what would be the optimal design iso performance for the 60Mp backs, which start at 50?  I can see the push to 100 as I do it often, but by 200, in my images where you still have good highlight protection, I feel the images really suffer in the shadows, i.e. excessive noise.  So I still tend to bracket most series knowing that one of the shots will be the correct one.  But to me the other side of the equation is good light for the CCD, i.e correct exposure and this becomes even more critical on shifts/movements.  The difference in say 1/60 and 1/125 @ F11 on a 15mm shift can be huge in the difference in details that are captured, and not lost to noise.  This is something I see every time I use a Phase back.  The image must have the correct or near correct exposure for the critical parts of the image, where as with a CMOS capture I have the confidence I can expose for the highlights and pull up the shadows and still have details in them, with only 1 series of exposures.

The information in the later part of this post has been very informative.

Thanks to all.

Paul
Title: Re: Best ISO for IQ280
Post by: eronald on July 07, 2015, 10:54:59 pm
Following this explanation which makes sense to me based on my experience, what would be the optimal design iso performance for the 60Mp backs, which start at 50?  I can see the push to 100 as I do it often, but by 200, in my images where you still have good highlight protection, I feel the images really suffer in the shadows, i.e. excessive noise.  So I still tend to bracket most series knowing that one of the shots will be the correct one.  But to me the other side of the equation is good light for the CCD, i.e correct exposure and this becomes even more critical on shifts/movements.  The difference in say 1/60 and 1/125 @ F11 on a 15mm shift can be huge in the difference in details that are captured, and not lost to noise.  This is something I see every time I use a Phase back.  The image must have the correct or near correct exposure for the critical parts of the image, where as with a CMOS capture I have the confidence I can expose for the highlights and pull up the shadows and still have details in them, with only 1 series of exposures.

The information in the later part of this post has been very informative.

Thanks to all.

Paul

Paul,

The lower you rate the back, the better, although of course you really need to get the highlights right. The reason is that with a shift lens the sin^4 law (vignetting) lowers the exposure more and more in the far edge, and even if one *can* push, one is then eating into the shadow latitude. However, leading edge is exposed brighter, until you've shifted completely past the center, eg. using a 4x5 lens on a 36x38 back to make a pano.

The measured T stop of the lens depends on the measurement position on the sensor, and the degree of shift.

If you really shift all the way, you need to lower the assumed ISO of the back more and more, because now the lightmeter ISO has nothing to do with the back ISO due to the shift. It's not really the back ISO which is changing, in fact it is the real T-stop of the shifted lens, but it's simpler, I guess to think in terms of ISO.

I'm not the sharpest knife in the box here, as we all know, but Erik or Bart will do the sums for you. Anyway, at 5 am. I don't expect much of myself in terms of making sense :)

Edmund
Title: Re: Best ISO for IQ280
Post by: BernardLanguillier on July 07, 2015, 11:56:55 pm
If ISO 35 is "the real base ISO for IQ280" then why does Phase One only offer ISO 50 for the IQ3 80MP?

Did Phase One advise or specify when to use ISO 35 (e.g. landscape/architecture) and when to use ISO 100 (e.g. portrait in studio) in their manuals or at their website? Or this is common sense assumed to be well known? This doesn't make sense to me. Landscape could also benefit from extra highlight protection. Why should landscape be shot at ISO 35? According to your logic, any Canon/Nikon/Sony user who doesn't shoot landscape/architecture at the extended ISO setting of their camera is silly? e.g. D810 at ISO 64 offers more highlight protection than ISO 32 - while most people shoot landscape at ISO 64, are you saying that most landscape photographers are not using gear properly?

The base ISO is the one offering the maximum dynamic range, and therefore the lowest amount of noise.

Contrasty subject such as landscape demand the highest possible amount of DR. Because of this, they should be shot at the true base ISO. But there is another reason why you want to shoot landscape at the base ISO. This second reason is you want to perform ETTR to maximize the usage of available DR, and ETTR is easier to execute at the true base ISO of the camera, 35 ISO for the IQ280 and 64 ISO for the D810, because this the ISO at which the in camera histogram provides the most useful information about highlight clipping.

I disagree with your statement that landscape also benefits from highlight protection. If DR is finite, and it typically is, you want to maximize the usage of available DR by exposing to the right. Under-exposing, which is what you do when shooting at ISO 100 on a IQ280, results in wasting valuable stops in the shadows and you don't know you are under-exposing when shooting at ISO 100 with an IQ280 because the histogram is corrected not to show this to you.

Cheers,
Bernard
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 08, 2015, 12:05:42 am
The base ISO is the one offering the maximum dynamic range, and therefore the lowest amount of noise.

Contrasty subject such as landscape demand the highest possible amount of DR. Because of this, they should be shot at the true base ISO. But there is another reason why you want to shoot landscape at the base ISO. This second reason is you want to perform ETTR to maximize the usage of available DR, and ETTR is easier to execute at the true base ISO of the camera, 35 ISO for the IQ280 and 64 ISO for the D810, because this the ISO at which the in camera histogram provides the most useful information about highlight clipping.

I disagree with your statement that landscape also benefits from highlight protection. If DR is finite, and it typically is, you want to maximize the usage of available DR by exposing to the right. Under-exposing, which is what you do when shooting at ISO 100 on a IQ280, results in wasting valuable stops in the shadows and you don't know you are under-exposing when shooting at ISO 100 with an IQ280 because the histogram is corrected not to show this to you.

Cheers,
Bernard

So I guess you are still not aware of the fact that:

a) For the IQ280 ISO 35 has the same total dynamic range as ISO 100;
b) For the D810 ISO 32 has the same total dynamic range as ISO 64.

If you disagree with the above fact, then please supply raw files as evidence to disprove;

If you agree with the above, then please answer why do you think ISO 35 is true base for IQ280 while ISO 32 is not true base for D810?
Title: Re: Best ISO for IQ280
Post by: eronald on July 08, 2015, 12:08:26 am
The base ISO is the one offering the maximum dynamic range, and therefore the lowest amount of noise.

Contrasty subject such as landscape demand the highest possible amount of DR. Because of this, they should be shot at the true base ISO. But there is another reason why you want to shoot landscape at the base ISO. This second reason is you want to perform ETTR to maximize the usage of available DR, and ETTR is easier to execute at the true base ISO of the camera, 35 ISO for the IQ280 and 64 ISO for the D810, because this the ISO at which the in camera histogram provides the most useful information about highlight clipping.

I disagree with your statement that landscape also benefits from highlight protection. If DR is finite, and it typically is, you want to maximize the usage of available DR by exposing to the right. Under-exposing, which is what you do when shooting at ISO 100 on a IQ280, results in wasting valuable stops in the shadows and you don't know you are under-exposing when shooting at ISO 100 with an IQ280 because the histogram is corrected not to show this to you.

Cheers,
Bernard

At least, I think the histo on the Phase back is a true Raw histo. Would the one on the Nikon be one of those toycam Jpeg imaginary histograms which ensures every image with a flower in it is blown out?

Edmund
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 08, 2015, 12:19:48 am
At least, I think the histo on the Phase back is a true Raw histo. Would the one on the Nikon be one of those toycam Jpeg imaginary histograms which ensures every image with a flower in it is blown out?

Edmund

The IQ3 series is advertised to offer a function for real histogram based on RAW. This is not true for the IQ2 series. Neither ISO 50 nor ISO 100 gives the correct highlight warning in playback for the IQ260 (which I assume would also be the case for the IQ280). The user has to rely on his own experience.

(https://yyj0wq.dm2302.livefilestore.com/y2pwgzX4lcvvkThvrI_kceAN33qazQTkOJhRHATbCZBOAaGPmpvgAPHNiyRt0H5x8Z3aHg0oOG2PrKEIJXY3wu9lotOdgyJvrMtedgptIzucbE/DSC01759.jpg?psid=1)

(https://yyj0wq.dm2302.livefilestore.com/y2pWDsw_GyUnE2sgBVOWKepqjnMMbGBFYMmNJLrBL3VrghNkZCOlWb8VIrBh8tIEg-_0IDmb2EFvhVnb-csFEy4bfP8PPOcL_lQZASQ9l2aImg/DSC01760.jpg?psid=1)

(https://yyipzg.dm2302.livefilestore.com/y2pH2GcOYKpjpQfvKXA6twbGCjzzpZe-k9SEf3J6UXfXrW7r0b7CxkIcknSOiDnkLfsEDa5mM1dcKHkmSwqztaN2ob9VCAzWmZPS79vWkyGqJU/iq260_iso_normal.JPG?psid=1)
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 08, 2015, 12:46:33 am
Hi Bernard,

I would suggest that you are right, except that we don't really know what the histograms shows and neither do we know what the camera/back does with the raw file. With a huge range of values (1- 65536) it would make a lot of sense just leave the raw file alone when increasing ISO, and that may be what the DxO-mark data indicates on the IQ-180.

Another issue the "film curve" that C1 applies as default to the raw image. This curve pushes highlights and makes the highlight region nonlinear. So, even an ETTR image may look to bright and having compressed highlights with C1. At least, that is my experience. Other converters also apply tonal compression, it is needed when mapping contrast scenery to low contrast media. But, at least with my P45+, film curve will be much brighter than linear in C1. In LR6 it seems that changing tone curve preserves brightness.

So, what I see is that the Phase One toolchain essentially protects highlights. LR on the other hand gladly applies highlight recovery, without giving any information and applies some default exposure correction.

On both the P45+ and on the Sonys I have the in camera/back histogram is better than its reputation. When I expose ETTR on the camera histogram the resulting raw histogram in RawDigger is pretty close to ETTR, while histograms in both C1 and LR6 are misrepresented (compared to RawDigger). I feel raw converters should have an option to show the unmanipulated raw histogram.

Best regards
Erik

The base ISO is the one offering the maximum dynamic range, and therefore the lowest amount of noise.

Contrasty subject such as landscape demand the highest possible amount of DR. Because of this, they should be shot at the true base ISO. But there is another reason why you want to shoot landscape at the base ISO. This second reason is you want to perform ETTR to maximize the usage of available DR, and ETTR is easier to execute at the true base ISO of the camera, 35 ISO for the IQ280 and 64 ISO for the D810, because this the ISO at which the in camera histogram provides the most useful information about highlight clipping.

I disagree with your statement that landscape also benefits from highlight protection. If DR is finite, and it typically is, you want to maximize the usage of available DR by exposing to the right. Under-exposing, which is what you do when shooting at ISO 100 on a IQ280, results in wasting valuable stops in the shadows and you don't know you are under-exposing when shooting at ISO 100 with an IQ280 because the histogram is corrected not to show this to you.

Cheers,
Bernard

Title: Re: Best ISO for IQ280
Post by: voidshatter on July 08, 2015, 12:58:39 am
Just did another test on the Nikon D4S to see how the in-camera playback works - apparently neither ISO 50 nor ISO 100 can correctly report the highlight clipping. Actually ISO 50 gave more accuracy. According to Bernard's logic, the real base native ISO is 50 for the Nikon D4S (which is against Nikon's official specification).
Title: Re: Best ISO for IQ280
Post by: BernardLanguillier on July 08, 2015, 01:06:29 am
So I guess you are still not aware of the fact that:

a) For the IQ280 ISO 35 has the same total dynamic range as ISO 100;
b) For the D810 ISO 32 has the same total dynamic range as ISO 64.

If you disagree with the above fact, then please supply raw files as evidence to disprove;

If you agree with the above, then please answer why do you think ISO 35 is true base for IQ280 while ISO 32 is not true base for D810?

You need to take into account the 2 aspects I mentioned above:
- DR
- Metering/ability to expose in a standard way (meaning resulting in expected raw values).

As far as DR goes, I don't have data and DxO didn't do the test at ISO 32, but I remember Nikon and others reporting that the DR at 32 ISO was lower than that at 64 ISO.

But they probably consider the combination of sensor behavior and camera metering when stating this. At 32 ISO, the D810 will basically over-expose by 2/3 of a stop (32 vs 49 real) compare to what it would do at 64 ISO since they cannot lower the gain further.

So the level of exposure in the raw data will be the expect one when looking at an 35 ISO shot in the IQ280 while it is going to be 2/3 stop brighter in the D810 files. This is the reason why I am saying that the true base ISO of the IQ280 is 35 and 64 with the D810.

Apologies, I'll have to drop out now. Keeping having fun! ;)

Cheers,
Bernard
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 08, 2015, 01:20:48 am
Hi Steve,

My point was not really discussing Void's findings, but merely hoping for a good answer to the question of the OP, which is the best ISO to use with the IQ280?

Personally, I would presume that lowest ISO is best in most cases, combined with good understanding of in camera histogram. I would also suggest to check out raw histograms with a good tool like RawDigger. But I have only a P45+ and some Sony cameras. IQ280 may be quite a bit different.

Best regards
Erik

I don't discount what VS says necessarily, but I think what he is trying - perhaps - to communicate is a relatively moot point to some users, who have described how shooting at different ISO and therefore different shutters speeds impacts their work, which means perhaps in some situations ISO 100 and ISO 35 might be a wash, but being able to shoot at ISO 35 may come into play with certain shooting situations. And in that sense, not a case of a manufacturer trying to "cheat" or present some fake benefit.

Steve Hendrix
CI
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 08, 2015, 01:25:11 am
You need to take into account the 2 aspects I mentioned above:
- DR
- Metering/ability to expose in a standard way (meaning resulting in expected raw values).

I have already shown that neither the IQ260 nor the D4S can offer accurate highlight clip warnings in playback in camera regardless of whatever ISO setting used.

As far as DR goes, I don't have data and DxO didn't do the test at ISO 32, but I remember Nikon and others reporting that the DR at 32 ISO was lower than that at 64 ISO.

But they probably consider the combination of sensor behavior and camera metering when stating this. At 32 ISO, the D810 will basically over-expose by 2/3 of a stop (32 vs 49 real) compare to what it would do at 64 ISO since they cannot lower the gain further.

a) In your logic do you mean DxO has underestimated the true performance of the IQ180 by not reporting the dynamic range at ISO 35?

b) I now supply my evidence by means of RAW files to prove that for D4S the dynamic range is identical for ISO 50 and ISO 100: dropbox link click here (https://www.dropbox.com/sh/h0hgl5nktp8ptmf/AADTJRrYcWHrfA0H2LYnrvQNa?dl=0). Where is your proof of ISO 32 having lower dynamic range than ISO 64 for D810?

c) Bill Claff (http://home.comcast.net/~NikonD70/Charts/PDR.htm) reports dynamic range as below: ISO 50 and ISO 100 perform the same on the IQ260, while ISO 32 and ISO 64 perform the same on the D810.

So the level of exposure in the raw data will be the expect one when looking at an 35 ISO shot in the IQ280 while it is going to be 2/3 stop brighter in the D810 files. This is the reason why I am saying that the true base ISO of the IQ280 is 35 and 64 with the D810.

Apologies, I'll have to drop out now. Keeping having fun! ;)

Cheers,
Bernard

As far as I know, the level of exposure in the RAW data can only be verified by RawDigger. In-camera playback, Capture One, ACR etc are not reliable.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 08, 2015, 01:39:58 am
Hi Steve,

My point was not really discussing Void's findings, but merely hoping for a good answer to the question of the OP, which is the best ISO to use with the IQ280?

Personally, I would presume that lowest ISO is best in most cases, combined with good understanding of in camera histogram. I would also suggest to check out raw histograms with a good tool like RawDigger. But I have only a P45+ and some Sony cameras. IQ280 may be quite a bit different.

Best regards
Erik

According to my tests of highlight warnings inside the in-camera playback, Bernard is right, just use ISO 35 for landscape and ISO 100 for portrait in studio if the user is not familiar with the IQ280's highlight recoverability and he/she shoots untethered relying only on the in-camera playback. D810 users should also use ISO 32 for landscape.

I can't agree with his definition of "real base native ISO" though.
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 08, 2015, 02:17:42 am
Hi Ken,

I have never noticed…

I would say that some posters could consider being more polite (doesn't apply to you).

Another point may be that things are perhaps not confused by translation, but interpretation of technical terms. For instance, we talk about ISO, but ISO is a standard (or three standards), a setting on camera, a target value for exposure determination. How does ISO affect the raw data? Does the camera have variable pre-amps? Is the ISO data scaled. How does ISO setting affect histogram on the camera/back?  Just the term ISO can cause quite a lot of confusion.

Regarding "hate towards Phase One". I know that Void has an IQ-250, and I am pretty sure he is happy with it. He also sent me a whole bunch of raw files. Personally, I own a P45+ which is said be a good one, according to some owners/posters. I am using it quite a lot and I am generally happy with the results.

On the other hand, I don't feel that the results justify the high costs, and I think this is an experience worth sharing, too. Also, I could not really see the resolution advantage in prints. I normally print A2. In larger prints I would probably see advantage to the P45+, but as it happens I didn't make pictures with the P45+ I wanted to blow up really big.

