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Author Topic: attention color whizes: non-typical sRGB/RGB/ProPhoto question  (Read 94484 times)
tho_mas
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« Reply #680 on: January 10, 2011, 06:31:44 PM »
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That's not my understanding. Chromaticity coordinates are a 2D projection from the 3D XYZ space onto the unit triangle. They are not dependent on the white point.

The calculation normally given is:

x = X/(X+Y+Z)
y = Y/(X+Y+Z)
z = Z/(X+Y+Z)

(The CIE loved the letters x y and z for some reason)

This guarantees that x + y + z = 1 which makes one of the variables dependent on the other two. e.i. if you don't know z you can calculate it from x and y: z = 1-x-y So z is normally ignored.

You can take an ZYX coordinate like the blue primary: 0.1881852, 0.0752741, 0.9911085
and from it calculate the chromaticity coordinate: 0.0600 0.790 (rounded).
phew... that is the part that always esacpes me as a "user" :-)
However, thanks for the explanation!

Joofa.. after this long thread and in particular Mark's clear description of adaption 2 or 3 pages above... would you still phrase the following quotes in the same way?

Quote
http://www.luminous-landscape.com/forum/index.php?topic=49940.msg412938#msg412938
The reason Adobe RGB (50) can be contained is that because it has been chormatic-adaptation-transformed from Adobe RGB (D65), and this process has already stripped that offending blue Adobe RGB (D65) primary. After Bradford transformation Adobe RGB (D50) gets a new blue primary.

Quote
http://www.luminous-landscape.com/forum/index.php?topic=49940.msg412945#msg412945
Mark, I thought you were beginning to understand this process, but it seems you are derailing again. Grin The intent was to show that in linear transformations akin to absolute colorimetry, Adobe RGB (D65) contains saturated blue colors that have no representation in Adobe RGB (D50) or Prophoto RGB (D50).
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tho_mas
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« Reply #681 on: January 10, 2011, 06:33:19 PM »
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Edit:
I didn't see the images you uploaded. I'm not sure how PS goes about calculating the XYZ coordinates the colorthink shows. I would be interested to know.
honestly... I have no idea! But they are there...
Obviously the little matrix of Photoshops tool provides anything that is needed...?!
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joofa
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« Reply #682 on: January 10, 2011, 06:39:00 PM »
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Joofa.. after this long thread and in particular Mark's clear description of adaption 2 or 3 pages above... would you still phrase the following quotes in the same way?

Hi Tho_mas,

The issue is that it appears that some people have interpreted Mark's illustration to be the same/similar as mine. Perhaps because it seems to suggest that blue's are out of gamut as has been my basic premise from the start of this thread. However, I believe that Mark's illustration is incorrect. This is not how color spaces are "stitched" together. Actually, it is dangerous to think this is how the process work.

I still stand by all of my findings as reported here. So the two comments that you quoted from me stay unchanged.

Sincerely,

Joofa
« Last Edit: January 10, 2011, 10:26:56 PM by joofa » Logged

Joofa
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MarkM
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« Reply #683 on: January 10, 2011, 06:46:36 PM »
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The issue is that it appears that many people have interpreted Mark's illustration to be the same/similar as mine. Perhaps because it seems to suggest that blue's are out of gamut as has been my basic premise from the start of this thread. However, one must realize that Mark's illustration is incorrect. This is not how color spaces are "stitched" together. Actually, it is dangerous to think this is how the process work.

I still stand by all of my findings as reported here. So the two comments that you quoted from me stay unchanged.

You keep saying stuff like that Joofa, which is why this thread keeps getting derailed. Despite all the rancor in this discussion, I really am sincerely interested in knowing if and how I'm doing something incorrect. Since you refuse to explain even basic, fundamental aspects of your plot, we have no idea how to interpret it. I've tried several times to explain how I understand it, only to be told I am naively setting myself up for embarrassment without further explanation.

My plot might be completely wrong, sure. I think it agrees quite closely with Lindblooms grapher if you scroll down the page here:  http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.html (plotting the two profiles in XYZ looks the same to me). I understand the limitations of visualizing in ZYX space, but that doesn't seem to be what you are saying.

You are simply saying I am incorrect. Full stop. No explanation.
« Last Edit: January 10, 2011, 06:52:04 PM by MarkM » Logged

tho_mas
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« Reply #684 on: January 10, 2011, 06:48:34 PM »
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The issue is that it appears that many people have interpreted Mark's illustration to be the same/similar as mine.
I am not talking about the graph (but it tells something that you do).

Quote
one must realize that Mark's illustration is incorrect
so be it

Quote
I still stand by all of my findings as reported here. So the two comments that you quoted from me stay unchanged.
the question was whether you would phrase them in the same way. Do you think it's a good wording?

especially this one:
Quote
Adobe RGB (D65) contains saturated blue colors that have no representation in Adobe RGB (D50) or Prophoto RGB (D50)
AdobeRGB contains saturated blues that have a visuell representation in ProPhoto ... AdobeRGB get's a new primary in D50 SO THAT the blue colour looks the same (under changed lighting conditions). The colour is the same... only the coordinates of this same colour are different.

« Last Edit: January 10, 2011, 06:50:07 PM by tho_mas » Logged
joofa
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« Reply #685 on: January 10, 2011, 06:54:53 PM »
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the question was whether you would phrase them in the same way. Do you think it's a good wording?

Oh okay, I see, what you are saying. Sorry, for not understanding it first. I think Mark is headed in the right direction with the wording he used. I have to reread Mark's words again, but what I remember, I don't see an inherent contradiction in the process of adaption he has described and my two quotes you used above. I think Mark's intuition is right I just disagree with certain aspects of the physical process of color spaces.

I think it is a good start by Mark. If you notice this is quite similar to the process of adaption described in the pdf that Peter (DPL) quoted a while back. I have thought along the same lines for sometime and that is how I produced the numbers and my plot. So the bottom line is that I agree with Mark's thought but not the physics engineering  Grin behind it.

Sincerely,

Joofa
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Joofa
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tho_mas
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« Reply #686 on: January 10, 2011, 07:17:19 PM »
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I think Mark is headed in the right direction with the wording he used.
cool!

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I have to reread Mark's words again, but what I remember, I don't see an inherent contradiction in the process of adaption he has described and my two quotes you used above.
the problem is the word "colour".
When we agree that AdobeRGB's blue has an (adapted) visuell representation in ProPhoto... then we can look at the issues Iliah brought up.
Multiple whitepoints in a scene, rendering intends when proofing etc.
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Farmer
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« Reply #687 on: January 20, 2011, 05:43:40 PM »
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Saw this linked today:

http://www.inventoland.net/imaging/uc/slides.pdf

Was posted on http://www.mostlycolor.ch/
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dchew
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« Reply #688 on: January 21, 2011, 03:42:15 AM »
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And here is a related article to the slides above, which includes text describing some of Giordano's slides:
http://www.hpl.hp.com/techreports/2008/HPL-2008-109.pdf

Dave
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