Best ISO for IQ280

[BernardLanguillier]

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

[ErikKaffehr]

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

[voidshatter]

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. Where is your proof of ISO 32 having lower dynamic range than ISO 64 for D810?

c) Bill Claff 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.

[voidshatter]

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.

[ErikKaffehr]

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.

[synn]

If a photon shat in a void and there's no one around to capture it, would ISO settings make a difference?

[eronald]

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

[Christopher Sanderson]

If the tone of this discussion continues in this manner, the topic will be locked. Posters hidden behind pseudonyms will be banned.

[voidshatter]

Just realized that this forum requires real names, so I change my on-screen name from voidshatter to my real name. 

[Christopher Sanderson]

The use of 'Real Names' is a strong suggestion 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.

Back to topic...

[AlterEgo]

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"...

[BJL]

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.

[Ken R]

Sums it up it nicely:

https://www.youtube.com/watch?v=PHYidejT3KY

 

[Guillermo Luijk]

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).

Regards

[voidshatter]

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

[BJL]

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.

[voidshatter]

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?

[Guillermo Luijk]

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

[BJL]

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!

[voidshatter]

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?