I see three major advantages of the P45+/Hassy combination to my Sony gear, the first is the resolution advantage. The second is that I enjoy working with the classical equipment. The third advantage is that in many cases the 39x48 format of the P45+ is beneficial. For instance, the widest angle I have on the Hassy is the 40/4 Distagon, but it is less limitation than I originally expected.

On the other hand, I feel that MFD is to expensive in the long term. Repair prices on backs seem to be very high, and new backs are very expensive.

I will probably hang on to my Hasselblad and P45+, but I just ordered a Sony A7rII with two lenses, a Canon 24/3.5 T&S and a Batis 1.8/85. Camera + two lenses costs less than my back did two years ago (total outlay is around 8k$US and I paid 10k$US for the P45+ back). I could of course buy an IQ-150 or rather a Hasselblad VFC 50c and a technical camera with a couple of lenses and achieve about the same, albeit at a much higher costs.

Best regards
Erik

I concur.

English is not my first language either and I understand that sometimes some things are lost in translation but voidshatter has a quite a history of posting in this and other forums and he has a habit of hammering in his point of view no matter what and has quite a bit of underlying hate towards PhaseOne (other posters have this as well), on purpose or not it is there in a lot of his posts.

Does voidshatter speak the truth about some aspects of sensor performance? Yes, never said otherwise. It is just that he reduces photography gear and photography to just a few parameters and basically anything else than the Sony sensors is junk.

His discourse turns productive people away from posting in this and other forums. Not his information and tests which are nice but the tone and overall online demeanor. That is the personal aspect. You need at least some amount of cordiality and tact. Yes, even when one is behind a computer.

He might better serve a digital sensor / camera company behind the scenes in the technical development department. Back of house, not front of house.
Title: Re: Best ISO for IQ280
Post by: synn on July 08, 2015, 07:08:35 am
If a photon shat in a void and there's no one around to capture it, would ISO settings make a difference?
Title: Re: Best ISO for IQ280
Post by: eronald on July 08, 2015, 07:27:28 am
If a photon shat in a void and there's no one around to capture it, would ISO settings make a difference?

Hold your nose - presumably, the stink would spread at the speed of light.

Now, that was an abstract question ISO a philosopher to ask it. Come to think, maybe it should have been left unassked.

Edmund
Title: Re: Best ISO for IQ280
Post by: Christopher Sanderson on July 09, 2015, 07:41:37 am
If the tone of this discussion continues in this manner, the topic will be locked. Posters hidden behind pseudonyms will be banned.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 09, 2015, 09:16:50 am
Just realized that this forum requires real names, so I change my on-screen name from voidshatter to my real name.  ::)
Title: Re: Best ISO for IQ280
Post by: Christopher Sanderson on July 09, 2015, 09:52:33 am
The use of 'Real Names' is a strong suggestion (http://forum.luminous-landscape.com/index.php?topic=76496.0) but since there is no realistic way to police it, the suggestion cannot be an absolute requirement.

What this does suggest however is that there be a far stricter requirement of reasonable behaviour from those who use pseudonyms. Thus a stricter & quicker use of the ban.

Title: Re: Best ISO for IQ280
Post by: AlterEgo on July 09, 2015, 10:13:49 am
At least, I think the histo on the Phase back is a true Raw histo.
might be raw with per channel WB multipliers, but w/o further colorspace transforms (to sRGB/aRGB/you-name-it).. so "semi-raw"...
Title: choosing ISO exposure index settings on the IQ280: how its 35 and 100 differ
Post by: BJL on July 09, 2015, 10:59:53 am
Pardon me if that has already been made clear in the previous six pages of posts, but I prefer to skip the misunderstandings and acrimony in favor of trying to help the original poster answer the original question.

1) From data like that as DXO, it seems that the IQ280 uses the same "gain" or conversion ratio of "raw output levels per photo-electron" in producing its raw files at ISO Exposure Index [EI] settings from 35 to 100.  Beyond that, the gain goes up in proportion to the EI setting.

2) Thus, what changes between the ISO EI settings of 35 and 100 is:

(a) The way in-camera light meter chooses or recommends exposure levels: for example, with the same aperture setting and same lighting, when aperture priority at EI=35 chooses 1/35s, at EI=100 it will choose 1/100s.

(b) Extra information in the raw file will then recommend different conversion from raw levels to luminance levels in JPEG output to balance the above difference in default exposure levels and the consequent difference in raw level placement.

So the main difference is that, if you follow the in-camera metering recommended exposures (for example, using any auto-exposure mode with no exposure compensation) EI=35 chooses higher exposure levels and gives proportionately higher numerical raw levels, generally giving less highlight headroom but better shadow handling.  To decide which EI setting is "best", you must decide which trade-off you prefer, and I suspect that it depends on preferences for shutter speed, DOF, etc., so that there is no universal "best" choice between these two EI settings.

Aside: With a perfectly "ISO insensitive" camera, it could make sense to use this fixed conversion ratio all the time, avoiding variable gain analog amplifier circuits entirely, in favor of bit-shifting "digital gain" later.  That is, having the raw levels proportional to sensor photo-electron counts in a fixed way.  For all I know, the higher ISO EI settings of the IQ280 actually just bit shift the ADC output rather than there being any variable analog gain circuit, but perhaps Yunil or others will correct me on that.
Title: Re: Best ISO for IQ280
Post by: Ken R on July 09, 2015, 11:07:53 am
Sums it up it nicely:

:)
Title: Re: Best ISO for IQ280
Post by: Guillermo Luijk on July 09, 2015, 12:07:44 pm
6 pages just to discuss two fake ISO values? come on, this happens since Canon 5D's ISO50 back 10 years ago.

For a given exposure (aperture/shutter pair) ISO35 and ISO50 produce exactly the same RAW data as ISO100, so they are actually ISO100 electronic gains. Any observed difference in a regular application (camera JPEG clipping warning, resulting noise,...) is just the consequence of Phase One's differentiated metering when you select ISO35/ISO50 vs ISO100:
• ISO35 is just ISO100 overexposed by 1,5EV (with a camera JPEG corrected down by -1,5EV to look fine, with a bit less noise, but possibly with some blown highlights vs the ISO50 and ISO100 RAWs and JPEGs).
• ISO50 is just ISO100 overexposed by 1EV (with a camera JPEG corrected down by -1EV to look fine, with a bit less noise, but possibly with some blown highlights vs the ISO100 RAW and JPEG).

(http://www.guillermoluijk.com/misc/iq180.png)

Regards
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 09, 2015, 12:38:01 pm
Hi Guillermo,

I agree with what you posted, however some people here believe that ISO 35 is a very important advantage for their 80 MP Dalsa and use it as an excuse for not upgrading to IQ3 80MP. They believe it is different from (and definitely better than) Nikon D810's ISO 32.

Yunli
Title: Re: Best ISO for IQ280
Post by: BJL on July 09, 2015, 12:56:15 pm
6 pages just to discuss two fake ISO values? come on, this happens since Canon 5D's ISO50 back 10 years ago.

For a given exposure (aperture/shutter pair) ISO35 and ISO50 produce exactly the same RAW data as ISO100
so they are actually ISO100 electronic gains. . .  .
I agree so far, but
. . . so they are actually ISO100 electronic gains.
The DXO graph you show suggests instead that EI=35, 50, and 100 settings are all about ISO 29 gain, at least measured by the "low-balling" ISO SSat standard, which is what DXO calls "measured ISO".  Why do you say instead that that are all "actually ISO 100"?  Which of the various other ISO measurements are you referring to?

Some have argued that the EI=50 and 100 settings are instead "fake", but that misunderstands the intended function of the "ISO" setting.  Let me repeat once again: the "ISO" setting on cameras is an Exposure Index setting (as in ISO definition Standard Output Sensitivity and such) relating to AE mode operation, light metering, and level placement in default conversions to JPEG.  It is not a speed latitude rating, for which ISO defines SSat, S 40:1 and S10:1 -- SSat as the upper end of the exposure level latitude (lowest EI) and S40:1 and S10:1 as options for the lower end of the exposure level latitude (highest EI).

P. S. For comparison, DXO measures the D810 has having ISO SSat of 47 at its two lowest EI setting of 32 and 64, so in terms of highlight headroom, the D810's EI=32 is below spec on highlight headroom, and its EI=64 is about comparable to the IQ280's EI=35 in terms of highlight headroom, both having just a bit more than the minimum recommended by the ISO SSat spec for exposure latitude.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 09, 2015, 01:11:19 pm
I agree so far, butThe DXO graph you show suggests instead that EI=35, 50, and 100 settings are all about ISO 29 gain, at least measured by the "low-balling" ISO SSat standard, which is what DXO calls "measured ISO".  Why do you say instead that that are all "actually ISO 100"?  Which of the various other ISO measurements are you referring to?

Some have argued that the EI=50 and 100 settings are instead "fake", but that misunderstands the intended function of the "ISO" setting.  Let me repeat once again: the "ISO" setting on cameras is an Exposure Index setting (as in ISO definition Standard Output Sensitivity and such) relating to AE mode operation, light metering, and level placement in default conversions to JPEG.  It is not a speed latitude rating, for which ISO defines SSat, S 40:1 and S10:1 -- SSat as the upper end of the exposure level latitude (lowest EI) and S40:1 and S10:1 as options for the lower end of the exposure level latitude (highest EI).

P. S. For comparison, DXO measures the D810 has having ISO SSat of 47 at its two lowest EI setting of 32 and 64, so in terms of highlight headroom, the D810's EI=32 is below spec on highlight headroom, and its EI=64 is about comparable to the IQ280's EI=35 in terms of highlight headroom, both having just a bit more than the minimum recommended by the ISO SSat spec for exposure latitude.

Hi,

Two questions:

a) Do you think the IQ3 80MP is inferior as it can only shoot at as low as ISO 50 (which is far away from ISO 29 EI)?

b) DxO measures ISO 48 for Sony A99, however Sony's official specification explicitly specifies ISO 100 as the base native ISO. Do you think they are giving false information and they should revise their specification to ISO 50 instead for the base native ISO?

Title: Re: Best ISO for IQ280
Post by: Guillermo Luijk on July 09, 2015, 01:16:43 pm
I agree so far, butThe DXO graph you show suggests instead that EI=35, 50, and 100 settings are all about ISO 29 gain, at least measured by the "low-balling" ISO SSat standard, which is what DXO calls "measured ISO".  Why do you say instead that that are all "actually ISO 100"?  Which of the various other ISO measurements are you referring to?

OK I meant they are the same as that camera's ISO100, whatever the real ISO is. This is the only thing that matters IMO, answering the question: "can I get some advantage from those ISO35/50 as a RAW/JPEG shooter?".

Hi Guillermo,

I agree with what you posted, however some people here believe that ISO 35 is a very important advantage for their 80 MP Dalsa and use it as an excuse for not upgrading to IQ3 80MP. They believe it is different from (and definitely better than) Nikon D810's ISO 32.

In terms of DR the ISO35/50 add nothing to the ISO100, it's the same. The D810 at ISO32/64 (which are the same using the same trick) is one stop better than the MF back at ISO35/50/100. Another story is resolution, lenses,...

Regards

Title: Re: Best ISO for IQ280
Post by: BJL on July 09, 2015, 01:34:27 pm
Hi,

Two questions:

a) Do you think the IQ3 80MP is inferior as it can only shoot at as low as ISO 50 (which is far away from ISO 29 EI)?

b) DxO measures ISO 48 for Sony A99, however Sony's official specification explicitly specifies ISO 100 as the base native ISO. Do you think they are giving false information and they should revise their specification to ISO 50 instead for the base native ISO?

a) I do not know enough to say.  Does the IQ3 80MP have exactly the same sensor and the same SSat of 29?  If so, it is just a matter of convenience having an EI=35 setting, since using the exposure settings (aperture, shutter speed) at EI=50 will gave essentially the same data in the raw file, but perhaps needing different handling in raw conversion depending on how the raw converter uses the EI value tagged in the file.

b) No, I certainly do not think that Sony is giving false information: see my above comment that the "ISO" Exposure Index setting on a camera is not in any way intended to be equal to the SSat value, which is intended as a measure of the low end of the exposure latitude (a guideline for the maximum safe exposure level under typical lighting situations) not the ideal exposure level or the ideal placement of raw numerical levels!

It is one plausible approach (but not the only valid one) for a camera maker to set up its default AE operation to give about one stop more highlight headroom that the _minimum_ headroom recommend by the ISO standards for exposure latitude, by having its lowest EI setting one stop above the sensors base SSat value, and apparently Sony does that in the A99.  Olympus does similarly, and I am fine with that on my EM5; if I wish to "expose to the right" and flirt with blown highlights, I use careful light metering, exposure compensation, and raw conversion as appropriate. I would hate having a camera whose AE mode blows highlights any time that a scene has highlights more than three stops brighter than the metered average level, which is what happens if you expose at EI = SSat!
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 09, 2015, 01:39:50 pm
a) I do not know enough to say.  Does the IQ3 80MP have exactly the same sensor and the same SSat of 29?  If so, it is just a matter of convenience having an EI=35 setting, since using the exposure settings (aperture, shutter speed) at EI=50 will gave essentially the same data in the raw file, but perhaps needing different handling in raw conversion depending on how the raw converter uses the EI value tagged in the file.

b) No, I certainly do not think that Sony is giving false information: see my above comment that the "ISO" Exposure Index setting on a camera is not in any way intended to be equal to the SSat value, which is intended as a measure of the low end of the exposure latitude (a guideline for the maximum safe exposure level under typical lighting situations) not the ideal exposure level or the ideal placement of raw numerical levels!

It is one plausible approach (but not the only valid one) for a camera maker to set up its default AE operation to give about one stop more highlight headroom that the _minimum_ headroom recommend by the ISO standards for exposure latitude, by having its lowest EI setting one stop above the sensors base SSat value, and apparently Sony does that in the A99.  Olympus does similarly, and I am fine with that on my EM5; if I wish to "expose to the right" and flirt with blown highlights, I use careful light metering, exposure compensation, and raw conversion as appropriate. I would hate having a camera whose AE mode blows highlights any time that a scene has highlights more than three stops brighter than the metered average level, which is what happens if you expose at EI = SSat!

But I still don't understand why ISO 35 can be base setting for ISO 29 measured (IQ180), while ISO 50 cannot be base setting for ISO 48 measured (A99). Please explain? The standard you describe requires a headroom of just over ln(50/48)/ln(2) and less than ln(35/29)/ln(2) stops?
Title: Re: Best ISO for IQ280
Post by: BJL on July 09, 2015, 01:40:27 pm
OK I meant they are the same as that camera's ISO100, whatever the real ISO is. This is the only thing that matters IMO, answering the question: "can I get some advantage from those ISO35/50 as a RAW/JPEG shooter?".
Yes, this is the original, practical question!  And the answer seems to be:
(a) no, in that you can get the same results either way by choosing your aperture and shutter speed appropriately, but
(b) maybe yes if you rely on AE to chose exposure settings, in that they will favor more exposure at 35 or 50 than at 100 and so hopefully give less noise.
Title: Re: Best ISO for IQ280
Post by: Guillermo Luijk on July 09, 2015, 01:44:44 pm
(b) maybe yes if you rely on AE to chose exposure settings, in that they will favor more exposure at 35 or 50 than at 100 and so hopefully give less noise.

Less noise and more blown highlights. As long as the RAW shooter knows the story behind these ISO values and acts accordingly, all three are equivalent to him.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 09, 2015, 01:49:58 pm
Less noise and more blown highlights. As long as the RAW shooter knows the story behind these ISO values and acts accordingly, all three are equivalent to him.

Exactly. 8)
Title: Re: Best ISO for IQ280
Post by: Paul2660 on July 09, 2015, 03:21:48 pm
Not to sound like the child that had their head in their desk during class, but I am still trying to get my head around this.

I don't have the 180, (have shot it 5 or 6 times), but instead have the 260.  That back is base iso of 50.

So if I follow the information on this thread, it sound like the best overall iso setting on the 260 for highlight control would be iso 100 instead of 50.  50 might give a bit better shadow recovery, but 100 is going to give the best overall exposure?

The other elephant in the room that no one has mentioned is heat.  The CCD backs do get hot, and in the summer outdoor pretty quick if you are shooting in the sun with no shade over the back.  In my home state of Arkansas (US), the 5 months of May through September are hard on the 260.   If the back is on for over 20 minutes, which is common with a tech camera you will feel that top plate get hot, sometimes really hot. That heat seems to have a direct reflection on the noise in the shots so most times in the summer I will try to stay in the iso 50 range as it just seem to be a bit cleaner in push areas of a shot, even over iso 100.  That's just from my experience.  If you use zero latency, then the back heats up almost too much to hold, yes it can get really hot.

