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

[tgray]

Joofa, just post your matlab script so people can see what calculations you did.

[tho_mas]

Hey, I had a typo in my text you quoted. I mentioned Prophoto at a place where I wanted to say Adobe. Please correct. I edited the original message.

I did understand it even without your correction.
A "ProPhoto D65" does not exist anyway...

[tho_mas]

White is white!

interresting claim 

[joofa]

I did understand it even without your correction.
A "ProPhoto D65" does not exist anyway...

Gosh, all effort in vain. Conceptually, there is NO difference between Prophoto RGB (D50) and Prophoto RGB (D65), both can be conceived with the same exact thought!

Joofa

[joofa]

Joofa, just post your matlab script so people can see what calculations you did.

Yes, I am thinking along the lines. But after some verification and rechecking of numbers. BTW, it is not Matlab. 

Joofa

[tho_mas]

Conceptually, there is NO difference between Prophoto RGB (D50) and Prophoto RGB (D65), both can be conceived with the same exact thought!

so a profile based on ProPhoto primaries but with D65 defined as white point... or a ProPhoto that has been mapped to D65?

[Manuel_A]

Hi Joofa,

Ok I will bite, what’s the girls name…

[tgray]

Yes, I am thinking along the lines. But after some verification and rechecking of numbers. BTW, it is not Matlab. 

Ahh, it looked like it from the images.

[MarkM]

So that's it Joofa?

You post a graph, which you claim demonstrates that commercial software and color authorities are wrong about a very fundamental idea that is generally held as common knowledge. You continually tell people just to look at the graph.

You say :

Anybody can produce the plots that I have done using basic plotting tools

When somebody does you answer:

it is quite an involved issue. You want to go into the mechanics. It can take at least one entirely different thread, or several, as there are many issues here.

It's very hard to take anything you are posting seriously if you won't make a serious effort to say anything other than 'my graph proves it; look ay my graph.' A lot of people in this thread have taken a lot of their time to make cogent, easy-to-read arguments. Because many of the arguments are direct and clear, it should be easy to make an equally direct clear point about why they are wrong. But you are either unable or unwilling to do that. When presented with a clear argument, you either post your graph again, or you say 'nope', or you redirect with talk of hilbert space and the like.

I would have to go back through all the posts to verify this, but I think I'm the only one so far that has been willing to do the matrix algebra with you and try to form a clear explanation of your methods, but you don't seem to want that. Which makes me think you don't actually want people to understand what is behind your claim.

[joofa]

So that's it Joofa?

You post a graph, which you claim demonstrates that commercial software and color authorities are wrong about a very fundamental idea that is generally held as common knowledge. You continually tell people just to look at the graph.

Mark, please don't put words in my mouth. I never said they are "wrong". At one place, in a guess work, I referred to gamut being "twisted". But trust me even if the gamut in those utilities is twisted, it does not make them wrong. It won't start showing in-gamut colors out-of-gamut and vice versa. No. It is referring to a very different fact. I just happened to mention it. It has no connection to figuring out which are in/out of gamut colors between Adobe RGB and Prophoto RGB.

See, that is one thing I don't like. I have tried to be very careful with language. But people have been putting words in my mouth all along. I repeat I am not claiming any xyz commercial utility is wrong.

Next, I said that I shall work on cleaning code, verifying things again, writing it in a document, and put it somewhere online when that is done. Please be patient.

Sincerely,

Joofa

[joofa]

If anybody thinks that I am not leading them in the right direction then come on guys, after writing those long messages, going over several times how to interpret white points, how to construct different spaces in the same volume, and presenting graphs, and providing detailed explanations with clear matrix algebra, then it is being very unfair.

Joofa

[eronald]

I don't know about the rest of this thread, but this argument here is ... unexpected. And probably correct and interesting.

I could probably understand the maths but cannot be bothered - I'll believe you anyway.

Edmund

OK Joofa, lets figure it out. I'll start by paraphrasing what I think you are getting at. Although you keep saying people don't understand your graph, I think most people with any colorimetric education do. So I explain what I think you saying and you can correct me if I'm wrong. OK?

So we take the unit RGB values from each space:
R= [1, 0, 0]
G = [0, 1, 0]
B = [0, 0, 1]

And we convert them to XYZ values via an absolute colorimetric rendering for each color space in question. This essentially creates three axis representing three coordinate systems: the XYZ space is indicated by the main axis of the cube in your projection. The three coordinate systems are related via an affine transformation, so the relationship is linear.

Now the way 3D coordinates are normally plotted on a 2D diagram only gives you one perspective. If you look straight down the Z axis you will see the plot like the first attachment. The blue dots are the AdobeRGB primaries; the red dots are the ProPhoto primaries. I've circled the blue primary. Looking at this graph, it appears that the AdobeRGB primaries are completely contained within the Prophoto RGB primaries.

But here's the twist: since this is a three dimensional plot projected into two dimensions, we don't get the whole picture. The second attachment shows what it looks like if we rotate the space and look straight down the X axis instead. (Pay attention to the labeled axis). Now you can see that the blue primary (circled) actually falls outside of the triangle formed by the ProPhoto apices. In three dimensional space that blue primary actually falls outside the solid formed by the ProPhoto primaries. Which is to say it is out of gamut.

Since a chromaticity diagram only shows two dimensions of a three dimensional space, we often don't get the whole picture. This is especially important when comparing gamuts because you are only seeing one slice of a three dimensional volume.

