getting to know color management..

[algirdas_kepezinskas]

Hello,

 

i realise that this topic has been beaten to death even on these very forums,

but i've tried reading numerous numerous questions here, with tons of answers,

and i did understand a lot, but am still missing bits and pieces of information

to see full picture of color management in PS/Windows. So sorry if i'm

repeating same questions, but I would really like to know what i'm doing,

instead of just do stuff blindly.

 

Ok, so here it goes.

 

I'm taking my in RAW, sRGB. That I understand - camera saves numbers mapped to

values in sRGB color space. All is fine.

 

My Photoshop working color space is set to sRGB aswell, so no conversion

happens here. And that is fine aswell, i can understand what working color

space is.

 

From what I understand (and that is based on

http://www.microsoft.com/whdc/device/display/color/default.mspx - "sRGB Color

Space Profile. sRGB is the default color space in Windows, based on the IEC

61966-2-1 standard. An sRGB-compliant device does not have to provide a profile

or other support for color management to work well.") all non ICC applications

on Windows including all windows image api's and so on work in sRGB color space

aswell. Still, all is fine.

 

And so far, everything is clear. My image in Photoshop, no matter if i edit,

soft proof in Windows RGB or Monitor RGB, or export it to JPG and load it up in

any app, all look the same - provided i don't assign any ICM profile to

monitor. That all is good. I guess that means that my monitor outputs colors

very close to sRGB by default, without any profile. Otherwise, the image should

look different when in soft proof -> Monitor RGB mode, right?

 

ok, now this is where i'm getting lost. I have an Samsung 193p monitor, and

Samsng released ICM profile for it. While i do understand this is nowhere as

good as good calibrated profile using dedicated tools, this is best i can get,

since huey or spyder or whatever is too expensive for me - at this stage,

anyway.

 

Alright, so I have this ICM profile for monitor. I load it up and assign it to

monitor. And what I expect to happen, is that in Photoshop all the images

should look still the same as they did before, but in soft-proof -> Monitor

RGB, and all windows applications, they should appear a bit different, right?

 

Well, no. What happens is exact reverse. In soft-proof and windows they still

look like they did before, however in all photoshop editing areas, including

ACR import window, they now look different! How so? I can understand this at

all.

 

Furthermore, when someone calibrates monitor, which color space are they

calibrating to? Because, from what i understand, calibration should correct

differences between expected output and actual output in color, but in what

color space?

 

Wheesh, so much text, hope someone can clear it up for me..

[algirdas_kepezinskas]

Ok, after much more experimentation, I think i'm starting to understand how this all wroks.

 

Correct me if I'm wrong, but:

 

In photoshop, image is displayed using Monitors active ICM profile.

 

When I enable soft-proofingm, and select Monitor RGB, image is rendered directly into monitor, skipping any ICM profile, and displaying how it would look on an uncalibrated monitor. If I select Windows-RGB, it displays it rendering something close to sRGB profile. If i create a custom setup using my calibration-generated ICM profile, then it shows how it would appear on this Monitor with that profile in ICM aware application - and that should be exactly the same as what is shown without color proofing. Correct?

[ellis_vener_photography]

"Furthermore, when someone calibrates monitor, which color space are they calibrating to? Because, from what i understand, calibration should correct differences between expected output and actual output in color, but in what color space?"

 

sRGB, Adobe RGB (1998) and Pro Photo, etc. are device independent RGB color spaces. Your monitor is a device so you don't use a color sapce for it, you use a Profile. Profile are device dependent color spaces --they take into account the performance characteristics of that specific device to within the limitations of the device, neutralize the display so that ideally what you see on screen a neutral rendition of your photo.

 

I think your problem was created when you assigned that profile to your monitor. Monitor profiles just live in the background and are used automatically by ICC /ICM aware applications.

[lobalobo]

Although I am hesitant to respond, because Ellis is an expert and I am not, just struggling with this stuff as is the original poster, I thought it might help to give my non-expert interpretation of what Ellis says on the chance my way of thinking about this helps someone else just learning:

 

Think of sRGB and Adobe RGB color space as alternative instructions to a device such as a monitor or a printer. So aim your camera at a reddish-pinkish rose and record the image in RAW (you say you shoot in RAW). To this point, the recorded image does not have a color space associated with it; instead it simply contains the data ready to encode. Now convert the RAW image to a JPEG; to do this you must choose a color space, which here means nothing other than a code so that a monitor or printer asked to interpret the color will, if told to use the same color space, choose the precise shade of red or pink that is chosen on conversion. Matching is important. If, for example, you convert the jpeg using Adobe RGB then display the image on a monitor that expects to see sRGB the image will look washed out (which is no more surprising that getting a poor translation of Spanish into English if the interpreter speaks only Portugese and English). Note that so far, consistent, I hope, with what Ellis says above, I haven't mention a monitor or printer/paper profile. These are independent. As I understand matters, these profiles help the monitor or printer convert whatever color space its instructed to use as accurately as the device is capable (which is not perfectly, by the way). So the best result is from converting your image into a color space, say sRGB, then looking at the image on, say, a high-quality monitor using software that instructs the monitor to translate in sRGB, then display the image on a properly profiled monitor that gives as close as possible to the colors recorded in the sRGB color space. Hope this helps, and I apologize if it is either wrong or so simple-minded that it was already understood. (And I don't intend here to get into the relative merits of Adobe RGB over sRGB; just describing a framework as best I understand it.)