The other issue is if you use a tech camera/copal shutter lens, you are robbed of the 1/2 and 1/3 shutter speeds that a DF+ or XF would allow you.  These in-between shutter speeds sometimes can make just enough difference to give you a clean shot/manageable noise.

In my workflow, I work with water quite a bit, I prefer the slow shutter speeds for the blur effect.  Most times I am at iso 50 here, but I have often noticed that in areas of the greatest concentration of water, and where the light is the strongest, the Dalsa backs, seems to loose the fine details in the water.  I am not sure if this due to iso 50, and a bit of loss in overall highlight retention or something else.  But I will work with iso 100 next time out and see if I notice any differences.

Paul Caldwell

Title: Re: Best ISO for IQ280
Post by: voidshatter on July 09, 2015, 04:25:22 pm
Paul, base ISO for the IQ260 is 100 for normal mode and 200 for long exposure mode. ISO 50 in normal mode is indeed working at ISO 100, and ISO 140 is indeed working at ISO 200. ISO 50 and ISO 140 are just affecting your metering suggesting you to do more ETTR. If you are familiar with the highlight recoverability of the back you could use anything up to ISO 100 in normal mode, and anything up to ISO 200 in long exposure mode and still achieve the best results with a proper ETTR; otherwise just use the lowest possible ISO and check the highlight warnings.
Title: Re: Best ISO for IQ280
Post by: BJL on July 09, 2015, 06:16:00 pm
Less noise and more blown highlights. As long as the RAW shooter knows the story behind these ISO values and acts accordingly, all three are equivalent to him.
Yes: less noise and more risk of blown highlights.
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 09, 2015, 06:45:06 pm
Hi,

So what you say is that as long as exposure, that is f-stop, shutter speed and illumination is the same all the three low ISO settings give identical results, except the possibility that the raw converter applies different defaults or biases?

That would make a lot of sense.

Best regards
Erik

Less noise and more blown highlights. As long as the RAW shooter knows the story behind these ISO values and acts accordingly, all three are equivalent to him.
Title: Re: Best ISO for IQ280
Post by: Guillermo Luijk on July 09, 2015, 08:57:07 pm
So what you say is that as long as exposure, that is f-stop, shutter speed and illumination is the same all the three low ISO settings give identical results, except the possibility that the raw converter applies different defaults or biases?

That would make a lot of sense.

That is exactly what happens: the RAW data will be indistinguisable (this can easily be checked with DCRAW for instance), while the RAW metadata will inform the RAW developer about the needed clandestine exposure correction down (Baseline exposure metatag in DNG format) to create the illussion of ISO35/ISO50 being something different to ISO100.

Regards
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 09, 2015, 09:11:49 pm
That is exactly what happens: the RAW data will be indistinguisable (this can easily be checked with DCRAW for instance), while the RAW metadata will inform the RAW developer about the needed clandestine exposure correction down (Baseline exposure metatag in DNG format) to create the illussion of ISO35/ISO50 being something different to ISO100.

Regards

I have explained this for pages here and at getdpi but people just won't listen but instead defend their superiority of ISO 35 hard...
Title: IQ280 and A99 have minimum EI within ISO recommended limits, D810 no
Post by: BJL on July 10, 2015, 05:43:27 am
But I still don't understand why ISO 35 can be base setting for ISO 29 measured (IQ180), while ISO 50 cannot be base setting for ISO 48 measured (A99). Please explain? The standard you describe requires a headroom of just over ln(50/48)/ln(2) and less than ln(35/29)/ln(2) stops?
I skipped any debate about the Sony A99, or whether the IQ180 or A99 can use certain ISO EI settings, but since you ask: I see nothing wrong with the EI=50 on the A99.  What I am reporting on is a guideline on exposure latitude in the ISO 12232 standard that the SSat value is the minimum suggested exposure index setting (based roughly on giving three stops of highlight headroom: placing the metered luminance level at a raw level three stops below maximum.) Since 35>29 and 50>48, both are within that guideline.  It is the Nikon D810 minimum EI of 32 that falls outside it, with 32 being less that its SSat of 47 (as measured by DXO), so that EI setting gives about 1/2 stop less highlight headroom than the ISO suggested minimum.
Title: Re: Best ISO for IQ280
Post by: dchew on July 10, 2015, 07:45:40 am
I have explained this for pages here and at getdpi but people just won't listen but instead defend their superiority of ISO 35 hard...

Yunli,
I don't think anyone is really arguing the point that the raw data is the same for ISO 35, 50 and 100. As is so often the case with these debates, it seems to be one about semantics and tact. I happen to be in the BJL camp here. I don't see ISO 35 as a "fake" ISO. I see it as the only ISO that is "real". All the other ones are "fake." Therefore, I think of ISO 35 as the base ISO, and 50/100 (and all the others) as some sort of push. I think this is supported by the DXO graph. It is the ISO standard that leads me to this view. You may choose to look at it differently, which is fine by me. Just please don't bother trying to convince me that your perspective is the only one that is correct.

This is an interesting position for me to take because I've owned an IQ180 since they were first released (ordered Apr-2011 delivered Aug-2011). Some may remember when this back was first announced the base ISO was not 35. It was an early firmware release that provided the option for 35 ISO.

I do not agree with your position that this is some conspiracy on the part of PhaseOne. As Bernard stated, all this isn't rocket science; learn how the camera / back / histogram / metering works and shoot accordingly. I don't see this any differently than the old Velvia debate. Was it really ISO 50, or was it ISO 35 film?? Those who loved the saturated colors used it at 50. Those who wanted a more neutral result used it (carefully) at 35. Was 50 a conspiracy on the part of Fuji? Not to me, but think what you want.

You state your definition of proper exposure is to check with RawDigger. While I understand and appreciate that, as a landscape photographer I find it particularly difficult to do that in the field. What I do is use both ISO 35 and ISO 100. In order to be efficient for me I use ISO 35 when I am worried about shadow detail, and ISO 100 when worried about blowing highlights. I'm sure that sounds ridiculous to you, but that keeps me moving when the light is changing fast. I don't have a light meter in the field at all so I rely on my head and the histogram, which needs to be interpreted (especially my head).

What I find amusing about all this is the two photos below. I took these while backpacking in the Wind Rivers. Although I've posted them in other threads, I think they are useful in getting a point across. The first image was taken at sunset with IQ180/Alpa STC/90hrsw ISO 35. The second image was taken the next morning with Sony a7r/Leica 90 summicron ISO 100. Why did I use the Sony in the morning? Was it because I was worried about the wide dynamic range of this shot? No, it was because it was cold, I was in a hurry and I had a miserable sleepless night because of a nasty headache and buffeting winds against the tent all night. I figured I would drop half of the Alpa gear in my state at the time.

The point is at the end of the day it is the Sony image that has blown highlights and struggles with the dynamic range of the scene. So all of this debate pales in comparison to what subjects you like to shoot and what conditions you have to deal with.

To the OP I would offer this: If you are worried about highlights, use ISO 100. If you are worried about shadows use ISO 35. But most of all, do what gives you the best results given your workflow.

Dave

(http://www.davechewphotography.com/temp_images/windriverpost/DChew_140904_007713_p2-FrameShop.jpg)

(http://www.davechewphotography.com/temp_images/windriverpost/DChew_140905_01800_p1-FrameShop.jpg)
Title: Re: Best ISO for IQ280
Post by: Paul2660 on July 10, 2015, 08:17:15 am
Dave

Great shots. Love the top shot.

Paul
Title: Re: Best ISO for IQ280
Post by: DucatiTerminator on July 10, 2015, 11:17:05 am
+1

Alvin
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 10, 2015, 11:54:01 am
Hi Dave,

Great pictures…

I would essentially share your opinion. I am not shoot any IQ-backs, P45+ is the closest I get. My ISO setting is almost glued to base ISO. On the cameras I have, that is the P45+ and the Sony the histograms work pretty well. With the P45+ I don't use a light meter, just take a shot and adjust exposure until I have ETTR on the histogram and no blinkies. That works well for me mostly. I use RawDigger quite a lot, but it is a learning experience, just to learn about my exposures.

On the Sonys I use aperture priority and use compensation to get ETTR exposure.

Best regards
Erik

Yunli,
I don't think anyone is really arguing the point that the raw data is the same for ISO 35, 50 and 100. As is so often the case with these debates, it seems to be one about semantics and tact. I happen to be in the BJL camp here. I don't see ISO 35 as a "fake" ISO. I see it as the only ISO that is "real". All the other ones are "fake." Therefore, I think of ISO 35 as the base ISO, and 50/100 (and all the others) as some sort of push. I think this is supported by the DXO graph. It is the ISO standard that leads me to this view. You may choose to look at it differently, which is fine by me. Just please don't bother trying to convince me that your perspective is the only one that is correct.

This is an interesting position for me to take because I've owned an IQ180 since they were first released (ordered Apr-2011 delivered Aug-2011). Some may remember when this back was first announced the base ISO was not 35. It was an early firmware release that provided the option for 35 ISO.

I do not agree with your position that this is some conspiracy on the part of PhaseOne. As Bernard stated, all this isn't rocket science; learn how the camera / back / histogram / metering works and shoot accordingly. I don't see this any differently than the old Velvia debate. Was it really ISO 50, or was it ISO 35 film?? Those who loved the saturated colors used it at 50. Those who wanted a more neutral result used it (carefully) at 35. Was 50 a conspiracy on the part of Fuji? Not to me, but think what you want.

You state your definition of proper exposure is to check with RawDigger. While I understand and appreciate that, as a landscape photographer I find it particularly difficult to do that in the field. What I do is use both ISO 35 and ISO 100. In order to be efficient for me I use ISO 35 when I am worried about shadow detail, and ISO 100 when worried about blowing highlights. I'm sure that sounds ridiculous to you, but that keeps me moving when the light is changing fast. I don't have a light meter in the field at all so I rely on my head and the histogram, which needs to be interpreted (especially my head).

What I find amusing about all this is the two photos below. I took these while backpacking in the Wind Rivers. Although I've posted them in other threads, I think they are useful in getting a point across. The first image was taken at sunset with IQ180/Alpa STC/90hrsw ISO 35. The second image was taken the next morning with Sony a7r/Leica 90 summicron ISO 100. Why did I use the Sony in the morning? Was it because I was worried about the wide dynamic range of this shot? No, it was because it was cold, I was in a hurry and I had a miserable sleepless night because of a nasty headache and buffeting winds against the tent all night. I figured I would drop half of the Alpa gear in my state at the time.

The point is at the end of the day it is the Sony image that has blown highlights and struggles with the dynamic range of the scene. So all of this debate pales in comparison to what subjects you like to shoot and what conditions you have to deal with.

To the OP I would offer this: If you are worried about highlights, use ISO 100. If you are worried about shadows use ISO 35. But most of all, do what gives you the best results given your workflow.

Dave

(http://www.davechewphotography.com/temp_images/windriverpost/DChew_140904_007713_p2-FrameShop.jpg)

(http://www.davechewphotography.com/temp_images/windriverpost/DChew_140905_01800_p1-FrameShop.jpg)
Title: Re: Best ISO for IQ280
Post by: dchew on July 10, 2015, 12:46:47 pm
Thanks Paul, Alvin and Erik. I still do the "be there" part better than the "f/8" part or the creative part. But some day I will master this craft!

I don't often get involved in these debates, but it occurred to me that this back is four years old. About a year after using it I stopped carrying ND grads. Sure there are times when I wish I had them but they are few and far between. The new Sony sensors have wonderful dynamic range (and yes I will be getting the new a7rII). Do the IQ backs have poor dynamic range? Well, the answer is compared to what? I still jump for joy at how much they have compared to what I used to shoot (Velvia and Canon DSLR's), so I'm still slaphappy. It's kinda like saying a McLaren P1 has poor acceleration because a Porsche 918 gets to 60 mph in 2.4 seconds vs. 2.7 seconds (and of course the Porsche is cheaper too). But either one is an awful lot better than my Jeep! Unless of course I can get one of those cars to follow me through the Rubicon Trail.

Everything is relative.

Dave
Title: Re: Best ISO for IQ280
Post by: Paul2660 on July 10, 2015, 01:31:57 pm
Dave,

You bring up a good point, and after reading over this thread, I found myself going back to some of early 2008/2009 P45+ work, with the AFD III, non DF even and 35mm Mamiya lens.  I have been a bit negative on the old P45+, however after working some old files in both latest versions of LR and C1 vr 8, I have to say, I was impressed.  I have thousands and thousands of images from those years as I worked the hardest with the P45+, but had written off a lot of those trips thinking the DR of the P45+ was just not there.

However,, it is there as long as you follow pretty much the same rules that have been stated in this thread, and the P45+ does have an amazing look to the files, a bit refreshing.

Never thought I would find myself saying that either, but the old 35mm AF Mamiya F3.5 (at least the one I have) was darn good, better than I remembered.

Sincerely
Paul
Title: Re: Best ISO for IQ280
Post by: Steve Hendrix on July 10, 2015, 03:21:16 pm
Yunli,
I don't think anyone is really arguing the point that the raw data is the same for ISO 35, 50 and 100. As is so often the case with these debates, it seems to be one about semantics and tact. I happen to be in the BJL camp here. I don't see ISO 35 as a "fake" ISO. I see it as the only ISO that is "real". All the other ones are "fake." Therefore, I think of ISO 35 as the base ISO, and 50/100 (and all the others) as some sort of push. I think this is supported by the DXO graph. It is the ISO standard that leads me to this view. You may choose to look at it differently, which is fine by me. Just please don't bother trying to convince me that your perspective is the only one that is correct.

This is an interesting position for me to take because I've owned an IQ180 since they were first released (ordered Apr-2011 delivered Aug-2011). Some may remember when this back was first announced the base ISO was not 35. It was an early firmware release that provided the option for 35 ISO.

I do not agree with your position that this is some conspiracy on the part of PhaseOne. As Bernard stated, all this isn't rocket science; learn how the camera / back / histogram / metering works and shoot accordingly. I don't see this any differently than the old Velvia debate. Was it really ISO 50, or was it ISO 35 film?? Those who loved the saturated colors used it at 50. Those who wanted a more neutral result used it (carefully) at 35. Was 50 a conspiracy on the part of Fuji? Not to me, but think what you want.

You state your definition of proper exposure is to check with RawDigger. While I understand and appreciate that, as a landscape photographer I find it particularly difficult to do that in the field. What I do is use both ISO 35 and ISO 100. In order to be efficient for me I use ISO 35 when I am worried about shadow detail, and ISO 100 when worried about blowing highlights. I'm sure that sounds ridiculous to you, but that keeps me moving when the light is changing fast. I don't have a light meter in the field at all so I rely on my head and the histogram, which needs to be interpreted (especially my head).

What I find amusing about all this is the two photos below. I took these while backpacking in the Wind Rivers. Although I've posted them in other threads, I think they are useful in getting a point across. The first image was taken at sunset with IQ180/Alpa STC/90hrsw ISO 35. The second image was taken the next morning with Sony a7r/Leica 90 summicron ISO 100. Why did I use the Sony in the morning? Was it because I was worried about the wide dynamic range of this shot? No, it was because it was cold, I was in a hurry and I had a miserable sleepless night because of a nasty headache and buffeting winds against the tent all night. I figured I would drop half of the Alpa gear in my state at the time.

The point is at the end of the day it is the Sony image that has blown highlights and struggles with the dynamic range of the scene. So all of this debate pales in comparison to what subjects you like to shoot and what conditions you have to deal with.

To the OP I would offer this: If you are worried about highlights, use ISO 100. If you are worried about shadows use ISO 35. But most of all, do what gives you the best results given your workflow.

Dave

(http://www.davechewphotography.com/temp_images/windriverpost/DChew_140904_007713_p2-FrameShop.jpg)

(http://www.davechewphotography.com/temp_images/windriverpost/DChew_140905_01800_p1-FrameShop.jpg)

Dave - I think that is really well said. At the end of the day, we're all photographers, or people with cameras in their hands at least, and what you wrote makes total sense and is what matters.

I don't understand why some (yes, Yunli, I'm looking at you) continue to hammer home insignificant points, page after page. Why the war, why the conflict, why the need to make some sort of point of very infinitesimal value and present others as engaging in and extending your conflict? Is it so important to be right on whatever single, non critical point you're trying to make, rather than have some spirit of photography, and of people who are engaged in it and passionate about it? Why not talk about that? Why not come from that perspective - at least once in a while.

I'm not trying to be grouchy - really, I'm not! - I just don't understand this pursuit and I'm asking for a reconsideration of this (and similar) pursuit(s).

Some really good information was brought out by this thread - why not focus on expanding on that as valuable information for the readers rather than driving home pissing match points?

