attention color whizes: non-typical sRGB/RGB/ProPhoto question

[Graystar]

Again, there is no need to change the Ref. White setting. Leave it at D50 (or wherever),
but set Adaptation to None - right from the beginning. Interestingly enough BL's calculator offers this option.

You are failing to realize that when you set Adaptation to None, you are saying to use the white point of the selected RGB space.

Setting Adaptation to None (with any Ref White) is the same as using an Adaptation method and changing the Ref White in the middle of your conversion from D65 to D50.

When you convert Adobe to XYZ, the result is tristimulus values that are related to an illuminant.  If you select D65 with adaptation, or Adaptation None, then the illuminant is D65.  But it's just as valid to select a different illuminant, such as standard illuminant E, with adaptation.  You get different tristimulus values, but they’re related to a different illuminant.  The tristimulus values and the illuminant create the Adobe blue response in the eye.

But then, your next step is to change the illuminant...either directly in the calculator by selecting D50 (when using adaptation) or indirectly when using Adaptation None (the white point of the destination space will be used.)  When you do that you change the blue response in the eye, because the tristimulus values are the same but the illuminant is different.  It’s a different blue.  So you’re mapping a blue that has nothing to do with Adobe saturated blue, and then claiming that Adobe blue isn’t in Pro Photo.

This must be the hundredth time this has been explained.

[Peter_DL]

You are failing to realize ...

No, you fail to realize.
YOU are insistently presuming chromatic adaptation.
I'm considering it as an option, typically the preferred one, but not necessarily.

Example: some years ago I had problems with monitor calibration & profiling. Suddenly all images looked greenish to me (in a color-managed environment). Actually I was not really able to adapt to the new white point of my monitor. I didn't like it. It should have been unchanged D65, but that was obviously not the case anymore. In order to verify my impression I created a white patch, assigned my monitor profile and converted AbsCol to a D65 working space. The result was that R, G, B got different from each other, confirming that my monitor white wasn't D65. The rest turned out to be a handling error with the software package.

Peter

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[Graystar]

No, you fail to realize.
YOU are insistenly presuming chromatic adaptation.
I'm considering it as an option, typically the preferred one, but not necessarily.

Well, if we both understand what's happening and what it means, but simply have different views of the validity, then we're at an impasse.  We'll just have to agree to disagree.

[tho_mas]

Go back and read tho_mas' message and read my response to him.

for instance this one? -> http://www.luminous-landscape.com/forum/index.php?topic=49940.msg413842#msg413842
Well, it's a statement, not really an answer (i.e. you are not adressing my question).
My point of view: when all PropPhoto blues are clipping converting relcol or abscol to AdobeRGB as target this consequently means that there is no AdobeRGB blue that is outside of ProPhoto. If there would be a AdobeRGB blue value outside of ProPhoto the respective AdobeRGB blue value would not clip.
You say the gamuts fall outside of each other - consequently some AdobeRGB blues should not show clipping.
But all AdobeRGB blues show clipping. Why?

[tgray]

Well, it's a statement, not really an answer (i.e. you are not adressing my question).
My point of view: when all PropPhoto blues are clipping converting relcol or abscol to AdobeRGB as target this consequently means that there is no AdobeRGB blue that is outside of ProPhoto.

I'm not sure if this is a complete standalone thought, but I interpreted it as one.  If not, ignore what I say next.

If all Prophoto blues clip when converting to AdobeRGB relcol or abscol, that means those blues are not in AdobeRGB.  It does not mean that all AdobeRGB blues are (or are not) in Prophoto.

The analogy is squares and rectangles.  'All squares are rectangles' does not imply that 'all rectangles are squares.'

[Iliah]

> Are there cases when we don't actually want to apply a chromatic adaptation?  Iliah has mentioned yes several times.  How would one carry that out in practice?

In fact there is a strategy that is called multi-zone white balance in  RML (RawMagick Lite). The user has two options - to sample different neutrals across the scene and the algorithm will weight and average those; or to set different white balances for different zones with smooth transitions in between. Effectively it is some sort of control over chromatic adaptation. There are more modern strategies now, too.

Looking at paintings one can see how applying full chromatic adaptation can ruin a chef-d'oeuvre. El Greko, Levitan, Monet, ... Same about perspective, depth of filed (View to Toledo). All of those are creative instruments and can't be applied indiscriminately.

[joofa]

for instance this one? -> http://www.luminous-landscape.com/forum/index.php?topic=49940.msg413842#msg413842
Well, it's a statement, not really an answer (i.e. you are not adressing my question).
My point of view: when all PropPhoto blues are clipping converting relcol or abscol to AdobeRGB as target this consequently means that there is no AdobeRGB blue that is outside of ProPhoto. If there would be a AdobeRGB blue value outside of ProPhoto the respective AdobeRGB blue value would not clip.
You say the gamuts fall outside of each other - consequently some AdobeRGB blues should not show clipping.
But all AdobeRGB blues show clipping. Why?

Please see my reply #414 to you. There is at least one more reason also that I just mentioned casually in reply #418, which is involved, and I am not prepared to go in details here.

Sincerely,

Joofa

[Peter_DL]

... when all PropPhoto blues are clipping converting relcol or abscol to AdobeRGB as target this consequently means that there is no AdobeRGB blue that is outside of ProPhoto.

The inverse test works reasonably well with the Granger Rainbow posted many pages ago,
ProPhoto RGB blues do not clip when converting AbsCol to Adobe RGB
(within the limits that we can believe in oog marks).

Peter

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[MarkM]

Mark, since you're still around -- would you mind replying to reply #511?