[ellis_vener_photography]

"Think of sRGB and Adobe RGB color space as alternative instructions to a device such as a monitor or a printer. "

 

I am not sure what you meant by that, but I'm pretty sure that isn't what I meant or how I would define or describe device neutral color spaces.

 

"To this point, the recorded image does not have a color space associated with it; instead it simply contains the data ready to encode."

 

Correct, mostly.

 

"Now convert the RAW image to a JPEG; to do this you must choose a color space, which here means nothing other than a code so that a monitor or printer asked to interpret the color will, if told to use the same color space, choose the precise shade of red or pink that is chosen on conversion."

 

Well not exactly. Converting a raw file to a TIFF, PSD or JPEG does involve choosing a color space to define the red, green and blue values of a pixel in a particular color space -- we call them color spaces because once they are assigned numeric values you can map their co-ordinates in a 3 dimension grid in relation to a set scale. Whether that is an "accurate" rendering depends on many things, including the characteristics of the device ( the computer display or if we are talking about prints the device is considered the combination of the printer, paper and (if inkjet) inks or the interaction of the paper's emulsion and photochemistry. the light you view the print in also can affect one's sense of whether or not the rendering is "pleasing".

[steven_clark]

Not all programs automatically assume the monitor to use the Windows monitor profile setting. In fact in my experience Photoshop is pretty much the only program that DOESN'T let you manually set it.

[lobalobo]

Well, once again, I wouldn't argue with Ellis, but I'm not sure where or if he disagrees with

me. And for my own edification, I'd be interested to know if I have anything wrong, so let

me clarify:

 

Point your camera at a pure red rose and snap a RAW image. Will you be able to see a rose

of exactly that color in a print. The answer, I take it, depends on a number of factors.

First, can your monitor display or your printer and paper produce this precise color from

the information it receives from your camera? Second, assuming that the answer to each

part of the first question is "yes" can you properly direct the display and print of this

precise color?

 

Regarding the second question, let's say you display the image of the rose on your

monitor and you use your processing software to get the color pure red (or a satisfactorily

close color) on the screen. And let's assume that the color fits within (i.e., is available in)

either the sRGB color space or the Adobe RGB (or "aRGB") color space and can, in principle,

be reproduced by your printer on your chosen paper. Will you succeed? Again, as I

understand it, this depends on a number of factors.

 

Was your monitor properly calibrated? That is, when you saw a red rose on the screen, did

your processing software "think" it was displaying a red rose. If it thought it was

displaying, say, a purple rose and then you take all the right next steps to get the software

to recreate on paper what you saw on the screen, what you'll get is purple.

 

But now let's assume that the monitor was properly calibrated, so that your processing

software thinks it's displaying a red rose and it is. You now have to save the image to a

format that can be printed, say a JPEG file. You choose the aRGB color space, convert, and

save.

 

Now the printer. You instruct the processing software to print the image. To get the

results you want you need to be sure that the software tells the printer that you are using

the aRGB color space, and you need to be sure that the printer is capable of interpreting

the aRGB color space. Otherwise you will not get the right color. For example, if the

numerical code for "red" in aRGB corresponds to, say "purple" in sRGB--I know it doesn't,

this is just an illustration--and if your printer interprets the file as sRGB it will try to print

a purple rose, not a red one.

 

But let's say that you correctly tell the printer that it will be receiving an aRGB file and so it

will try to print a red rose. And assume that your printer can handle aRGB. Will you

succeed now? Still depends, this time on whether the printer/paper combination is

properly profiled. That is, when this printer using this paper gets instructions that it

interprets to print "red" does it print red accurately or some other color, maybe purple

again. If it is properly profiled, and all the other steps are followed, what you get is a red

rose.

 

This description is not intended to be technically accurate. (I'm incapable of giving a

technically accurate description.) And I don't mean to enter a metaphysical debate about

whether the color in nature can ever be perfectly reproduced on paper, etc. But this

framework for thinking about color management has been helpful to me, despite its

imprecision, and I thought that it might be helpful to the original poster or others who

might conflate color space selection with other aspects of color management, a mistake I

and many other new users have made (sometimes even after reading good color

management texts, which occasionally allow the reader to lose the forest for the trees).

But again, if I don't have this right even in basic principle, I'd be happy to learn more.

[Tim_Lookingbill]

If you need a more simplified explanation of color management, this site <a href="http://

www.cambridgeincolour.com/tutorials.htm">Cambridge In Color Tutorials</a>

should clear things up for you.

</p>

 

<p>

Just scroll down to the CM section. This is a very complicated subject and the lengths of

your posts indicate you need some sort of primer to get a more overall understanding of

what's going on.

[emre]

When you calibrate your monitor, you specify a correlated color temperature and a tone response curve (gamma). The job of the profiling software is to find the biggest color space for your particular monitor that fits those parameters.

[lobalobo]

Yeah, I've read the more complete and more precise accounts of color management. My attempt was to provide an admittedly stylized account of the basic steps of color management, one that helped me get a handle on the more complicated explanations. (Even the "simplified explanation" that Tim recommends, after starting with a metaphor to spiciness, soon provides a three dimensional representation of sample color space and the same space rotated 180 degrees; this does not strike me as simple, at least not as simple as the level at which I was aiming.) So sure, I know that "color" includes both hue and saturation and many other things that I ignored, but I was simply trying to provide a starting point that was helpful to me and I thought might be helpful to others, beginner to other beginners. (It is my experience that students sometimes can explain to other students more easily than can an experienced teacher, as the students may understand better what confuses other students.) But what I am getting back is that my accounts are incomplete and not entirely accurate, things I knew when I posted and said so. Sorry to have wasted anyone's time.