Steve Hendrix
CI
Title: Re: Best ISO for IQ280
Post by: eronald on July 10, 2015, 03:33:21 pm
of course it is the Sony which will blow the highlights at the earliest opportunity if rated normally BECAUSE THE PHASE UNDEREXPOSES BY 1.5 STOPS @ ISO 100 BY DESIGN. It's not rocket science: Overexpose at a standard rating on a dLSR, goodbye data, hello burnout. Overexpose on a Phase back and you have padding, by design, because the ISO is fake. Of course this will then allow Dealer Doug to crow about the better behavior of the back. It is true, they are more foolproof.

Anyway, anyone with a Sony should just shoot the ISO 100 as ISO 400 and enjoy the added highlight protection, with shadows protected by the superior DR.

Edmund

Yunli,
I don't think anyone is really arguing the point that the raw data is the same for ISO 35, 50 and 100. As is so often the case with these debates, it seems to be one about semantics and tact. I happen to be in the BJL camp here. I don't see ISO 35 as a "fake" ISO. I see it as the only ISO that is "real". All the other ones are "fake." Therefore, I think of ISO 35 as the base ISO, and 50/100 (and all the others) as some sort of push. I think this is supported by the DXO graph. It is the ISO standard that leads me to this view. You may choose to look at it differently, which is fine by me. Just please don't bother trying to convince me that your perspective is the only one that is correct.

This is an interesting position for me to take because I've owned an IQ180 since they were first released (ordered Apr-2011 delivered Aug-2011). Some may remember when this back was first announced the base ISO was not 35. It was an early firmware release that provided the option for 35 ISO.

I do not agree with your position that this is some conspiracy on the part of PhaseOne. As Bernard stated, all this isn't rocket science; learn how the camera / back / histogram / metering works and shoot accordingly. I don't see this any differently than the old Velvia debate. Was it really ISO 50, or was it ISO 35 film?? Those who loved the saturated colors used it at 50. Those who wanted a more neutral result used it (carefully) at 35. Was 50 a conspiracy on the part of Fuji? Not to me, but think what you want.

You state your definition of proper exposure is to check with RawDigger. While I understand and appreciate that, as a landscape photographer I find it particularly difficult to do that in the field. What I do is use both ISO 35 and ISO 100. In order to be efficient for me I use ISO 35 when I am worried about shadow detail, and ISO 100 when worried about blowing highlights. I'm sure that sounds ridiculous to you, but that keeps me moving when the light is changing fast. I don't have a light meter in the field at all so I rely on my head and the histogram, which needs to be interpreted (especially my head).

What I find amusing about all this is the two photos below. I took these while backpacking in the Wind Rivers. Although I've posted them in other threads, I think they are useful in getting a point across. The first image was taken at sunset with IQ180/Alpa STC/90hrsw ISO 35. The second image was taken the next morning with Sony a7r/Leica 90 summicron ISO 100. Why did I use the Sony in the morning? Was it because I was worried about the wide dynamic range of this shot? No, it was because it was cold, I was in a hurry and I had a miserable sleepless night because of a nasty headache and buffeting winds against the tent all night. I figured I would drop half of the Alpa gear in my state at the time.

The point is at the end of the day it is the Sony image that has blown highlights and struggles with the dynamic range of the scene. So all of this debate pales in comparison to what subjects you like to shoot and what conditions you have to deal with.

To the OP I would offer this: If you are worried about highlights, use ISO 100. If you are worried about shadows use ISO 35. But most of all, do what gives you the best results given your workflow.

Dave

(http://www.davechewphotography.com/temp_images/windriverpost/DChew_140904_007713_p2-FrameShop.jpg)

(http://www.davechewphotography.com/temp_images/windriverpost/DChew_140905_01800_p1-FrameShop.jpg)
Title: Re: IQ280 and A99 have minimum EI within ISO recommended limits, D810 no
Post by: voidshatter on July 10, 2015, 03:50:10 pm
I skipped any debate about the Sony A99, or whether the IQ180 or A99 can use certain ISO EI settings, but since you ask: I see nothing wrong with the EI=50 on the A99.  What I am reporting on is a guideline on exposure latitude in the ISO 12232 standard that the SSat value is the minimum suggested exposure index setting (based roughly on giving three stops of highlight headroom: placing the metered luminance level at a raw level three stops below maximum.) Since 35>29 and 50>48, both are within that guideline.  It is the Nikon D810 minimum EI of 32 that falls outside it, with 32 being less that its SSat of 47 (as measured by DXO), so that EI setting gives about 1/2 stop less highlight headroom than the ISO suggested minimum.

So you've reached a conclusion that Sony is falsely advertising the native base ISO for the A99? They advertise for 100 but apparently they are deceiving and they should modify it to 50, is this correct?
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 10, 2015, 04:11:51 pm
Yunli,
I don't think anyone is really arguing the point that the raw data is the same for ISO 35, 50 and 100. As is so often the case with these debates, it seems to be one about semantics and tact. I happen to be in the BJL camp here. I don't see ISO 35 as a "fake" ISO. I see it as the only ISO that is "real". All the other ones are "fake." Therefore, I think of ISO 35 as the base ISO, and 50/100 (and all the others) as some sort of push. I think this is supported by the DXO graph. It is the ISO standard that leads me to this view. You may choose to look at it differently, which is fine by me. Just please don't bother trying to convince me that your perspective is the only one that is correct.

This is an interesting position for me to take because I've owned an IQ180 since they were first released (ordered Apr-2011 delivered Aug-2011). Some may remember when this back was first announced the base ISO was not 35. It was an early firmware release that provided the option for 35 ISO.

I do not agree with your position that this is some conspiracy on the part of PhaseOne. As Bernard stated, all this isn't rocket science; learn how the camera / back / histogram / metering works and shoot accordingly. I don't see this any differently than the old Velvia debate. Was it really ISO 50, or was it ISO 35 film?? Those who loved the saturated colors used it at 50. Those who wanted a more neutral result used it (carefully) at 35. Was 50 a conspiracy on the part of Fuji? Not to me, but think what you want.

You state your definition of proper exposure is to check with RawDigger. While I understand and appreciate that, as a landscape photographer I find it particularly difficult to do that in the field. What I do is use both ISO 35 and ISO 100. In order to be efficient for me I use ISO 35 when I am worried about shadow detail, and ISO 100 when worried about blowing highlights. I'm sure that sounds ridiculous to you, but that keeps me moving when the light is changing fast. I don't have a light meter in the field at all so I rely on my head and the histogram, which needs to be interpreted (especially my head).

What I find amusing about all this is the two photos below. I took these while backpacking in the Wind Rivers. Although I've posted them in other threads, I think they are useful in getting a point across. The first image was taken at sunset with IQ180/Alpa STC/90hrsw ISO 35. The second image was taken the next morning with Sony a7r/Leica 90 summicron ISO 100. Why did I use the Sony in the morning? Was it because I was worried about the wide dynamic range of this shot? No, it was because it was cold, I was in a hurry and I had a miserable sleepless night because of a nasty headache and buffeting winds against the tent all night. I figured I would drop half of the Alpa gear in my state at the time.

The point is at the end of the day it is the Sony image that has blown highlights and struggles with the dynamic range of the scene. So all of this debate pales in comparison to what subjects you like to shoot and what conditions you have to deal with.

To the OP I would offer this: If you are worried about highlights, use ISO 100. If you are worried about shadows use ISO 35. But most of all, do what gives you the best results given your workflow.

Dave

(http://www.davechewphotography.com/temp_images/windriverpost/DChew_140904_007713_p2-FrameShop.jpg)

(http://www.davechewphotography.com/temp_images/windriverpost/DChew_140905_01800_p1-FrameShop.jpg)

Nice pictures Dave :) Of course we can stop using the word "fake" but it doesn't change the fact that ISO 35 of IQ180 is essentially the same as ISO 50 on Sony A99, i.e. extended ISO. It is one way or the other as below:

a) The IQ180 is accurately advertised for ISO 35 as base but falsely advertised for anything above ISO 35 (for underexposed images not up to the standard), possibly trying to hide its poor low-light performance;
b) The IQ180 is indeed an ISO 100 camera but is not explicitly specified with ISO 35 as extended ISO, giving the user the false impression that using ISO 35 can gain more DR than using ISO 100, and increasing the self-satisfaction of the user.

I would say that either way Phase One is clever and this is all about marketing. If Phase One follows Canon/Nikon/Sony's specification rules then the IQ180 would either look poor in low-light or look less awesome for the low ISO number.

As for the correct exposure for landscape without tethering, I have already shown by actual experiments that no matter whatever ISO you choose, you won't be able to get accurate highlight clip warning out of IQ260 or Nikon. Actually ISO 50 for IQ260 and ISO 50 for D4S are both best for playback purposes as the highlight clip warnings are most close to RawDigger results. You might end up using the extended ISO settings for Canon/Nikon/Sony for a more accurate playback. The IQ3 series is advertised for the ability to report true histogram for RAW but I haven't tested it yet.

As for your examples, if you shoot the same picture with IQ180 and A7R side by side, both with correct ETTR without bracketing, then the IQ180 would have less recoverable shadow details. However you don't do long exposure shots so I see no problem bracketing and DR will not be of an issue in such scene for the IQ180.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 10, 2015, 04:23:24 pm

Dave - I think that is really well said. At the end of the day, we're all photographers, or people with cameras in their hands at least, and what you wrote makes total sense and is what matters.

I don't understand why some (yes, Yunli, I'm looking at you) continue to hammer home insignificant points, page after page. Why the war, why the conflict, why the need to make some sort of point of very infinitesimal value and present others as engaging in and extending your conflict? Is it so important to be right on whatever single, non critical point you're trying to make, rather than have some spirit of photography, and of people who are engaged in it and passionate about it? Why not talk about that? Why not come from that perspective - at least once in a while.

I'm not trying to be grouchy - really, I'm not! - I just don't understand this pursuit and I'm asking for a reconsideration of this (and similar) pursuit(s).

Some really good information was brought out by this thread - why not focus on expanding on that as valuable information for the readers rather than driving home pissing match points?

Steve Hendrix
CI

Hi Steve, while you find this to be insignificant, I find it crucial to understand all this under the hood for the ultimate image quality, not just superstitions. Dealers tend to advertise ISO 35 for its superiority and users also tend to show superiority out of this. I find these not clearly explained. If I was a dealer I would explain this honestly and clearly how this works so the potential buyer wouldn't be turned down by the IQ3 80MP having only as low as ISO 50.
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 10, 2015, 05:31:08 pm
HI,

I missed out on that. Truth is simply that this is an example of sloppy working. If the photographer checked the histogram and the blinkies it would be obvious that exposures would need to be reduced. Another point is that it is a bit odd to compare a low contrast evening scene with a high contrast morning scene.

One point I see sometimes is that photographers show sloppy work with say Canon and compare with well done work on MFD. I shoot both formats, but both on tripod and with equal care. That may explain in part that my images don't differ a lot.

I check both blinkies and histogram on both Sony and P45+. The histogram gives a good indication of clipping and the blinkies tell me where clipping occurs. By and large, I find these indications quite reliable although on the conservative side. If you have clipped highlights you should learn to use your camera. It may be harsh words, but clipping was always considered a cardinal sin in photography.

That said, Capture One has a tendency to push correctly exposed images into clipping if used with film curve. Lightroom on the other hand applies highlight recovery without telling the user about it.

I wouldn't say that the image below is a very good one:

But it illustrates that a Sony 99 SLT can separate out the disc of the sun through clouds:

While still having good detail in the shadows:

The info from RawDigger is something like this:

This was essentially a snapshot, but I checked the blinkies and saw that sky/clouds were OK except around the sun. I also used the P45+ at that time, but for very different images.

Best regards
Erik

of course it is the Sony which will blow the highlights at the earliest opportunity if rated normally BECAUSE THE PHASE UNDEREXPOSES BY 1.5 STOPS @ ISO 100 BY DESIGN. It's not rocket science: Overexpose at a standard rating on a dLSR, goodbye data, hello burnout. Overexpose on a Phase back and you have padding, by design, because the ISO is fake. Of course this will then allow Dealer Doug to crow about the better behavior of the back. It is true, they are more foolproof.

Anyway, anyone with a Sony should just shoot the ISO 100 as ISO 400 and enjoy the added highlight protection, with shadows protected by the superior DR.

Edmund

Title: Re: Best ISO for IQ280
Post by: dchew on July 10, 2015, 05:56:11 pm
of course it is the Sony which will blow the highlights at the earliest opportunity if rated normally BECAUSE THE PHASE UNDEREXPOSES BY 1.5 STOPS @ ISO 100 BY DESIGN. It's not rocket science: Overexpose at a standard rating on a dLSR, goodbye data, hello burnout. Overexpose on a Phase back and you have padding, by design, because the ISO is fake. Of course this will then allow Dealer Doug to crow about the better behavior of the back. It is true, they are more foolproof.

Anyway, anyone with a Sony should just shoot the ISO 100 as ISO 400 and enjoy the added highlight protection, with shadows protected by the superior DR.

Edmund

I completely agree, and apologize if my original post implied otherwise. I was simply trying to put this "what ISO" question into context.

Although I told myself "only one post", I already broke that rule above, so...

Nice pictures Dave :) Of course we can stop using the word "fake" but it doesn't change the fact that ISO 35 of IQ180 is essentially the same as ISO 50 on Sony A99, i.e. extended ISO. It is one way or the other as below:

a) The IQ180 is accurately advertised for ISO 35 as base but falsely advertised for anything above ISO 35 (for underexposed images not up to the standard), possibly trying to hide its poor low-light performance;
b) The IQ180 is indeed an ISO 100 camera but is not explicitly specified with ISO 35 as extended ISO, giving the user the false impression that using ISO 35 can gain more DR than using ISO 100, and increasing the self-satisfaction of the user.

Thank you. I think the DXO data supports a, not b. But I don't agree with your classification of "falsely advertised", or the motives you state behind either a or b. That part is conjecture and opinion that you are placing on others with no evidence. In my mind those accusations are specifically where you go over the line, and why people's butt-hairs get in a bunch.

Quote
I would say that either way Phase One is clever and this is all about marketing. If Phase One follows Canon/Nikon/Sony's specification rules then the IQ180 would either look poor in low-light or look less awesome for the low ISO number.

Here again, I don't agree with your categorization. And the idea that if they followed some rule from other manufacturers the IQ180 would "look poor in low-light..." is off in the weeds. The IQ180 (or any other camera for that matter) doesn't get its look from a spec compared to another camera. It gets its "look" from a raw file. If Phase One followed the other's specification rules, the files from an IQ180 would look just as darn good as they do now. Not any different. Photographers quickly learn how a tool reacts and then use the tool to get the results they want. You seem to think there are a lot of buyers out there who buy a MF back based on a spec. I know a lot of MF back owners. Everyone I know had some sort of hands-on experience with the actual back or one like it before they bought.

Quote
As for the correct exposure for landscape without tethering, I have already shown by actual experiments that no matter whatever ISO you choose, you won't be able to get accurate highlight clip warning out of IQ260 or Nikon. Actually ISO 50 for IQ260 and ISO 50 for D4S are both best for playback purposes as the highlight clip warnings are most close to RawDigger results. You might end up using the extended ISO settings for Canon/Nikon/Sony for a more accurate playback. The IQ3 series is advertised for the ability to report true histogram for RAW but I haven't tested it yet.

I agree and appreciate all the work you have posted up here and on other forums.

Quote
As for your examples, if you shoot the same picture with IQ180 and A7R side by side, both with correct ETTR without bracketing, then the IQ180 would have less recoverable shadow details. However you don't do long exposure shots so I see no problem bracketing and DR will not be of an issue in such scene for the IQ180.

I completely agree with that.

Dave
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 10, 2015, 06:25:40 pm
But I don't agree with your classification of "falsely advertised", or the motives you state behind either a or b. That part is conjecture and option that you are placing on others with no evidence. In my mind those accusations are specifically where you go over the line, and why people's butt-hairs get in a bunch.

Here again, I don't agree with your categorization. And the idea that if they followed some rule from other manufacturers the IQ180 would "look poor in low-light..." is off in the weeds. The IQ180 (or any other camera for that matter) doesn't get its look from a spec compared to another camera. It gets its "look" from a raw file. If Phase One followed the other's specification rules, the files from an IQ180 would look just as darn good as they do now. Not any different. Photographers quickly learn how a tool reacts and then use the tool to get the results they want. You seem to think there are a lot of buyers out there who buy a MF back based on a spec. I know a lot of MF back owners. Everyone I know had some sort of hands-on experience with the actual back or one like it before they bought.

What I was trying to suggest is that:

If Phase One follows Canon/Nikon/Sony's specification rules, then the specifications for the IQ180 would look like:

ISO 35 - ISO 320 for full resolution, and ISO 50 - ISO 1280 for Sensor+

ISO 35 - ISO 800 for full resolution, and ISO 140 - ISO 3200 for Sensor+

To me the former is definitely a lot less impressive than the latter. These numbers in the specifications play a significant role for marketing. When you do these numbers right and cleverly you gain more potential buyers, and buyers tend to live with the gear they purchase even if they later find its performance under expectations. Actually most users would never find that ISO 800 of the IQ180 is only as bright as ISO 320 of a Canon/Nikon/Sony, so this is good for marketing.

