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Author Topic: attention color whizes: non-typical sRGB/RGB/ProPhoto question  (Read 227683 times)

joofa

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #480 on: January 07, 2011, 07:34:12 pm »

My response was to Joofa.

I'm not interested in teaching at all and never was. What interests me is to help; mostly - to help people and ideas under attack from those who are only fit to play the leading role George Ruggle's piece.

Thank you very much for all the help. I really appreciate that.

Best regards,

Joofa
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jeremypayne

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #481 on: January 07, 2011, 07:35:10 pm »

My response was to Joofa.

I'm not interested in teaching at all and never was. What interests me is to help; mostly - to help people and ideas under attack from those who are only fit to play the leading role George Ruggle's piece.

Congratulations ... You helped prove "2" is greater than "1".

Never mind that we were discussing "weight" and comparing scales on the earth and the moon.

Nice work, Batman.
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MarkM

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #482 on: January 07, 2011, 07:38:27 pm »

From The Reproduction of Colour by R.W.G. Hunt (an excellent text btw)
Quote
It is thus clear that the inability of any beams of red, green, and blue light to stimulate the retinal cones separately introduces a basic complication into the whole of trichromatic colour reproduction. If the ρ and β curves did not overlap in the blue-green part of the spectrum, then green light could be found that stimulated the γ-cones on their own; but, since the ρ and β curves do overlap appreciably, the γ-cones cannot be stimulated on their own. For colour vision, this overlapping provides the basis for good detection of changes in hue throughout the spectrum. But, for colour reproduction, it means that simple trichromatic methods cannot achieve correct colour reproduction of all colours. The difficulty cannot be avoided, because it stems from the basic nature of human colour vision; the result is unwanted stimulations in reproduction systems.
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Iliah

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #483 on: January 07, 2011, 07:46:54 pm »

You helped prove "2" is greater than "1".

It is a simple (and well-known) joke to disprove, of course if one was listening in his first class on arithmetic.

The point that you are missing is that conversion with regards to white point and thus performing adaptation is not necessarily the only useful way, and it gets progressively less useful while target gamuts are getting larger. For certain media, certain image presentation sizes, and certain viewing conditions adaptation is not necessary at all - worse, it is counterproductive.

It is not wise going in circles. The case was presented. Bruce wrote what he wrote, supporting the case given certain limitations, like some whites which are not run through adaptation are not whites anymore. From our photography we know it is often so. Having lights with different CCTs in the scene is nothing new. Defending ProPhotoRGB as the widest and wisest and the only is something that motivates nay-sayers. Well, they are betting against technical progress and their argument is doomed.
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Iliah

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #484 on: January 07, 2011, 07:50:16 pm »

> Hold on, let me find it…
Trust me I know what you mean - but it does not change a thing.
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MarkM

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #485 on: January 07, 2011, 07:51:42 pm »

> Hold on, let me find it…
Trust me I know what you mean - but it does not change a thing.

I don't know what you mean. Change a thing about what?

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digitaldog

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #486 on: January 07, 2011, 07:53:45 pm »

Quote
The Reproduction of Colour by R.W.G. Hunt

Come on Mark, stick to salient points here. This Hunt guy was nothing until he stumbled on that Ketchup recipe and really made his claim to fame. ::) Now the Huntz book on color, that’s good reading.
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tho_mas

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #487 on: January 07, 2011, 07:54:34 pm »

It's more fundamental than that. You may be able to make a profile that can do crazy things and specify off the wall coordinates in LUTs, but you won't be able to actually reproduce the colors with only three primaries.
re cameras: you can create color spaces in D50 that do contain high saturated blues cameras can capture and that are not contained in ProPhoto.
Re the said HDR monitors: as devices they do produce colors, don't they? It's certainly doable to create table based profiles for these monitors (based on the colors they actually produce). If this is possible... it's certainly also possible to create "averaged" profiles that generally contain the gamut of these monitors (without containing imaginary colors).
A bit like Photogamut once was desinged as a table based working space targeted at printer gamuts: http://photogamut.org/E_idea.html
Something like that... just with a larger gamut.

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jeremypayne

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #488 on: January 07, 2011, 08:04:41 pm »

The point that you are missing

Actually, I'm not missing anything.

I'm sure there will be new models to map and describe the world of reflected light on recorded media ... And equally sure you have some insights into what that future looks like.