Hi Emil,
I thought I did in a follow up here: http://www.luminous-landscape.com/forum/index.php?topic=49940.msg413941#msg413941

[Farmer]

Looking at paintings one can see how applying full chromatic adaptation can ruin a chef-d'oeuvre. El Greko, Levitan, Monet, ... Same about perspective, depth of filed (View to Toledo). All of those are creative instruments and can't be applied indiscriminately.

Interesting that you should mention Monet.  You're probably aware that after he had surgery to remove a cataract, he realised that he was seeing colours differently compared to his youth.  Painting with one eye he would describe a scene as blue/green in an area whereas with the other he would show orange/red.

In other words, the exact same scene can fall outside of its own gamut if you filter it incorrectly.

[Farmer]

Joofa:

You are utterly dismissing any attempts to argue against your hypothesis.  You have even dismissed some people as needing to learn more colour science.  Since you invoked the science of the matter, it is beholden to you for provision of data and method in order that your hypothesis may be tested - that we may attempt to falsify it.  Once that it is done, and assuming it stands up to the rigour of falsification, we can then attempt to discern if it fits with observation.  In such case, it may become a workable theory.

By continuing to refuse to provide your actual data ("it's on Google" isn't sufficient), and by simply saying, "but others have found it and worked it out and agreed" also doesn't stand up to scientific scrutiny, because until all parties share their data and method, we have no way of knowing if it's the same and no way of falsifying it.

[MarkM]

Mark, I have no personal vandetta against you. Because, if I did, then trust me you provided me with a wonderful opportunity to embarass you online with that proceedure of yours to determine gamuts, which was so patently incorrect and naive.

Joofa, I posted those in a sincere attempt to understand what you are saying with your graph. I put it all out there, explained specifically what I was doing, and then asked, "is this what you mean?" It was meant as an opportunity for you to tell me where I was going wrong. I wouldn't find it the slightest bit embarrassing to be wrong and if I'm naive, so be it. Please embarrass me if it means explaining in detail why that graph is important. I've tried to be very clear with everything I've posted here—this is because if I'm wrong, I want people to have enough information to show me exactly where I'm wrong. I don't want to post a bunch of half-committed ideas that are impossible to agree or disagree with.

But calling me naive and showing how I'm naive are two different things. Show me. Show us all. Be blunt, I can take it. I relish the chance to be embarrassed if it means you will clearly explain why that graph that you keep reposting is important to your point.

So, this is what I see on that graph (It's on page two of this thread):
• A three dimensional space with an unlabeled scale along the outer edges
• Six lines arranged inside the space connecting to the origin of the unlabeled space
• Labels indicating that the lines represent primaries from Adobe and ProPhotoRGB (although you've used the terms Adobe(D50) and Adobe(65) throughout the thread, so the label is a little vague.
• A line labeled 'spectral colors'

So you can continue to be cagey and vague about this or you can fill us in.

Here's a start:
•Do the numbers outside the box represent XYZ numbers?
•Which Axis is which?
•The endpoints of the vectors, presumably are XYZ coordinates (but that depends on the first question)—since you are clearly working with numbers, maybe you could just post the coordinates of the vectors. It's only six numbers, you can cut and paste.

[sandymc]

Using twisted profiles, do you have colour shifts when changing the value of exposure correction slider?

Depend where the twist is; if you were using twists to achieve non-linear sensor space to RGB conversion, you would structure the profile so as to position the twist before exposure correction, and not get color shifts on exposure correction. Which is different to using hue twists to achieve a particular look.

Sandy

[joofa]

Joofa, I posted those in a sincere attempt to understand what you are saying with your graph.

Is your idea of "sincere attempt to understand" accomplished by calling me a waste of effort, troll, mocking me several times, saying I'm setting up smoke screens, etc?

Here's a start:
•Do the numbers outside the box represent XYZ numbers?
•Which Axis is which?
•The endpoints of the vectors, presumably are XYZ coordinates (but that depends on the first question)—since you are clearly working with numbers, maybe you could just post the coordinates of the vectors. It's only six numbers, you can cut and paste.

No, it is not XYZ. And, I said that right there in my reply #396 to you.

Sincerely,

Joofa

[MarkM]

No, it is not XYZ. And, I said that right there in my reply #396 to you.

OK, that's a start. You've put numbers along the outside of the graph. What are those numbers?

[Iliah]

> if you were using twists to achieve non-linear sensor space to RGB conversion

Why would that be helpful?

[Graystar]

Hey Joofa!  Good news!  Everything is fine!  Look at this 3D L*a*b* display I produced from Gamutvision using the "Absolute" comparison method (it’s Gamutvision, what all the big names use for testing, so you know it has to be right.)  It shows that Abobe RGB (1998) is fully contained within Pro Photo.  So you have nothing to worry about!

[Iliah]

> Interesting that you should mention Monet.
Yes, the purpose of those three particular names was to give examples of three mane reasons.

> the exact same scene can fall outside of its own gamut if you filter it incorrectly.

Incorrectly or artistically.

[joofa]

Hey Joofa!  Good news!  Everything is fine!  Look at this 3D L*a*b* display I produced from Gamutvision using the "Absolute" comparison method (it’s Gamutvision, what all the big names use for testing, so you know it has to be right.)  It shows that Abobe RGB (1998) is fully contained within Pro Photo.  So you have nothing to worry about!

Graystar, I think at this stage it has become like beating a dead horse. Just look at the posts of Peter (DPL) to verify what has been said so far. I think discussion is now turning to the interesting area of when is chromatic adaptation not required.

Sincerely,

Joofa

[Graystar]

Graystar, I think at this stage it has become like beating a dead horse. Just look at the posts of Peter (DPL) to verify what has been said so far. I think discussion is now turning to the interesting area of when is chromatic adaptation not required.

No.  Please look.  The display is correct.  I can't overemphasize that fact.