PS: evidence attached.
Title: Re: Best ISO for IQ280
Post by: DucatiTerminator on July 10, 2015, 06:49:53 pm
What I was trying to suggest is that:

If Phase One follows Canon/Nikon/Sony's specification rules, then the specifications for the IQ180 would look like:

ISO 35 - ISO 320 for full resolution, and ISO 50 - ISO 1280 for Sensor+

ISO 35 - ISO 800 for full resolution, and ISO 140 - ISO 3200 for Sensor+

To me the former is definitely a lot less impressive than the latter. These numbers in the specifications play a significant role for marketing. When you do these numbers right and cleverly you gain more potential buyers, and buyers tend to live with the gear they purchase even if they later find its performance under expectations. Actually most users would never find that ISO 800 of the IQ180 is only as bright as ISO 320 of a Canon/Nikon/Sony, so this is good for marketing.

Are you also suggesting that the potential buyer of such a back isn't going to try it out first to see if it meets his/her needs?

Alvin
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 10, 2015, 07:00:06 pm
Are you also suggesting that the potential buyer of such a back isn't going to try it out first to see if it meets his/her needs?

Alvin

What happens most of the time is that a potential buyer books a test drive, brings his own existing gear, briefly does some test shots. With no prior knowledge of the measured ISO (i.e. saturation EI) of each camera, he gets some sample images at the same ISO but are not directly comparable (at least not at the same level for saturation/highlight clipping). When he's home he fails to get a valid comparison but instead draws some weak conclusions such like one has better highlight protection while the other has better shadow recoverability. It is not convenient to book another test drive. He is overwhelmed by the resolution of the digital back at the lowest ISO setting (for which he decides to use in most cases) so he pulls the trigger. After the honey moon he becomes familiar with the real SSat EI of the digital back and he might eventually find that under a fair comparison the digital back may not perform up to expectation.
Title: Re: Best ISO for IQ280
Post by: DucatiTerminator on July 10, 2015, 07:59:45 pm
What happens most of the time is that a potential buyer books a test drive, brings his own existing gear, briefly does some test shots. With no prior knowledge of the measured ISO (i.e. saturation EI) of each camera, he gets some sample images at the same ISO but are not directly comparable (at least not at the same level for saturation/highlight clipping). When he's home he fails to get a valid comparison but instead draws some weak conclusions such like one has better highlight protection while the other has better shadow recoverability. It is not convenient to book another test drive. He is overwhelmed by the resolution of the digital back at the lowest ISO setting (for which he decides to use in most cases) so he pulls the trigger. After the honey moon he becomes familiar with the real SSat EI of the digital back and he might eventually find that under a fair comparison the digital back may not perform up to expectation.

In certain respects, I don't see this as being much different than buying a (rarer) performance car. You can read the literature, poke around forums, and hopefully take one out for a test drive, but in the end, you don't really get to see what it's really like day in and day out until you pull that trigger. The main difference is that you can actually rent an IQx80, and I believe there are several places that will apply that rental charge towards the purchase of the back within a reasonable time frame. Try that with an exotic car, LOL. I come from the motorcycle world, and it's even tougher there, forcing you to rely on tests and the words of others, many of whom don't even ride as well as you do. I 'm happy that it's different with photo hardware/software. I'd like to think that before anyone drops $XX,XXX into a 80MP camera back that he or she is going to base his/her decision on more than just some test shots he takes during a demo. I was recently considering the purchase of a 5DSr. I read a news release for the new P1 camera (on a Canon site of all places) and it intrigued me enough to look into it. I attended a demo for it a few weeks later, knowing well that this was a system that was beyond my capabilities/requirements. Everyone there (with the exception of a D800 guy and myself) had some experience with digital medium format, several with older P1 backs/equipment. I listened attentively to everyone's questions, hoping to learn what I could regarding capabilities and concerns. Interestingly, not once did I hear anyone complain, "Awww shit, I'm not happy with you guys and I don't believe your marketing BS, because the real SSat EI of my IQ180/280 isn't what you claim it to be in your marketing literature." Granted, it's the salespersons' jobs to get me excited about the P1 system, however, all I heard from the attendees (as I asked them for there opinions and insights) was something along the lines of, "try one/rent one/borrow one, you're really going to like it." Same goes for the P1-using members of the forums I've visited. I have yet to hear anyone telling me I won't like it or have buyers' remorse. You see, I am that chump that will be "overwhelmed by the resolution of the digital back at the lowest ISO setting (for which he decides to use in most cases)" and perhaps even P1's easy marketing target, however, not even I will pull that trigger without first doing my due diligence. My$0.02.

Alvin
Title: Re: Best ISO for IQ280
Post by: Steve Hendrix on July 10, 2015, 10:25:26 pm
Hi Steve, while you find this to be insignificant, I find it crucial to understand all this under the hood for the ultimate image quality, not just superstitions. Dealers tend to advertise ISO 35 for its superiority and users also tend to show superiority out of this. I find these not clearly explained. If I was a dealer I would explain this honestly and clearly how this works so the potential buyer wouldn't be turned down by the IQ3 80MP having only as low as ISO 50.

What I find insignificant is the allegation that by listing ISO 35 on their datasheets, Phase One has committed some sort of fraud. Our clients understand that image quality truly begins significant degradation at ISO 200 (which doesn't mean they can't use it) with most digital backs and that they obtain optimal results with ISO 100 and lower. I find some of the information brought out by you and others in this thread regarding the highlight and shadow pulling and pushing to be helpful - and significant. In some instances ISO 35 might be best, in others ISO 100 might be, the focus there I have no problem with.

But I do find it insignificant to go on and on about "deceitfulness, cheating and dishonesty" with regard to a manufacturer offering 35 ISO if the native ISO is 100. I don't really see Phase One marketing ISO 35 as the best ISO choice for quality in their datasheets (it could be in there somewhere, I don't know), but even if they did, they'd hardly be creating an egregious sin. Those using ISO 35 will in many situations be getting the best image quality. And perhaps as has been stated ISO 100 would also result in the best image quality, depending on how they would be shooting a scene. I don't see any big deceit here. And that is the insignificant portion I am describing.

And all manufacturers stretch the high end of their ISO claims, almost everyone who has shot a camera knows that and is aware that even though ISO 128,000 is listed on the data sheet (or in a CCD digital back, ISO 800), it may not be that useful a choice. And anyone who buys a digital back from any responsible dealer has already discussed that before purchasing.

What I do know is that you use terms like dishonest and deceitful and cheating in many of your posts - even in the post above that you wrote to me, implying that there is dishonesty if a dealer emphasizes ISO 35 as a good quality choice to their users. I don't think this is a language issue. You have the potential for a useful message Yunli, if your findings are presented as an opportunity for clarity, but you throw those terms around quite recklessly, my friend.

That's the issue. Take what you know and use it to inform, don't use it to make accusations.

Steve Hendrix
CI
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 11, 2015, 02:35:58 am
Hi,

My take is that vendors take some liberties with ISO-numbers. MFD vendors take more liberty than others. Adding to that, variable ISO may not really exist on some cameras.

I am not very familiar with the ISO standard, but I know that there are at least three different versions. Two are really based on JPEG the third one is based on pixel saturation.

Saturation based ISO seems most relevant for any camera used with RAW. The official ISO documents are quite expensive, a short description is given here:

Wikipedia says:
Quote
The saturation-based speed is defined as

S_{\mathrm{sat}} = \frac{78\;\text{lx⋅s}}{H_{\mathrm{sat}}},
where H_{\mathrm{sat}} is the maximum possible exposure that does not lead to a clipped or bloomed camera output. Typically, the lower limit of the saturation speed is determined by the sensor itself, but with the gain of the amplifier between the sensor and the analog-to-digital converter, the saturation speed can be increased. The factor 78 is chosen such that exposure settings based on a standard light meter and an 18-percent reflective surface will result in an image with a grey level of 18%/√2 = 12.7% of saturation. The factor √2 indicates that there is half a stop of headroom to deal with specular reflections that would appear brighter than a 100% reflecting white surface.[58]

So an 18% grey card should be exposed at 12.7% saturation, that is 2.8 EV below saturation.

If we assume that we have no variable amplification between sensor output and also no manipulation on the raw file, we end up with a single ISO rating. That is base ISO. So, now, how is variable ISO achieved?

• A good strategy may be to not change anything. Just put a tag in the raw file indicating the intended ISO. Raw file still contains all data. The raw processor can use ISO tag for optimal processing. Phase One uses this strategy between 35ISO and 100 ISO on the IQ-180.
• Another strategy is to multiply the values in the raw file with an ISO depending value. That is what Phase One seems doing on the IQ-180 above 100 ISO. This is essentially the same as throwing away highlight protection.
• At 1600 ISO IQ 180 can kick in Sensor+ pixel binning, which improves DR a bit.

My take is simply:

Base ISO is around 35.

Using the sensor between 35 and 100 ISO does make little difference as long as optimal exposure is applied.  Above 100 ISO and 1600 ISO the raw file is affected and just throwing away highlight protection.

Sensor plus kicks in at 1600 ISO.

So, I would not use the ISO range between 100 ISO and 1600 ISO, just reduce exposure. That would keep my specular highlights intact. Now, the raw processor could use the ISO tag for better looking images by optimising processing.

Best regards
Erik

What I find insignificant is the allegation that by listing ISO 35 on their datasheets, Phase One has committed some sort of fraud. Our clients understand that image quality truly begins significant degradation at ISO 200 (which doesn't mean they can't use it) with most digital backs and that they obtain optimal results with ISO 100 and lower. I find some of the information brought out by you and others in this thread regarding the highlight and shadow pulling and pushing to be helpful - and significant. In some instances ISO 35 might be best, in others ISO 100 might be, the focus there I have no problem with.

But I do find it insignificant to go on and on about "deceitfulness, cheating and dishonesty" with regard to a manufacturer offering 35 ISO if the native ISO is 100. I don't really see Phase One marketing ISO 35 as the best ISO choice for quality in their datasheets (it could be in there somewhere, I don't know), but even if they did, they'd hardly be creating an egregious sin. Those using ISO 35 will in many situations be getting the best image quality. And perhaps as has been stated ISO 100 would also result in the best image quality, depending on how they would be shooting a scene. I don't see any big deceit here. And that is the insignificant portion I am describing.

And all manufacturers stretch the high end of their ISO claims, almost everyone who has shot a camera knows that and is aware that even though ISO 128,000 is listed on the data sheet (or in a CCD digital back, ISO 800), it may not be that useful a choice. And anyone who buys a digital back from any responsible dealer has already discussed that before purchasing.

What I do know is that you use terms like dishonest and deceitful and cheating in many of your posts - even in the post above that you wrote to me, implying that there is dishonesty if a dealer emphasizes ISO 35 as a good quality choice to their users. I don't think this is a language issue. You have the potential for a useful message Yunli, if your findings are presented as an opportunity for clarity, but you throw those terms around quite recklessly, my friend.

That's the issue. Take what you know and use it to inform, don't use it to make accusations.

Steve Hendrix
CI
Title: Re: Best ISO for IQ280
Post by: Chris Livsey on July 11, 2015, 03:49:42 am

If the photographer checked the histogram and the blinkies it would be obvious that exposures would need to be reduced.

Best regards
Erik

Regrettably the "blinkies" are not set (and I am aware a variable setting is available on more recent backs) so that this is an entirely useful way of working. Not only do the "blinkies" on the back not match those on import (to C1) the C1 version varies depending on the curve set and the ICC profile selected.
I never got an answer that was unequivocal from Phase One on how much "protection" I had on my P20 AFTER the "blinkies" kicked in. No doubt because so many processing parameters are intertwined.
"Blinkies" on the back, flashing as if to warn of a nuclear strike, on import with adjustments which are not end of slider produce an image that is "normal".
As base 35iso provides headroom so do the blinkies. To shoot expose to the right needs courage and faith, should that be the case?
I understand the "blinkies" on the back are not reflective of the RAW due mainly to processing restraints and I assume the histogram is the same so I do not concur with your statement: exposure would need to be reduced . Of course that these indicators of exposure are incorrect is another clear case of makers and especially dealers showing  "deceitfulness, cheating and dishonesty"   ;). Certainly not the photographers not actually understanding what is going on in the camera and the software.
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 11, 2015, 04:45:48 am
Hi,

The P45+ I have has blinkies and they provide very little headroom. C1 used with the standard "film" curve  overexposes the highlights. The linear setting gives a more correct rendition. C1 histograms are simply not a good representation of the raw data. Lightroom processing pipeline 2012 is even more misleading as it always applies highlight recovery.

Checking out the raw data with a good tool like RawDigger is helpful  in learning the workings of the camera and raw conversion.

The enclosed images are from my most recent shots with the P45+ (*)

Two images show the raw data. My recollection is that the blinkies indicated clipping in the area that was actually clipped.

Next is the image imported in Capture One at defaults setting, note that it indicates clipping on a much larger area.

The last one is a processed variant in LR6.

Best regards
Erik

(*) I had another shot with the P45+, but no CF-card -- no images :-(

Regrettably the "blinkies" are not set (and I am aware a variable setting is available on more recent backs) so that this is an entirely useful way of working. Not only do the "blinkies" on the back not match those on import (to C1) the C1 version varies depending on the curve set and the ICC profile selected.
I never got an answer that was unequivocal from Phase One on how much "protection" I had on my P20 AFTER the "blinkies" kicked in. No doubt because so many processing parameters are intertwined.
"Blinkies" on the back, flashing as if to warn of a nuclear strike, on import with adjustments which are not end of slider produce an image that is "normal".
As base 35iso provides headroom so do the blinkies. To shoot expose to the right needs courage and faith, should that be the case?
I understand the "blinkies" on the back are not reflective of the RAW due mainly to processing restraints and I assume the histogram is the same so I do not concur with your statement: exposure would need to be reduced . Of course that these indicators of exposure are incorrect is another clear case of makers and especially dealers showing   "deceitfulness, cheating and dishonesty"  ;). Certainly not the photographers not actually understanding what is going on in the camera and the software.
Title: Re: Best ISO for IQ280
Post by: Chris Livsey on July 11, 2015, 06:08:38 am
Erik

As usual thank you for your detailed response, always interesting and appreciated.
I am at the early stages of investigating my P45+ responses but a rough and ready headroom test, using a grey card progressively over exposed in half stop increments showed a "white out" on the back blinkies which was fully recovered by exposure adjustment in C1 and also partly separately by a linear curve applied. I will repeat under more controlled conditions but a stop and a half was recoverable. This is on a uniform area and point highlights are indeed more difficult. If I relied on the blinkie I would be sacrificing available headroom. (This was shooting at 50 iso  ;D )
PS all my best shots are on virtual CF cards !!

Title: Re: Best ISO for IQ280
Post by: eronald on July 11, 2015, 06:24:00 am
The Raw converter has channel recovery techniques too, making the issue of overexposure yet more opaque.
And there is also often some nonlinearity when you get very close to the full well, I believe.
This game is no use to anyone who doesn't live in a lab, and take images exclusively in a lab.

Phase backs specs were cleverly written by salesmen and marketers who understand that "real" photographers live in the real world with pro flash, and it gets very easy to overexpose a highlight eg. a forehead by a stop or so. And who also understand that cameras are often bought on specs. As a result, the customer is getting good -in fact session-saving behaviour - based on a deceptive spec, and Phase is getting customers based on this spec (who here apart from some experts would buy an ISO 35 fixed-ISO back)?

Let's accept that it is easier to agree on a weight or length than on a camera ISO, and let's simply agree whose numbers eg. DxO's we will use. Using Doug's numbers doesn't make more sense than Sony's or Canon's - no disrespect intended to Sony, Canon or Doug of course, the latter's honesty in his business dealings is as legendary as his puffery :P

In all fairness, this game quite possibly originated with Imacon or even Kodak, as all back manufacturers seem to agree to rate their backs identically. Kodak certainly knew what a film speed standard meant.

Edmund

PS. From Wikipedia: In law, puffery is a promotional statement or claim that expresses subjective rather than objective views, which no "reasonable person" would take literally.

Erik

As usual thank you for your detailed response, always interesting and appreciated.
I am at the early stages of investigating my P45+ responses but a rough and ready headroom test, using a grey card progressively over exposed in half stop increments showed a "white out" on the back blinkies which was fully recovered by exposure adjustment in C1 and also partly separately by a linear curve applied. I will repeat under more controlled conditions but a stop and a half was recoverable. This is on a uniform area and point highlights are indeed more difficult. If I relied on the blinkie I would be sacrificing available headroom. (This was shooting at 50 iso  ;D )
PS all my best shots are on virtual CF cards !!