But you aren't doing much to get that across HERE.  That's the point you are missing.
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MarkM

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #489 on: January 07, 2011, 08:06:32 pm »

re cameras: you can create color spaces in D50 that do contain high saturated blues cameras can capture and that are not contained in ProPhoto.
Re the said HDR monitors: as devices they do produce colors, don't they? It's certainly doable to create table based profiles for these monitors (based on the colors they actually produce). If this is possible... it's certainly also possible to create "averaged" profiles that generally contain the gamut of these monitors (without containing imaginary colors).
A bit like Photogamut once was desinged as a table based working space targeted at printer gamuts: http://photogamut.org/E_idea.html
Something like that... just with a larger gamut.

Working spaces like Photogamut (if I understood what it was in my quick scan) can get away with a wider gamut because their primaries don't have to be real. ProPhotoRGB does this. But the down side is, if you can't reproduce the primaries, you can't reproduce the color; you can only model it.

I'm not sure how HDR monitors work. But if they only use three primaries, they simply can't reproduce all the colors. As the Hunt quote says, "The difficulty cannot be avoided, because it stems from the basic nature of human colour vision"

No doubt we will find technology that moves beyond this. You could easily reproduced ALL colors on a monitor if you could produce spectral primaries on the fly and not depend on tristimulus reproduction. There are even some old technologies like the Lippmann method that don't depend on three color reproduction that do span the whole gamut. (The Lippmann method is really interesting, though impractical. Worth googling when you have some time)

As far as camera go, Andrew is probably a much better person to ask. I'm really not sure if it's proper to think of camera sensors and raw data as RGB. One of these days I plan on learning a bit about the physics behind camera sensors, but I haven't yet.
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Iliah

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #490 on: January 07, 2011, 08:08:40 pm »

Actually, I'm not missing anything.

I'm sure there will be new models to map and describe the world of reflected light on recorded media

But you are missing. Reflected light is an old part of the game.
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Graystar

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #491 on: January 07, 2011, 08:10:01 pm »

I don't know what you mean. Change a thing about what?

He means that it does not change a thing that you know what you're talking about.

The question was an attempt to discredit you.
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tgray

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #492 on: January 07, 2011, 08:19:45 pm »

So when using these ICC profiles in any current application, when and how (and why) would a conversion take place without adaptation?

I'm not knowledgeable enough in color science to answer that question.  I think the how is probably easy, but the why I am unclear on.

Quote from: Graystar
Right.  And what he's failing to realize is that those cases have no meaning whatsoever

Again, I'm not knowledgeable enough in color science to answer that question.  I'm guessing though that, "those cases have no meaning whatsoever" is not true.  It's probably safer to say that, "those cases have no meaning in most practical usage scenarios."  That doesn't mean that it's not interesting and perhaps even relevant to think about.

And again, for everyone who is saying, "It's just numbers," needs to relax.  This whole discussion is based on science that was probably dismissed as 'just numbers' while it was originally researched, yet here we are, putting it to real world use.  If you don't find the discussion relevant to your real world uses at the current time, just ignore it.
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digitaldog

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #493 on: January 07, 2011, 08:22:26 pm »

Probably need another post but...

Here’s my copy and paste with respect to cameras based on a number of conversations with Eric Walowit and Jack Holms, both on the ICC digital photo group.


Digital cameras don't have a gamut, but rather a color mixing function. Basically, a color mixing function is a mathematical representation of a measured color as a function of the three standard monochromatic RGB primaries needed to duplicate a monochromatic observed color at its measured wavelength. Cameras don’t have primaries, they have spectral sensitivities, and the difference is important because a camera can capture all sorts of different primaries. Two different primaries may be captured as the same values by a camera, and the same primary may be captured as two different values by a camera (if the spectral power distributions of the primaries are different). A camera has colors it can capture and encode as unique values compared to others, that are imaginary (not visible) to us. They don't exist and therefor are not colors. There are colors we can see, but the camera can't capture that are imaginary to it. Most of the colors the camera can see we can see as well. Yet some cameras can “see colors“ outside the spectral locus but usually every attempt is made to filter those out. More important is the fact that cameras “see colors“ inside the spectral locus differently than humans.

The point is that if you think of camera primaries you can come to many incorrect conclusions because cameras capture spectrally. On the other had, displays create colors using primaries. Primaries are defined colorimetrically so any color space defined using primaries is colorimetric. Native (raw) camera color spaces are almost never colorimetric, and therefore cannot be defined using primaries. Therefore, the measured pixel values don't even produce a gamut until they're mapped into a particular RGB space. Before then, *all* colors are (by definition) possible.

Raw image data is in some native camera color space, but it is not a colorimetric color space, and has no single “correct” relationship to colorimetry. The same thing could be said about a color film negative.
Someone has to make a choice of how to convert values in non-colorimetric color spaces to colorimetric ones. There are better and worse choices, but no single correct conversion (unless the “scene” you are photographing has only three independent colorants, like with film scanning).

