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Author Topic: Best ISO for IQ280  (Read 53467 times)

voidshatter

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Re: Best ISO for IQ280
« Reply #140 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
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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.
« Last Edit: July 10, 2015, 05:20:06 pm by Yunli Song »
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ErikKaffehr

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Re: Best ISO for IQ280
« Reply #141 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

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dchew

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Re: Best ISO for IQ280
« Reply #142 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
« Last Edit: July 11, 2015, 12:47:38 am by dchew »
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voidshatter

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Re: Best ISO for IQ280
« Reply #143 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+

instead of what now Phase One advertises as:

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.
« Last Edit: July 10, 2015, 06:40:55 pm by Yunli Song »
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DucatiTerminator

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Re: Best ISO for IQ280
« Reply #144 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+

instead of what now Phase One advertises as:

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
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voidshatter

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Re: Best ISO for IQ280
« Reply #145 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.
« Last Edit: July 10, 2015, 07:04:16 pm by Yunli Song »
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DucatiTerminator

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Re: Best ISO for IQ280
« Reply #146 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
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Steve Hendrix

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Re: Best ISO for IQ280
« Reply #147 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
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ErikKaffehr

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Re: Best ISO for IQ280
« Reply #148 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:
http://www.dxomark.com/About/In-depth-measurements/Measurements/ISO-sensitivity

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
« Last Edit: July 11, 2015, 03:37:55 am by ErikKaffehr »
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Chris Livsey

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Re: Best ISO for IQ280
« Reply #149 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.
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ErikKaffehr

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Re: Best ISO for IQ280
« Reply #150 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.
« Last Edit: July 11, 2015, 05:27:31 am by ErikKaffehr »
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Chris Livsey

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Re: Best ISO for IQ280
« Reply #151 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 !!



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eronald

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Re: Best ISO for IQ280
« Reply #152 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 !!

« Last Edit: July 11, 2015, 06:36:44 am by eronald »
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Re: IQ280 and A99 have minimum EI within ISO recommended limits, D810 no
« Reply #153 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.
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voidshatter

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Re: IQ280 and A99 have minimum EI within ISO recommended limits, D810 no
« Reply #154 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".
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Ken R

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Re: Best ISO for IQ280
« Reply #155 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+

instead of what now Phase One advertises as:

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:

« Last Edit: July 11, 2015, 07:55:56 am by Ken R »
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ErikKaffehr

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Re: Best ISO for IQ280
« Reply #156 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 !!




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Erik Kaffehr
 

ErikKaffehr

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Re: Best ISO for IQ280
« Reply #157 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:


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BJL

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Re: Best ISO for IQ280
« Reply #158 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.
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sbernthal

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Re: Best ISO for IQ280
« Reply #159 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.
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