Title: Re: IQ280 and A99 have minimum EI within ISO recommended limits, D810 no
Post by: BJL on July 11, 2015, 07:15:53 am
So you've reached a conclusion that Sony is falsely advertising the native base ISO for the A99? They advertise for 100 but apparently they are deceiving and they should modify it to 50, is this correct?
Does Sony state somewhere that "the A99 has a "native base ISO speed of 100"?  If so, can you give me a link the what Sony says?  Because I am not interested in deciding whether someone is lying until I have the facts, including reading or hearing directly what that person said.
Title: Re: IQ280 and A99 have minimum EI within ISO recommended limits, D810 no
Post by: voidshatter on July 11, 2015, 07:21:43 am
Does Sony state somewhere that "the A99 has a "native base ISO speed of 100"?  If so, can you give me a link the what Sony says?  Because I am not interested in deciding whether someone is lying until I have the facts, including reading or hearing directly what that person said.

The link is displayed in the screenshot of A99's official specification saying "native base ISO speed of 100".
Title: Re: Best ISO for IQ280
Post by: Ken R on July 11, 2015, 07:49:40 am
What I was trying to suggest is that:

If Phase One follows Canon/Nikon/Sony's specification rules, then the specifications for the IQ180 would look like:

ISO 35 - ISO 320 for full resolution, and ISO 50 - ISO 1280 for Sensor+

ISO 35 - ISO 800 for full resolution, and ISO 140 - ISO 3200 for Sensor+

To me the former is definitely a lot less impressive than the latter. These numbers in the specifications play a significant role for marketing. When you do these numbers right and cleverly you gain more potential buyers, and buyers tend to live with the gear they purchase even if they later find its performance under expectations. Actually most users would never find that ISO 800 of the IQ180 is only as bright as ISO 320 of a Canon/Nikon/Sony, so this is good for marketing.

PS: evidence attached.

The Dynamic Range DXo Graph you posted is WRONG. In the Graph you posted it shows a max DR of just under 12 stops for the IQ180. (don't know where you got that?) Here is the right one right off DXo site:

Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 11, 2015, 07:52:18 am
Hi Chris,

You are right on recoverable highlights.

Your feedback is much appreciated, thanks a lot. I wish you a lot of happiness with your P45+ back

Best regards
Erik

Erik

As usual thank you for your detailed response, always interesting and appreciated.
I am at the early stages of investigating my P45+ responses but a rough and ready headroom test, using a grey card progressively over exposed in half stop increments showed a "white out" on the back blinkies which was fully recovered by exposure adjustment in C1 and also partly separately by a linear curve applied. I will repeat under more controlled conditions but a stop and a half was recoverable. This is on a uniform area and point highlights are indeed more difficult. If I relied on the blinkie I would be sacrificing available headroom. (This was shooting at 50 iso  ;D )
PS all my best shots are on virtual CF cards !!

Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 11, 2015, 08:11:34 am
Hi Ken,

You are both right… or false.

DxO presents two kind of diagrams one is normalised to a small print size, like A4, that is the one that you show. The other one is unnormalised and shows per pixel performance.

Both diagrams are valid. For instance, if you would compare unnormalised DxO data with spec sheet coming from Dalsa you would find a very good match. But, a pixel-wise comparison ignores the number of pixels. The normalisation that DxO does takes the number of pixels into account.

As you see, the effect of Sensor+ is very significant on the "per pixel (Screen)" graph but far less pronounced on the "normalised (print)" graph.

I would say both diagrams are valid, but there is good reason DxO does this normalisation.

Another small point may be that we often show images on screen, but most screens today are just two MP, 4K is eight MP. DxO-s normalisation would be decent for a 4K display. For full image resolution we need to print, but prints struggle to even reach a DR of 7EV.

Best regards
Erik

The Dynamic Range DXo Graph you posted is WRONG. Here is the right one right off DXo site:

Title: Re: Best ISO for IQ280
Post by: BJL on July 11, 2015, 10:11:08 am
of course it is the Sony which will blow the highlights at the earliest opportunity if rated normally BECAUSE THE PHASE UNDEREXPOSES BY 1.5 STOPS @ ISO 100 BY DESIGN. ... Overexpose on a Phase back and you have padding, by design, because the ISO is fake.

From persistent falsehoods like this about underexposure and fake ISO values, it seems that some people still do not understand that "ISO" means at least three different things according to the ISO:12232 standard for Photography -- Digital still cameras -- Determination of exposure index, ISO speed ratings, standard output sensitivity, and recommended exposure index, and in particular that the role of a camera's ISO setting in determining the exposure index is unrelated to any measure of a sensor's sensitivity, and cannot be judged at all from the highlight-handling measurement SSat that DXO misleadingly and somewhat arrogantly calls "true ISO speed".

A) "ISO" refers to several quite different quantities defined in the relevant standard ISO:12232 and people who wish to make accusations against camera makers of fake "ISO" values should at least learn the differences.

1) Exposure index, a measure of exposure levels as used by light meters, even off-camera ones, and unrelated to the performance of a particular sensor, but used as units of measure for the others.

2) A speed rating for Sensitivity in the sense of ability to detect light, judged by signal-to-noise ratios and shadow handling. The main standard is S40:1, corresponding to the exposure index at which exposing a uniformly lit subject gives a SNR of 40:1.  (Aside: ISO:12232 specifies that usually, this 40:1 standard should be used to describe the sensitivity of a camera -- but I do not see that done very much!  For Modern CMOS ILCs, this is probably about 800 or higher, regardless of the "ISO" setting on the camera.)

3) Another speed rating for Saturation-based speed Ssat: roughly the exposure level (EI) at which metering based on a certain subject luminance level cases highlights to be blown on the sensor (or clipped in subsequent amplification en route to raw files) at three stops brighter.
This is offered as a measure of the lower end of the camera's exposure latitude; a minimum safe exposure index. It is also the basis for what DXO cals "true ISO speed".

4) Output Sensitivity, relevant only to final JPEG output: level placement in default in-camera JPEGs.

B) The "ISO" dial sets the Exposure Index used by the in-camera light meter (1 above) and controls default JPEG conversion (4 above), and is controlled by the ISO and Japanese CIPA standards for Standard Output Sensitivity and such.  ISO:12232 and the related CIPA standard have absolutely nothing to say how numerical levels are used in raw files, leaving that intermediate step entirely to the implementation decisions of camera makers.

C) DXO also does some testing of EI settings, but does not spend much space reporting them, perhaps because the results are rather boring. DXO concludes that on item (1) most cameras are fairly close to the ISO specification for EI: with the same f-stop, same level of uniform test subject lighting, and the same "ISO" setting, cameras will generally choose roughly the same exposure time.  (Actually DXO skips the lens and f-stop by shining light on the bare sensor and compares the shutter speeds chosen at the cameras' various ISO settings, in order to calibrate its shutter speed choices in subsequent measurements, and observes that in general, they are close to the ISO's definition of Exposure Index.  So no cheating or fakery there!)

So no camera is underexposing the sensor by 1.5 stops, or giving it 1.5 stops less exposure than some other camera, or 1.5 stops less than some ISO prescription for exposure levels.

D) The DXO also measures a version of (2), Saturation-based sensitivity SSat, which in particular is totally unrelated to (1); confusingly, DXO cals this "true ISO speed".  As a perverse example of how this measurement could be misleading, changing nothing in a camera except padding raw levels from a 14-bit ADC to 16 bits by adding leading zeros rather than reporting the original 14-bit values will reduce the SSat and "DXO ISO" by a factor of four, but clearly is not reducing exposure level by two stops.  This is not entirely hypothetical, given that Phase One does so kind of 14->16 conversion whereas most camera makers do not, so if its values are 1.5 stop further below the top of its 16-bit range than some other camera, the actual numerical levels are higher by about 1/2 stop, so a factor of 1.4 larger.

In summary, all I can see that Phase One is doing giving more highlight-protecting headroom than the ISO recommend minimum, while still using somewhat higher numerical raw levels than most or all cameras due to its greater raw file bit depth.
Title: Re: Best ISO for IQ280
Post by: sbernthal on July 11, 2015, 10:47:52 am
I don't have the 180, (have shot it 5 or 6 times), but instead have the 260.  That back is base iso of 50.

So if I follow the information on this thread, it sound like the best overall iso setting on the 260 for highlight control would be iso 100 instead of 50.  50 might give a bit better shadow recovery, but 100 is going to give the best overall exposure?

I think this is the simple answer to the question.
I see no point in the technical talk and graphs.
If you have an IQX80, then perhaps the best all-around ISO for you is 50, to take care of both highlights and shadows.

Is it better to have a back that can do 35 - of course yes.
It gives you more stops of flexibility when you are balancing your exposure.
I've never heard Phase say that a back with ISO 35 has any magical IQ advantage.
Title: Re: Best ISO for IQ280
Post by: chrismuc on July 11, 2015, 11:07:38 am
I made four test shot with my IQ180.

ISO 035 - 4 seconds
ISO 050 - 4 seconds
ISO 100 - 4 seconds
ISO 200 - 4 seconds

All same aperture. Stupid indoor shot (it's night in China) with not too big dynamic range.
I open the four pictures in raw digger and get 4 times exactly the same histogram (see enclosed)!

Now you guys tell what that means?
Does it mean the back works at ISO 35 at any ISO setting?

I don't see highlight clipping but maybe my motive had too little DR and I exposed not too bright.

Another thing I don't understand is: If I open all pictures in ACR, I have to apply the following exposure adjustments to achieve the +/- same exposure and histogram:

035 ISO: reference
050 ISO: -0,5 stops (ok)
100 ISO: -1,5 stops (ok)
200 ISO: -1,5 stops (not 2,5 stops like the ISO difference would suggest)

??

And: After adjusting the exposure, the grain in brighter or darker grey values is the same in all pictures, the ISO 200 picture is not more grainy than the ISO 35 picture.

Tell me if I should upload the raw pictures for your examination.

(Or maybe I do new ones with wider DR.)
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 11, 2015, 02:46:51 pm
I made four test shot with my IQ180.

ISO 035 - 4 seconds
ISO 050 - 4 seconds
ISO 100 - 4 seconds
ISO 200 - 4 seconds

All same aperture. Stupid indoor shot (it's night in China) with not too big dynamic range.
I open the four pictures in raw digger and get 4 times exactly the same histogram (see enclosed)!

Now you guys tell what that means?
Does it mean the back works at ISO 35 at any ISO setting?

I don't see highlight clipping but maybe my motive had too little DR and I exposed not too bright.

Another thing I don't understand is: If I open all pictures in ACR, I have to apply the following exposure adjustments to achieve the +/- same exposure and histogram:

035 ISO: reference
050 ISO: -0,5 stops (ok)
100 ISO: -1,5 stops (ok)
200 ISO: -1,5 stops (not 2,5 stops like the ISO difference would suggest)

??

And: After adjusting the exposure, the grain in brighter or darker grey values is the same in all pictures, the ISO 200 picture is not more grainy than the ISO 35 picture.

Tell me if I should upload the raw pictures for your examination.

(Or maybe I do new ones with wider DR.)

This is interesting. At least for my IQ260 (firmware pre-june-2014) the histogram starts to get more clipping for highlight ever since ISO 200 and higher (which is consistent with dxomark). For your case your IQ180 seems to behave with no additional highlight clipping even for ISO 200, which is against dxomark/sensorgen. What's the date of release of your firmware? Perhaps if you are running the latest firmware then Phase One has changed the implementation and made the back truly ISO-less to avoid any additional highlight clipping beyond ISO 100?
Title: Re: Best ISO for IQ280
Post by: dchew on July 11, 2015, 03:08:21 pm
I will check mine. Can't remember the last time I shot it above 100.
;)

Dave
Title: Re: Best ISO for IQ280
Post by: dchew on July 11, 2015, 03:52:17 pm
Mine matches chrismuc

FW 5.14.29.

Note that I am on a technical camera with a not-exactly-accurate Copal shutter.

(http://www.davechewphotography.com/temp_images/isotest/ISO035-Full-10328x7760.png)

(http://www.davechewphotography.com/temp_images/isotest/ISO050-Full-10328x7760.png)

(http://www.davechewphotography.com/temp_images/isotest/ISO100-Full-10328x7760.png)

(http://www.davechewphotography.com/temp_images/isotest/ISO200-Full-10328x7760.png)

(http://www.davechewphotography.com/temp_images/isotest/ISO400-Full-10328x7760.png)

(http://www.davechewphotography.com/temp_images/isotest/ISO800-Full-10328x7760.png)

Edited to fix normalize scaling in each graph
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 11, 2015, 04:00:30 pm
Dave, could you upload larger screenshots? I could barely see the x-axis!
Title: Re: Best ISO for IQ280
Post by: Ken R on July 11, 2015, 04:26:33 pm
Hi Ken,

You are both right… or false.

DxO presents two kind of diagrams one is normalised to a small print size, like A4, that is the one that you show. The other one is unnormalised and shows per pixel performance.

Both diagrams are valid. For instance, if you would compare unnormalised DxO data with spec sheet coming from Dalsa you would find a very good match. But, a pixel-wise comparison ignores the number of pixels. The normalisation that DxO does takes the number of pixels into account.

As you see, the effect of Sensor+ is very significant on the "per pixel (Screen)" graph but far less pronounced on the "normalised (print)" graph.

I would say both diagrams are valid, but there is good reason DxO does this normalisation.

Another small point may be that we often show images on screen, but most screens today are just two MP, 4K is eight MP. DxO-s normalisation would be decent for a 4K display. For full image resolution we need to print, but prints struggle to even reach a DR of 7EV.

Best regards
Erik

Ok.

So given equal print (or display) size one is always going to be downsizing less (or uprezing less) the IQ180 file vs the Nikon D810 file given the large difference in pixel count.
Title: Re: Best ISO for IQ280
Post by: dchew on July 11, 2015, 04:30:43 pm
Dave, could you upload larger screenshots? I could barely see the x-axis!

Don't tell me you need more resolution!! Hehehe.

I modified the post with individual png's.

Dave
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 11, 2015, 04:32:43 pm
Ok.

So given equal print (or display) size one is always going to be downsizing less (or uprezing less) the IQ180 file vs the Nikon D810 file given the large difference in pixel count.

When you downsample an IQ180 file to the same pixel count as of D810 you gain ln((80/36)^.5)/ln(2) = 0.576 EV increase of DR for the IQ180 thanks to the increase of SNR.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 11, 2015, 04:34:36 pm
Don't tell me you need more resolution!! Hehehe.

I modified the post with individual png's.

Dave

Thanks! Your screenshots look right. If you force the same range of x-axis for every plot then you should see the same exposure and contrast for ISO 35, 50, 100 and 200, but anything beyond 200 would start to clip more highlight. Your results are the same as chrismuc's - all settings <= ISO 200 are the same, and additional clipping of highlight starts from ISO 400.

The turning point at which the additional clipping of highlight starts is different from what dxomark observes (and also different from my IQ260). Perhaps Phase One made a change with the firmware. Do you know the date of release of your firmware?
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 11, 2015, 04:51:43 pm
Looking back to my IQ280 shots (firmware pre-june-2014) I had identical exposure between ISO 35 and ISO 100, though I did not test anything beyond ISO 100.
Title: Re: Best ISO for IQ280
Post by: dchew on July 11, 2015, 05:04:52 pm
Perhaps Phase One made a change with the firmware. Do you know the date of release of your firmware?

4 Nov 2014.
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 11, 2015, 05:05:18 pm
Hi,

The "print" setting i DxO-mark is compensating for pixel sizes, and I feel that is the right approach. Note that it happens to be default in DxO-mark.

Best regards
Erik

Ok.

So given equal print (or display) size one is always going to be downsizing less (or uprezing less) the IQ180 file vs the Nikon D810 file given the large difference in pixel count.
Title: Re: Best ISO for IQ280
Post by: eronald on July 11, 2015, 07:59:31 pm
BJL,

Us dumb guys we look at the Raws, and then our mind boggles, because basically one can set any ISO one wants and measurebate away, the camera doesn't care (http://forum.luminous-landscape.com/index.php?topic=101758.msg836372#msg836372).

So ok, I shouldn't have talked about "fake" ISO, I should have called the 100 setting a "fictitious ISO" because they're all fictitious. But then isn't "reality" just a shared fiction?  Anyway, I'd still call ISO 35 here the "native" ISO but I'm not really sure why any more. Your criticism of my careless wording is probably justified anyway, I am getting dumb and superficial.

I'll give your post a careful reading when I have time, I promise, you put great effort into it and deserve a careful reading. I'm caught up in a hack and can't spare the concentration.

BTW, if you have an up to date version of the ISO:12232 standard or draft of same, could you email it to me please? edmundronald at gmail dot com.