Do raw files have a color space? Fundamentally, they do, but we may not know what that color space is. The image was recorded through a set of camera spectral sensitivities which defines the intrinsic colorimetric characteristics of the image. An simplistic way to think of this is that the image was recorded through a set of "primaries" and these primaries define the color space of the image.



If we had spectral sensitivities for the camera, that would make the job of mapping to XYZ better and easier, but we'd still have decisions on what to do with the colors the camera encodes, that are imaginary to us.
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digitaldog

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #494 on: January 07, 2011, 08:25:27 pm »

I'm not knowledgeable enough in color science to answer that question.  I think the how is probably easy, but the why I am unclear on.

The question was less directed towards color science and more towards implementation in current products or tools that use these profiles. Its one thing to enter numeric values in web based color calculator or go about making graphs that purposely ignore the adaptation. But can we do this in the current tools we use to convert color spaces using these profiles? If not, there’s probably a reason why.
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Iliah

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #495 on: January 07, 2011, 08:32:19 pm »

> I don't know what you mean.

Can you look at monochromatic light sources and come up with wavelengths that allow for separate responses of L, M, and S?
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MarkM

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #496 on: January 07, 2011, 08:32:50 pm »

Quote
Here’s my copy and paste with respect to cameras based on a number of conversations with Eric Walowit and Jack Holms, both on the ICC digital photo group.

Whoa, I wasn't expecting so much. Thanks! I'm walking out the door, but I'll see if I can wrap my head around the when I'm back home.
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Iliah

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #497 on: January 07, 2011, 08:36:39 pm »

> There are colors we can see, but the camera can't capture

"Can't capture" is not an exect term here. It is akin to saying "There are brightnesses we can see, but the camera can't capture those"
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Iliah

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #498 on: January 07, 2011, 08:42:15 pm »

> wasn't expecting so much.
You must be joking.
It was very, very basic, and it needs some rephrasing for accuracy.
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Manuel_A

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Re: attention color whizes: non-typical sRGB/RGB/ProPhoto question
« Reply #499 on: January 07, 2011, 08:46:15 pm »

Probably need another post but...

Here’s my copy and paste with respect to cameras based on a number of conversations with Eric Walowit and Jack Holms, both on the ICC digital photo group.


Digital cameras don't have a gamut, but rather a color mixing function. Basically, a color mixing function is a mathematical representation of a measured color as a function of the three standard monochromatic RGB primaries needed to duplicate a monochromatic observed color at its measured wavelength. Cameras don’t have primaries, they have spectral sensitivities, and the difference is important because a camera can capture all sorts of different primaries. Two different primaries may be captured as the same values by a camera, and the same primary may be captured as two different values by a camera (if the spectral power distributions of the primaries are different). A camera has colors it can capture and encode as unique values compared to others, that are imaginary (not visible) to us. They don't exist and therefor are not colors. There are colors we can see, but the camera can't capture that are imaginary to it. Most of the colors the camera can see we can see as well. Yet some cameras can “see colors“ outside the spectral locus but usually every attempt is made to filter those out. More important is the fact that cameras “see colors“ inside the spectral locus differently than humans.

The point is that if you think of camera primaries you can come to many incorrect conclusions because cameras capture spectrally. On the other had, displays create colors using primaries. Primaries are defined colorimetrically so any color space defined using primaries is colorimetric. Native (raw) camera color spaces are almost never colorimetric, and therefore cannot be defined using primaries. Therefore, the measured pixel values don't even produce a gamut until they're mapped into a particular RGB space. Before then, *all* colors are (by definition) possible.

Raw image data is in some native camera color space, but it is not a colorimetric color space, and has no single “correct” relationship to colorimetry. The same thing could be said about a color film negative.
Someone has to make a choice of how to convert values in non-colorimetric color spaces to colorimetric ones. There are better and worse choices, but no single correct conversion (unless the “scene” you are photographing has only three independent colorants, like with film scanning).

Do raw files have a color space? Fundamentally, they do, but we may not know what that color space is. The image was recorded through a set of camera spectral sensitivities which defines the intrinsic colorimetric characteristics of the image. An simplistic way to think of this is that the image was recorded through a set of "primaries" and these primaries define the color space of the image.



If we had spectral sensitivities for the camera, that would make the job of mapping to XYZ better and easier, but we'd still have decisions on what to do with the colors the camera encodes, that are imaginary to us.



Exactly ….

Joofa, you need to give the name and phone number of the girl to digitaldog he is correct…

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