Does this accurately represent what you are getting at Joofa?

[joofa]

It's very hard to take anything you are posting seriously if you won't make a serious effort to say anything other than 'my graph proves it; look ay my graph.' A lot of people in this thread have taken a lot of their time to make cogent, easy-to-read arguments. Because many of the arguments are direct and clear, it should be easy to make an equally direct clear point about why they are wrong. But you are either unable or unwilling to do that. When presented with a clear argument, you either post your graph again, or you say 'nope', or you redirect with talk of hilbert space and the like.

Mark, are you forgetting that Iliah Borg, Peter (DPL), Jc1, and perhaps a few others have independently verified what I said. Come on. I could have stated my findings without showing any graph and it would have been the same result stating the relationship of in/out of gamut colors between the said spaces.

Joofa

[MarkM]

Mark, please don't put words in my mouth. I never said they are "wrong"

This is the fact that is under consideration as I understand it:
There are no colors in the Adobe1998 RGB space that cannot be reproduced in the ProPhotoRGB space. In other words the gamut of the ProPhoto RGB working space completely contains the Adobe1998 RGB space

This is a commonly-held belief. You claim the opposite.

The clearest expression of your goal that I have been able to find is this:

Have you not understood that the basic premise of my argument is to find color(s) that are represented in standardized Adobe RGB (D65) but not in standardized Prophoto (D50).

I read that to mean that you believe the fact under consideration (what I wrote in bold above) is wrong. I don't think the two statement are compatible. If that isn't what you are sayin—if you don't dispute the fact under consideration, if you don't think it's wrong, please tell us now and we can chalk it up to a big misunderstanding.

You continually assert that your graph demonstrates this, but you won't explain how the graph came to be. The graph has numbers along the outside but the axis aren't labeled. I've been assuming it's XYZ axis, but maybe that's a mistake on my part.

Maybe you can just  give us the coordinates of the six points in your graph. (Using the XYZ axis if that is in fact what the outside box is).

[MarkM]

Joofa, I think this would help people understand your graph:

Plot it as you have, but additional show where the point [.5, .5, .5] fall in each space.

[tho_mas]

Joofa...

attached are 2 sRGB profiles; the suffix is renamed to TXT (as ICC won't upload).
When you rename the suffix to ICC you can use them as icc profiles.
Now, when you compare them the same way you have compared AdobeRGB to ProPhotoRGB... are their gamuts fully contained in each other?

[joofa]

Mark, I don't know why you are cooking up stuff that I did not say. Please reread my messages. I have always maintained that I believe those utilities show the gamut of Adobe RGB (D50) within Prophoto (D50), which is my case (3) below. The point of contention has always been the gamut of Adobe RGB (D65) and Prophoto (D50), which is case (1).

Going back to my very first note:

Joofa wrote on DPReviw:

Fraction of unit stimulus blue ProPhoto RGB primary needed to match unit stimulus blue Adobe RGB primary:

(1) Adobe RGB white point=D65, PropPhoto RGB white point=D50, Fraction needed=1.2

(2) Adobe RGB white point=D65, PropPhoto RGB white point=D65, Fraction needed=0.91

(3) Adobe RGB white point=D50, PropPhoto RGB white point=D50, Fraction needed=0.88

(4) Adobe RGB white point=D50, PropPhoto RGB white point=D65, Fraction needed=0.67

Sincerely,

Joofa

EDIT: Highlighted the wrong case. Corrected.

[MarkM]

Mark, I don't know why you are cooking up stuff that I did not say.

Go ahead and quote from my post: what did I say that misrepresents you. I am really not trying to do that.

[joofa]

Go ahead and quote from my post: what did I say that misrepresents you. I am really not trying to do that.

Please reread my message #460. So surprised. It can't get any clearer than that!

Joofa wrote on DPReviw:

Fraction of unit stimulus blue ProPhoto RGB primary needed to match unit stimulus blue Adobe RGB primary:

(1) Adobe RGB white point=D65, PropPhoto RGB white point=D50, Fraction needed=1.2

(2) Adobe RGB white point=D65, PropPhoto RGB white point=D65, Fraction needed=0.91

(3) Adobe RGB white point=D50, PropPhoto RGB white point=D50, Fraction needed=0.88

(4) Adobe RGB white point=D50, PropPhoto RGB white point=D65, Fraction needed=0.67

Joofa

[Graystar]

...but I think I'm the only one so far that has been willing to do the matrix algebra with you and try to form a clear explanation of your methods, but you don't seem to want that.

I don’t even think that’s necessary.  He agreed with the B.L. Calculator calculations that Iliah provide in post #88...

http://www.luminous-landscape.com/forum/index.php?topic=49940.msg412428#msg412428
http://www.luminous-landscape.com/forum/index.php?topic=49940.msg412431#msg412431

To me it seems like the algebra, for the most part, is set.  The question is the validity of the algebra.

In the subsequent 2 pages of responses, of which you were a part of, you, digitaldog, and maybe a couple others tried to correct the mistake Iliah had made. Joofa will not consider any other process of converting the color.

This entire argument boils down to adaptation.  If you use adaptation, the blue is within Pro Photo, and if you don’t then it isn’t (or if you simply mess it up because you don’t realize what you’re doing on the calculator.)

Joofa doesn’t seem to care that the blue he started with appears different when trying to find its place in Pro Photo.  And that’s the core issue.  He only cares about numbers, and we care about the way the blue appears to a human.  It seems pointless to continue.