Edmund

From persistent falsehoods like this about underexposure and fake ISO values, it seems that some people still do not understand that

---snip---

In summary, all I can see that Phase One is doing giving more highlight-protecting headroom than the ISO recommend minimum, while still using somewhat higher numerical raw levels than most or all cameras due to its greater raw file bit depth.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 12, 2015, 12:00:50 am
As of firmware v1.05.1 (Jan 2015) the IQ250 only starts to clip more highlight from ISO 400, i.e. ISO 100 and ISO 200 are the same.

Claff PDR (http://home.comcast.net/~NikonD70/Charts/PDR.htm) attached below (note that the x-axis is manufacturer's claimed ISO, not measured ISO)
Title: Re: Best ISO for IQ280
Post by: Ken R on July 12, 2015, 12:39:17 am
As of firmware v1.05.1 (Jan 2015) the IQ250 only starts to clip more highlight from ISO 400, i.e. ISO 100 and ISO 200 are the same.

Claff PDR (http://home.comcast.net/~NikonD70/Charts/PDR.htm) attached below (note that the x-axis is manufacturer's claimed ISO, not measured ISO)

So the PhaseOne IQ250 is significantly better than the 645z?
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 12, 2015, 01:29:26 am
Hi,

Interesting to note that the DPR curve of the IQ-250 differs so much from the Pentax 645Z, as bot use exactly the same sensor. As a hint, BClaff indicates that the ISO-s on the X-axis are rated and not measured. So my guess is that ISO on the IQ-250 is a bit like IQ-180 and on the P645+ it is in accordance with the saturation based ISO standard.

Best regards
Erik

As of firmware v1.05.1 (Jan 2015) the IQ250 only starts to clip more highlight from ISO 400, i.e. ISO 100 and ISO 200 are the same.

Claff PDR (http://home.comcast.net/~NikonD70/Charts/PDR.htm) attached below (note that the x-axis is manufacturer's claimed ISO, not measured ISO)
Title: A99 has minimum EI one stop above ISO recommended minimum
Post by: BJL on July 12, 2015, 02:51:27 am
So you've reached a conclusion that Sony is falsely advertising the native base ISO for the A99? They advertise for 100 but apparently they are deceiving and they should modify it to 50, is this correct?
I see what you are referring to now: the Sony A99 offers exposure index settings ranging from 100 up, whereas (if I am reading DXO's results correctly) the ISO SSat recommendation for the MINIMUM safe exposure index of the sensor is about 48. So Sony is giving four stops of highlight headroom above the midtones placement when auto-exposure is used instead of the three stops suggested as the bare minimum by the ISO standard with its SSat measure.

So I see nothing "false" and no "deception" there, just a perfectly reasonable and allowable design decision to offer more than the bare minimum highlight headroom on a sensor that has plenty of dynamic range to spare.

To repeat yet again: the ISO SSat is intended as a bare minimum Ei (maximum advisable among of exposure to the sensor) not an ideal exposure placement!

Aside. There is an irony here: one common if misguided criticism of digital cameras is that they have more problems with blown highlights (while handling shadows far better.)  But when a camera maker sets AE in a way to improve highlight handling (while still having far better shadow handling than film), some people criticize this as deception or fakery.
Title: Re: Best ISO for IQ280
Post by: BJL on July 12, 2015, 03:06:51 am
So ok, I shouldn't have talked about "fake" ISO, I should have called the 100 setting a "fictitious ISO" because they're all fictitious.
So long as we thing of "ISO" meaning what it meant for film, yes the ISO settings on camera and the ISO SSat (aka "DXO ISO") are all fictitious; the measure completely different things.  ISO:12232 recommend using the noise-based S40:1 measure as the "ISO sensitivity" but for whatever reason I have not seen any camera maker do that!   It might be the case that when some cameras have "low" and "high" ISO exposure index setting outside the normal EI setting range, the former are ones low SSat and the latter are ones above some noise-based threshold like S40:1 or S10:1.

BTW, if you have an up to date version of the ISO:12232 standard or draft of same, could you email it to me please? edmundronald at gmail dot com.
Unfortunately not, since the ISO charges way too much for it.  I have gathered multiple summaries from other sources (starting with the Wikipedia article that I often cite).  I do have a link to the Japanese CIPA DC-004 standard that specifies how "ISO" settings on cameras must be calibrated, at least on Japanese cameras: it's at this page: http://www.cipa.jp/std/std-sec/std-list_e.html
This originated the "Standout Output Sensitivity" part added in the 2006 revision of ISO 12232, and gives some rationale for that addition.
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 12, 2015, 03:26:52 am
So the PhaseOne IQ250 is significantly better than the 645z?

Of course no. The IQ250 is exactly the same as the 645Z. It's just Phase One's "clever wrap" to make the plot "look better". If Phase One follows Canon/Nikon/Sony rules then the IQ250 would overlap with the 645Z and the IQ260 would "look worse".

But of course it's good to know that I don't need to shoot the IQ250 at ISO higher than 200 if I don't need to check focus/composition via playback - digital amplification wouldn't squeeze any more DR out of a Sony CMOS (in contrast with a Canon CMOS with 500nm fab process (https://www.chipworks.com/about-chipworks/overview/blog/full-frame-dslr-cameras-part-ii-canon-stays-course) and external ADC presumably made in China (http://www.lensrentals.com/blog/2015/06/canon-5ds-teardown)).
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 12, 2015, 03:29:44 am
Hi,

Both cameras use the same sensor.

Please note the statemnet: (note that the x-axis is manufacturer's claimed ISO, not measured ISO)

The IQ-250 is probably overrating ISO like the IQ-180 discussed before. As discussed before, this can be seen as a way of protecting highlights.

Best regards
Erik

So the PhaseOne IQ250 is significantly better than the 645z?
Title: Once again: the SSat minimum recommended EI is meaningless to ISO settings!
Post by: BJL on July 12, 2015, 04:43:55 am
As a hint, BClaff indicates that the ISO-s on the X-axis are rated and not measured. So my guess is that ISO on the IQ-250 is a bit like IQ-180 and on the P645+ it is in accordance with the saturation based ISO standard.

Erik, since you are an engineer, I suggest that you would benefit from learning about the ISO:12232(2006) standard and the related CIPA DC-004 standard, because you persist in the total misunderstanding of what ISO SSat measures and what it is not.  For one thing, it is almost completely unrelated to the function of a cameras's "ISO" settings!

DXO measures this, and sees some small variation in the actual exposure index (exposure level suggested by the camera's meter) at a given ISO setting from the EI specified in that ISO setting, but only a little, and not anything close to going all the way down to the SSat minimum EI level.  It is extremely unlikely that Pentax or any camera maker uses that ISO SSat measure of the lower extremity of a camera's exposure latitude to calibrate its ISO exposure index settings, for reasons that I have explained (with references) multiple times in this thread and elsewhere.

For one thing, a camera's "ISO" setting is only relevant to (a) light metering and auto-exposure modes [exposure index], and (b) sensitivity as manifested in the default final JPEG output.  So it has nothing to do with the intermediate processes such as how much gain ("raw levels per photon") is used in producing the raw file data: ISO and CIPA are completely silent on how a camera maker handles the intermediate steps between photo-site signal and JPEG levels.  The extreme of applying equal gain at all ISO settings (or at all settings from 200 up, or all from 400 up) and then scaling up appropriately in the raw-to-JPEG conversion is as consistent with the ISO and CIPA standards as always applying gain in direct proportion to the ISO setting, so that the same raw-to-jpeg mapping is used at all ISO settings.

Further, it would be a total engineering fail to handle high ISO settings with a Sony CMOS sensor with amplification that places the midtones at that SSat based bare minimum of three stops below the maximum raw level: that would risk clipping some highlights that the sensor itself handled fine, and would amplify noise up to far above the raw level spacing, so adding multiple useless bits of noise to the raw levels, and not gaining any noise handling advantage over using less gain.
Title: Re: Once again: the SSat minimum recommended EI is meaningless to ISO settings!
Post by: bjanes on July 12, 2015, 09:24:57 am
Erik, since you are an engineer, I suggest that you would benefit from learning about the ISO:12232(2006) standard and the related CIPA DC-004 standard, because you persist in the total misunderstanding of what ISO SSat measures and what it is not.  For one thing, it is almost completely unrelated to the function of a cameras's "ISO" settings!

DXO measures this, and sees some small variation in the actual exposure index (exposure level suggested by the camera's meter) at a given ISO setting from the EI specified in that ISO setting, but only a little, and not anything close to going all the way down to the SSat minimum EI level.  It is extremely unlikely that Pentax or any camera maker uses that ISO SSat measure of the lower extremity of a camera's exposure latitude to calibrate its ISO exposure index settings, for reasons that I have explained (with references) multiple times in this thread and elsewhere.

For one thing, a camera's "ISO" setting is only relevant to (a) light metering and auto-exposure modes [exposure index], and (b) sensitivity as manifested in the default final JPEG output.  So it has nothing to do with the intermediate processes such as how much gain ("raw levels per photon") is used in producing the raw file data: ISO and CIPA are completely silent on how a camera maker handles the intermediate steps between photo-site signal and JPEG levels.  The extreme of applying equal gain at all ISO settings (or at all settings from 200 up, or all from 400 up) and then scaling up appropriately in the raw-to-JPEG conversion is as consistent with the ISO and CIPA standards as always applying gain in direct proportion to the ISO setting, so that the same raw-to-jpeg mapping is used at all ISO settings.

According to your rather condescending analysis, Eric is not the only one totally confused by the Ssat standard. I am in company with him. :-[

I don't have access to the ISO documents, but must rely on the summary (https://en.wikipedia.org/wiki/Film_speed#Digital_camera_ISO_speed_and_exposure_index) of them posted on Wikipedia. As I understand things, the Ssat standard was carried over from the ISO 12232:1998 standard, and it has nothing to do with JPEG output,  sRGB, or the camera light metering. It is defined by the exposure in lux-seconds necessary to result in a given sensor saturation. It is defined as Ssat = 78 lux-sec/Hsat, where Hsat is the exposure necessary to saturate the sensor. The factor 78 was chosen such that exposure settings based on a standard light meter and an 18-percent reflective surface will result in an image with a grey level of 18%/√2 = 12.7% of saturation. The factor √2 indicates that there is half a stop of headroom to deal with specular reflections that would appear brighter than a 100% reflecting white surface. This is standard used by DXO and with which you find fault.

A standard exists so that one may obtain the same results when one uses that standard when working with different cameras. If differing amounts of highlight headroom are allowed, when working with raw files, one would obtain differing amounts of sensor saturation and ETTR exposure would be complicated. This post (http://www.dpreview.com/forums/post/50201960) by Jack Hogan is consistent with my interpretation of the Ssat standard, and I would appreciate your comments.

Regards,

Bill
Title: Best ISO for IQ280
Post by: dchew on July 12, 2015, 10:14:14 am
Kudos and many thanks to BJL and others for providing some expertise here.

So despite this thread meandering long and far away from the OP’s original question and the many rants (mine included), I’ve learned some things (I think!).

- When set at 200 ISO, my back shoots the same raw data it does at 35-100. I did not know that, and I don’t know when it started doing that. For all I know it always has. In my defense I can’t remember the last time I seriously used an ISO setting above 100. More on that later…

- “Base ISO” (or I suppose any other camera ISO setting) is not some sacrilegious specification. Camera ISO setting is useful to the photographer for taking pictures, but not for comparing cameras without interpretation. Frankly I never used sensitivity graphs for making a buying decision. Some here think photographers use these ISO graphs for that purpose, which brings me to my rant.

To Edmund and Sunli:
I might agree that on a consumer level, DSLR’s are compared, and perhaps choices are actually made on which DSLR to purchase, based on specs. But I will never believe that is the case with MFD backs, especially those from Phase One.

So I, pretty emphatically, do not agree with these statements:
“ISO 35 is just marketing”
“Phase… understand that cameras are often bought on specs”
“These numbers in the specifications play a significant role for marketing.”
“Phase is getting customers based on this spec (who here apart from some experts would buy an ISO 35 fixed-ISO back)?”

Just look at one of the most important characteristics of their marketing materials. Successful marketing materials need several things and one of the most important is a call to action. After a potential buyer interacts with a brochure, website, ad, salesperson, whatever, what is it precisely you want that potential buyer to do? Do you want them to pick up the phone and call? Write a cheque? Add the product to their shopping cart? Take a test drive? What??

Go to B&H and add that IQ380 to your shopping cart – oh wait, you can’t do that can you? Why do you think that is? Do you really think it is because their dealer network is almighty powerful and won’t let them do it? Nope. If Phase thought they would sell more stuff through those retailers they would. Now think about their marketing strategy: Pricing, distribution network, product feature set, and call to action in their marketing materials.  It is pretty clear that the central call to action is The Demo.

Better yet, attend a PODAS workshop, which has been a reasonably successful marketing program Phase One “sponsors.” You arrive and after the usual introductions and logistics, you are handed a camera. For the next 45 minutes or so you fumble around taking random photos and learning where and what the switches and dials do while technicians run around helping. Then you pack everything up and head out to some fantastic location and start taking photos. From that moment on the whole workshop is about the photographs; it is not about the camera. People are taking photos, processing photos, eating, drinking and discussing photos. Nobody is running around whispering, “This camera is amazing because it will do this at that ISO.”

The marketing slight of hand at PODAS is not about some spec, it is that you are in a beautiful location with great light and could take stunning photos with an iPhone or any other camera. Again, it is about the demo and about the photographs.

BTW, I would buy a fixed ISO 35 camera, and essentially did (and paid a lot for it!). I'm serious that I cannot remember when I've ever used anything higher than ISO 100, and I’ve loved every minute of it. Do I wish it had Sony-sensor dynamic range? Of course! But Sunli, I don’t think saying the IQ180 has great dynamic range is a false statement. It is certainly not as good as other cameras, but almost all cameras have great dynamic range in my opinion. I opened the freezer the other day and pawed through a bunch of film I still have in there to get at something. Only one type of film in there, and it is ISO 50. Did I used to use other film? Sure I did but not very often. So for me, buying a “fixed ISO camera” wasn’t that much different than what I had been doing all along!

I don’t sell cameras, but I strongly believe very few if any of these backs are sold because of some spec in an ad or brochure. The idea that the way Phase uses ISO settings is purely a marketing gimmick, and is therefore the only the reason they still exist (because no sane person would actually want or use their products if they new “the truth”) is 180 degrees away from everything I see in their marketing strategy. And everything I experience with the product.

Dave
Title: Re: Once again: the SSat minimum recommended EI is meaningless to ISO settings!
Post by: BJL on July 12, 2015, 10:47:29 am
Bill, I have no substantial disagreement with your description of the SSat measurement procedure (just one quibble, below).  My complaint is that the intent and appropriate usage of this measurement is not what some people think it is.

Specifically, it is intended (and best used) as a measure of one extreme of the range of suitable exposure levels: the maximum exposure level and thus the minimum exposure index corresponding to a guideline for a minimum advisable amount of exposure headroom -- an amount that is fine in many common situations like uniformly lit scenes, but which can fail badly when the metering is dominated by a shaded subject but there are parts of the scene that are in direct sunlight and are far brighter.

My main claim is that is a bad idea to use this recommended minimum as an ideal or standard, and wrong to say that this is what the ISO standard intends: especially at higher ISO settings, where it increases the risk of blown highlights while giving no IQ advantage in noise or such over somewhat lower raw placements.  No surprise that almost every camera maker using modern high DR sensors allows more than this minimal highlight headroom!

Whatever the virtues of standardization, this extreme value would be a vey poor choice for camera makers to standardize on in light metering (and to repeat, the ISO never intended that!)  Also the standardization (to mid-tones at about 12.5% of maximum raw level) can be and effectively is handled with EXIF info for "level placement intent", which effectively specifies where the mid-tone placement when it deviates from "12.5%".

For photographers who practice careful ETTR placement, SSat (and the DXO measurement) is clearly a useful measurement to know -- just not one that should be embodied in the operation of the ISO dial setting or as a mandate prohibiting a camera maker from providing more than this somewhat minimal amount of highlight headroom it its raw files, to the detriment of anyone wanting to use default JPEG conversions some of the time.

I don't have access to the ISO documents, but must rely on the summary (https://en.wikipedia.org/wiki/Film_speed#Digital_camera_ISO_speed_and_exposure_index) of them posted on Wikipedia.
Me too mostly, but I have also found some other useful discussion by industry experts in slides from seminar presentations and such; I posted them in another thread a long time ago, and will try to find them for you.

