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

[tho_mas]

Let's have an image in Adobe RGB in Photoshop, let's assume that we want to appear it "cooler". One option is to convert to ProPhoto RGB, Intent: Absolute Colorimetric, Engine: Microsoft ICM (or Apple's CMM).

or even "AdobeCMM" (see above)

[Iliah]

> In any case it is possible to preserve all the colors your camera can capture in one color space.

To map would be a better term, but that implies we need to define that colour space and mapping method.

[tho_mas]

In any case it is possible to preserve all the colors your camera can capture in one color space.

To map would be a better term

true

but that implies we need to define that colour space and mapping method.

and what's the issue here?
In how far do you feel limited with regard to the tools available?

[Schewe]

I am not an expert on commercially available CMMs. But, what I hear from more knowledgeable posters in this thread is that they like to do a chromatic adaption from D65 to D50, perhaps using a linear matrix like Bradford transform.

Uh huh...so for the purposes of transforming an image currently in Adobe RGB (1998) to ProPhoto RGB, ALL of the colors within Adobe RGB (1998) will get mapped to, and fit within, ProPhoto RGB without any clipping?

[Iliah]

> and what's the issue here?

Take a shot of something like Time Square in the evening and try comparing the result with what you've seen on the scene.

[tho_mas]

> and what's the issue here?

Take a shot of something like Time Square in the evening and try comparing the result with what you've seen on the scene.

how did you solve the problem with film back then?

[jbrembat]

Well, you do not understand that the better model of the situation is: several colour spaces coexist in the same scene. It is nearly always the case. So, your suggestion to convert is not the correct method to preserve appearance.

You are trying to mix other arguments.
We are speaking if a color (blue AdobeRGB 1998) may be represented in ProPhoto gamut.
You said it cannot be represented.
You are wrong.

In a real scene you can have several illuminants, not several color spaces.
Another time you are wrong.

Jacopo

[digitaldog]

Let's have an image in Adobe RGB in Photoshop, let's assume that we want to appear it "cooler".
One option is to convert to ProPhoto RGB, Intent: Absolute Colorimetric, Engine: Microsoft ICM (or Apple's CMM).

Let me get this straight, we are in Photoshop, we want to make the image cooler, we skip curves, color balance, all the tools for making the image cooler, but we convert the color space instead? And we are on a Mac and don’t have MS ICM (or Windows and Apples CMM). This is a useful (the best) real world scenario for making the image cooler or for using a process (converting a color space) who’s role isn’t color alteration? Bit of a stretch if you ask me.

[Iliah]

>Another time you are wrong.

Good answer when you can't find a better one

[Iliah]

how did you solve the problem with film back then?

Several ways, but mostly shooting black and white, or, when in colour, looking for shallow DoF and composing shots in a way that vivid colours are blurred.

[jbrembat]

Good answer when you can't find a better one

This is what you do when you are not able to answer.
I said:
In a real scene you can have several illuminants, not several color spaces
But I suppose you are so confused that you didn't understand.

Jacopo

[tho_mas]

Several ways, but mostly shooting black and white, or, when in colour, looking for shallow DoF and composing shots in a way that vivid colours are blurred.

I like the black & white version... solves almost all the issues with multiple white points :-)
Seriously... you can shoot a sunlit scene late afternoon with high saturated warm tones and at the same time you get high saturated blue shadows (at ~ 10.000K or what). If you don't like the blue shadows just correct them selectively. If you love them, you can push saturation even further. Finally you could as well process the same file with different white points and merge them in Photoshop.
Seems to be somewhat easier then composing multiple shots.

[bjanes]

Let's have an image in Adobe RGB in Photoshop, let's assume that we want to appear it "cooler".
One option is to convert to ProPhoto RGB, Intent: Absolute Colorimetric, Engine: Microsoft ICM (or Apple's CMM).
--

Peter,

That is an interesting proposition, but we usually do not want the colors to shift and use relative colorimetric. As we have found out, Adobe CMM does not perform absolute colorimetric conversion with matrix based profiles. That option should be grayed out on the drop down menu, as should the option of perceptual rendering between matrix spaces which do not have the necessary look up tables.

My original challenge to Joofa was to show me a color in Adobe RGB which can not be represented in ProPhotoRGB. This is not possible in Photoshop with the Adobe CMM, but can be done with the absolute colorimetric intent in the Microsoft CMM.

An interesting project is to create a Joofa color space with the primaries of Adobe RGB and a D50 white point as shown on the screen capture below. One can then fill the image with RGB 0,0,255 and then convert to ProPhotoRGB. The resultant RGB is 237. Since there is no change in white point, chromatic adaption is not necessary. I presume that the primaries of the Joofa space are interpreted differently for a white point of D50.

The only apparent advantage of the Joffa space is that no chromatic adaption is needed for spaces with a D50 white point. Indeed, when Bruce Lindbloom designed BetaRGB he chose a D50 white point:

"Since Adobe Photoshop and the ICC profile specifications both use D50 as a reference white, this was the logical choice. If instead, a non-D50 white was chosen, then both the creation of, and the use of the working space would require adaptation, which opens the door just a crack for mistakes to be made. Specifying the working space directly in D50 avoids this possibility for error."

Your comments?

Regards,

Bill

[Iliah]

> This is what you do when you are not able to answer.

Are you talking to yourself?

> In a real scene you can have several illuminants, not several color spaces

So, AdobeRGB is defined independent of the illuminant? Funny where it took you.

[Iliah]

> you could as well process the same file with different white points

Better to convert using a proper mixture of absolute, relative, and perceptual intents.

[tho_mas]

> you could as well process the same file with different white points

Better to convert using a proper mixture of absolute, relative, and perceptual intents.

this workflow sounds quite cumbersome.
I always leave my files in the so called "camera profile" of Capture One. These are linearized, Gamma 1.8 coded colour spaces based on charaterization data of the respective cameras; tweaked to create a certain "look" but still based on charaterization data.
I can modify my "camera profile" in any fashion I'd like to... selectively.
So no need to mix different RI's... just edit the files so that they look "good" (or "correct" if this is what you want to achieve).

As we have found out, Adobe CMM does not perform absolute colorimetric conversion with matrix based profiles.

"ACE" does not.
"AdobeCMM" does -> http://www.adobe.com/support/downloads/detail.jsp?ftpID=3618

[Iliah]

> this workflow sounds quite cumbersome.

Actually not if the converter allows to select and set several different white balance zones.

[tho_mas]

> this workflow sounds quite cumbersome.

Actually not if the converter allows to select and set several different white balance zones.

ah, okay... I get it.
In C1 I just select my "camera profiles" (daylight, outdoor daylight, flash, tungsten...) and those provide the required "colour sensitivity" (and gamut) for the respective lighting conditions. Doesn't necessarily mean the image always looks great by default ... but it's quite easy to edit the files accordingly.

[jbrembat]

You wrote:

Well, you do not understand that the better model of the situation is: several colour spaces coexist in the same scene.

I wrote:

In a real scene you can have several illuminants, not several color spaces.

You wrote:

So, AdobeRGB is defined independent of the illuminant? Funny where it took you.

Where is my reference to AdobeRGB?

A real scene illuminant color has nothing to do with color space reference white.

You are trying to switch the argument to white balance, but unfortunately you are weak on that argument too.

Jacopo

[Iliah]

You need to start from the basics. White balance is the form of chromatic adaptation.