As I understand things, the Ssat standard was carried over from the ISO 12232:1998 standard, and it has nothing to do with JPEG output,  sRGB, or the camera light metering. It is defined by the exposure in lux-seconds necessary to result in a given sensor saturation. It is defined as Ssat = 78 lux-sec/Hsat, where Hsat is the exposure necessary to saturate the sensor. The factor 78 was chosen such that exposure settings based on a standard light meter and an 18-percent reflective surface will result in an image with a grey level of 18%/√2 = 12.7% of saturation. The factor √2 indicates that there is half a stop of headroom to deal with specular reflections that would appear brighter than a 100% reflecting white surface. This is standard used by DXO and with which you find fault.
My quibble is that DXO applies this to raw levels after possible amplification, so it is not always measuring sensor saturation, but instead at higher ISO settings is usually measuring where amplifier or ADC clipping occurs.  However, I think that the original objective of ISO:12232(1998) was indeed measuring saturation of the sensor's photo-sites, and this is probably what DXO's measurements still do at the lowest ISO setting, which is the main subject of debate in this thread.  So I would take DXO's measurement at a camera's lowest ISO setting as a measure of sensor saturation, and thus as a reasonable and useful measure of the sensor's base or minimum exposure index -- "base ISO" as it is sometimes called.  (But if instead you want a measure comparable to ASA/ISO film speed, the ISO 40:1 measure is it, as that Wikipedia article you mention explains.)
Title: Re: Best ISO for IQ280
Post by: BJL on July 12, 2015, 11:00:48 am
- When set at 200 ISO, my back shoots the same raw data it does at 35-100. I did not know that, and I don’t know when it started doing that. For all I know it always has. In my defense I can’t remember the last time I seriously used an ISO setting above 100. More on that later…
That seems to be so, and I see what this is puzzling and even bothersome to people who usually choose exposure settings manually based on the histogram or spot metering of highlihgt or some other careful strategy.  The only explanation I can offer is that:

a) These different low ISO exposure index settings (35, 50, 100, 200?) that use the same gain and so give the same raw levels when using the same exposure settings are primarily for convenience when using the in-camera meter.

b) They can also be of value with in-camera review, and when using live view: the same f-stop and shutter speed could be used with (i) ISO 50 with the light meter calling it one stop underexposure), (ii) ISO 100 ("on meter") or (iii) ISO 200 ("one stop overexposure") and give the same raw file, but the live view and rear-screen review would differ in brightness: using the ISO setting for which the light meter agrees with your exposure settings probably gives the most convenient review/preview image.
Title: Re: Best ISO for IQ280
Post by: bjanes on July 12, 2015, 11:18:16 am
Go to B&H and add that IQ380 to your shopping cart – oh wait, you can’t do that can you? Why do you think that is? Do you really think it is because their dealer network is almighty powerful and won’t let them do it? Nope. If Phase thought they would sell more stuff through those retailers they would. Now think about their marketing strategy: Pricing, distribution network, product feature set, and call to action in their marketing materials.  It is pretty clear that the central call to action is The Demo.

Another take on this: you can't buy a Phase One camera from B&H for the same reason you can't buy a Rolex at Walmart. One does not buy a Rolex on specs. A $200 Seiko has better specs than a$5000 Rolex. The electronic movement of the Seiko is much more accurate than the mechanical movement of the Rolex, but people with the money buy the Rolex for prestige and pride of ownership. If you are at a business meeting or cocktail party with a Rolex on your wrist, that advertises that you have arrived and are among the elite and would not deign to buy a cheap watch from Walmart, the store that caters to the unwashed masses. You would be shopping at Tiffany's.

Admittedly, an IQ 180 does have some advantages over the Nikon D810, and the parallels of this analogy are not exact. However, the price:performance of the Phase over the Nikon is not favorable.

Bill
Title: Re: Best ISO for IQ280
Post by: DucatiTerminator on July 12, 2015, 12:08:57 pm
Assuming the D810 is the Seiko, and the Phase a Rolex, you still can't buy a D810 at Walmart either. ;)

Alvin

Sent from my iPhone using Tapatalk
Title: Re: Best ISO for IQ280
Post by: Paul2660 on July 12, 2015, 12:10:36 pm
Another take on this: you can't buy a Phase One camera from B&H for the same reason you can't buy a Rolex at Walmart. One does not buy a Rolex on specs. A $200 Seiko has better specs than a$5000 Rolex. The electronic movement of the Seiko is much more accurate than the mechanical movement of the Rolex, but people with the money buy the Rolex for prestige and pride of ownership. If you are at a business meeting or cocktail party with a Rolex on your wrist, that advertises that you have arrived and are among the elite and would not deign to buy a cheap watch from Walmart, the store that caters to the unwashed masses. You would be shopping at Tiffany's.

Admittedly, an IQ 180 does have some advantages over the Nikon D810, and the parallels of this analogy are not exact. However, the price:performance of the Phase over the Nikon is not favorable.

Bill

Hi Bill,

Good points.  Back in 2008, it was easy for me to make the Phase One decision, as they were the only "affordable" solution for 39MP, single frame non-uprezed images.  The 60MP and 80MP backs still hold this especially the 80MP as far as the kings of resolution.  I personally have yet to find any software uprez solution that can get close the the native 60 or 80MP resolution from a Phase One.  Do I need 100MP, no can't justify that, not now with my current business.  To me improvements that the 35mm DSLR cameras have made since 2008 are very impressive and I feel that we will continue to see such price performance.

To the folks that have really applied the technical knowledge to this post, I do want to thank you.  I rarely print out a post but this one I did.  A ton of good information and I do appreciate the time it took for you to post it.  I have been trying to get my hands around the ISO settings of the Phase One backs, and never found a good technical doc.  But this post has it in spades and backs it up with a lot of great graphs and images.

It will help me in the future with my photography with the Phase backs I use.

Thanks
Paul Caldwell
Title: Re: Best ISO for IQ280
Post by: bjanes on July 12, 2015, 12:38:03 pm
Assuming the D810 is the Seiko, and the Phase a Rolex, you still can't buy a D810 at Walmart either. ;)

Alvin

Sent from my iPhone using Tapatalk

Really? They (Walmart) advertise the D810 online (http://www.walmart.com/ip/Nikon-36.3-MP-1542/37689286) for $2996.95. It would be shipped from OneCall, but it is still available by ordering from Walmart. However, you are mis-stating the intent of my analogy, where B&H is the mass-market option corresponding to Walmart and Tiffany is the exclusive retailer corresponding to Capture Integration or other Phase One dealers. I don't think you can buy an IQ180 from Tiffany. :) Bill Title: Re: Once again: the SSat minimum recommended EI is meaningless to ISO settings! Post by: bjanes on July 12, 2015, 01:09:53 pm Bill, I have no substantial disagreement with your description of the SSat measurement procedure (just one quibble, below). My complaint is that the intent and appropriate usage of this measurement is not what some people think it is. Specifically, it is intended (and best used) as a measure of one extreme of the range of suitable exposure levels: the maximum exposure level and thus the minimum exposure index corresponding to a guideline for a minimum advisable amount of exposure headroom -- an amount that is fine in many common situations like uniformly lit scenes, but which can fail badly when the metering is dominated by a shaded subject but there are parts of the scene that are in direct sunlight and are far brighter. My main claim is that is a bad idea to use this recommended minimum as an ideal or standard, and wrong to say that this is what the ISO standard intends: especially at higher ISO settings, where it increases the risk of blown highlights while giving no IQ advantage in noise or such over somewhat lower raw placements. No surprise that almost every camera maker using modern high DR sensors allows more than this minimal highlight headroom! Whatever the virtues of standardization, this extreme value would be a vey poor choice for camera makers to standardize on in light metering (and to repeat, the ISO never intended that!) Also the standardization (to mid-tones at about 12.5% of maximum raw level) can be and effectively is handled with EXIF info for "level placement intent", which effectively specifies where the mid-tone placement when it deviates from "12.5%". For photographers who practice careful ETTR placement, SSat (and the DXO measurement) is clearly a useful measurement to know -- just not one that should be embodied in the operation of the ISO dial setting or as a mandate prohibiting a camera maker from providing more than this somewhat minimal amount of highlight headroom it its raw files, to the detriment of anyone wanting to use default JPEG conversions some of the time. Me too mostly, but I have also found some other useful discussion by industry experts in slides from seminar presentations and such; I posted them in another thread a long time ago, and will try to find them for you. My quibble is that DXO applies this to raw levels after possible amplification, so it is not always measuring sensor saturation, but instead at higher ISO settings is usually measuring where amplifier or ADC clipping occurs. However, I think that the original objective of ISO:12232(1998) was indeed measuring saturation of the sensor's photo-sites, and this is probably what DXO's measurements still do at the lowest ISO setting, which is the main subject of debate in this thread. So I would take DXO's measurement at a camera's lowest ISO setting as a measure of sensor saturation, and thus as a reasonable and useful measure of the sensor's base or minimum exposure index -- "base ISO" as it is sometimes called. (But if instead you want a measure comparable to ASA/ISO film speed, the ISO 40:1 measure is it, as that Wikipedia article you mention explains.) Thanks for the clarification and additional information. DXO does not publish their raw data and how they obtain some of their results is not defined publicly, and the "ISOs" above base ISO obviously do not measure sensor saturation but merely clipping in the ADC. Setting the ISO on the camera to a value above base does not change the sensor sensitivity. In a previous exchange with you I did a careful reevaluation of my D800e at base ISO of 100. Since ISO settings are usually in increments of 0.33 there will well be some rounding error. The real base ISO may be 100 ± 0.33 EV steps. I do not have a calibrated light source and must assume that the camera meter is according to ISO 2720 with a Κ of 12.5, which I understand is the case. A target exposed according to the light meter with the camera set at ISO 100 results in 10.3% sensor saturation, which would allow 0.8 stops of highlight headroom as compared to the 0.5 EV specified in the Ssat standard. The EXIF indicated that the REI standard was employed, so Nikon can use any headroom allowance the desire, just as Phase One can use 1.5 EV without any trickery or dishonesty. IMHO, the REI standard is not a standard at all. DXO claim that they use 78 lux-sec in their calibration, but is this really so? For the D800e they rate measured ISO at 73 with a manufacturer value of 100. The difference is 0.45 EV, which would be on top of the already allowed 0.5 EV for a total of 0.95 EV. What numerator did they use for the ISO calculation? Regards, Bill Title: Re: Best ISO for IQ280 Post by: BJL on July 12, 2015, 01:31:04 pm Bill, just two comments: 1) Yes, the ISO and CIP standards actually specify that all values should be rounded to numbers in the standard sequence . . . 25, 32, 40, 50, 64, . . . (so that for example the minimum ISO setting of 32 for the IQ280 is exactly what is prescribed for the exact value of 29 reported by DXO.) 2) REI sounds very slippery, but there is a clause in there that seems to require it to be the same as SOS when the camera is in a "traditional (i.e. simple)" metering mode like center-weighted. So the flexibility in REI might only be for "non-traditional" modes like multi-zone metering, for which SOS seems inapplicable. So my hopeful guess is that any camera like the D800e that has both "traditional" and "non-traditional" metering modes does use SOS for the former, but has to describe its method as REI due to doing things differently in those exotic modes. Title: Re: Best ISO for IQ280 Post by: Ken R on July 12, 2015, 10:10:31 pm This guy explains it pretty well I think: HERE (http://www.clarkvision.com/articles/iso/) Title: Re: Best ISO for IQ280 Post by: DucatiTerminator on July 12, 2015, 10:58:49 pm Really? They (Walmart) advertise the D810 online (http://www.walmart.com/ip/Nikon-36.3-MP-1542/37689286) for$2996.95. It would be shipped from OneCall, but it is still available by ordering from Walmart. However, you are mis-stating the intent of my analogy, where B&amp;H is the mass-market option corresponding to Walmart and Tiffany is the exclusive retailer corresponding to Capture Integration or other Phase One dealers. I don't think you can buy an IQ180 from Tiffany.  :)

Bill

Relax, Brotha, it was meant as a joke, hence the emoticon. You can buy almost anything at rakuten.com, but most items are fulfilled by other vendors/dealers. I suspect this is not dissimilar to items Walmart does not fulfill themselves.

That said, no misstatement intended.. I really didn't read too much into your analogy or I would have pointed out that there is a much larger disparity between Walmart and Tiffany merchandise/brands vs. that of B&amp;H and CI/DT/etc.

I apologize if I misunderstood your reply, but I was sent to this forum to learn from some very skilled and artistic knowledgeable photo enthusiasts. So far it seems that there are a lot of egos hellbent on proving themselves right.

Alvin

Sent from my iPhone using Tapatalk
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 13, 2015, 01:19:07 am
Hi,

Yes, those articles are excellent. Pretty much of my initial understanding is coming from that.

This is another article often referred to, which I feel is more clear: http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/

Much of the later discussion relates to different ISO standards. Saturation based ISO is a solid standard, but there are a lot of variants not based on sensor saturation but on acceptable noise levels in JPEG or TIFF images.

The problem with those standards is that they give a lot of leeway for setting quite arbitrary values. For instance, this link compares the Pentax 645Z with the Phase One IQ-250 : http://home.comcast.net/~NikonD70/Charts/PDR.htm#Pentax%20645Z,Phase%20One%20IQ250 , a screen dump is attached.

Now, both cameras use the same sensor but show very different ISO dependency. The sensors use internal on chip raw conversion and there is probably very little difference between the two. The two curves meet at minimum ISO. This essentially means that Phase One uses a different ISO with additional highlight protection, while Pentax probably is very close to saturation based ISO. Also note that Phase One stops at 6400 ISO while Pentax goes up to 256000 ISO. How can that be?

Some consideration to put things in perspective:

Signal / Noise is essentially the square root of captured photons. If we assume 12.5% reflections exposure would be at least three stops below saturation.

If we assume that each pixel can hold 65000 electron charge, corresponding to 65000 photons (or so):

SNR = sqrt(65000 * 0.125) = 90

Now, add 1.5 stops of highlight protection:

SNR = srqt(6500 * 0.125 * 0.35) = 53 which still is a very good value.

The different JPEG/TIFF based ISO standards see to use SNR 40 as a limit.

Another way to see it is that the IQ-250 has 1.68 times the area of a 24x36 sensor, so it can give same SNR as a 24x36 sensor with 0.75 EV less exposure.

Saturation based ISO gives a lot of usable information for determining exposure. A more lax implementation/interpretation of ISO makes it much less usable.

Best regards
Erik

This guy explains it pretty well I think:

HERE (http://www.clarkvision.com/articles/iso/)
Title: Re: Best ISO for IQ280
Post by: voidshatter on July 13, 2015, 02:20:55 am
Hi Erik,

The IQ250 is 16-bit while the 645Z is 14-bit. Could it be the reason why the IQ250 can implement the extra highlight headroom at ISO 200?
Title: Roger Clark on what the ISO setting on a camera does, and "ISOless range"
Post by: BJL on July 13, 2015, 06:10:30 am
This guy explains it pretty well I think:

HERE (http://www.clarkvision.com/articles/iso/)
Yes, Roger Clark is a good source, and that looks like a good discussion of what the ISO setting on a camera does (adjusts gain, in conversion to raw and/or later in conversion to JPEG).

Some small quibbles with his Myth #1:
- the ISO setting does affect what the ISO and CIPA standards call "Output Sensitivity", which is the ratio between how much exposure the sensor gets and the final (JPEG?) output levels.
- the ISO setting can effect what I will call the overall "system sensitivity" in the sense of the ISO 40:1 or 10:1 measures related to SNR at a given signal level: this happens in what Clark calls the "camera electronics limited" lower ISO settings.
But I agree with his intended point that the ISO setting does not effect the sensitivity of the photo-sites themselves.

I would like Roger Clark to get or test some non-Canon cameras!  I would be interested to see his analysis of them.
Title: Re: Best ISO for IQ280
Post by: eronald on July 13, 2015, 08:23:41 am
Maybe using a single ISO number to characterize complex behaviour is not so smart

Edmund
Title: Re: Best ISO for IQ280
Post by: BJL on July 13, 2015, 09:18:25 am
Maybe using a single ISO number to characterize complex behaviour is not so smart.
Agreed: maybe that's why the ISO standard 12232(2006) defines at least four "numbers", measuring different aspects of sensor and camera performance.
Title: Re: Best ISO for IQ280
Post by: ErikKaffehr on July 13, 2015, 12:56:39 pm
Hi,

Here in Sweden I can buy both Phase One and Hasselblad on mail order.

Scandinavian Photo is like B&H : https://www.scandinavianphoto.se/kategori/1008167349/mellanformat/digitalt-bakstycke#brand=551,5661440&filter=&category=1008167349&page=0

Goecker used to be a store for professionals: http://webshop.goecker.se/web/guest/shop/-/schcategory/id/13197

Best regards
Erik

Really? They (Walmart) advertise the D810 online (http://www.walmart.com/ip/Nikon-36.3-MP-1542/37689286) for \$2996.95. It would be shipped from OneCall, but it is still available by ordering from Walmart. However, you are mis-stating the intent of my analogy, where B&H is the mass-market option corresponding to Walmart and Tiffany is the exclusive retailer corresponding to Capture Integration or other Phase One dealers. I don't think you can buy an IQ180 from Tiffany.  :)

Bill