Color Managment Question -Photoshop CS2 and Win XP.

You need some better understanding of color management and how to use it than you can get in a reply on this news group.
This may be a good place to start http://www.xritephoto.com/classroom/

IrfanView sounds like it’s not color managed, so it, in effect, uses your monitor calibration by default. If you load your monitor profile as your Photoshop RGB working space, both programs will display identcally. The differences you see are do to the difference between your actual monitor calibration and sRGB – the further apart the two are, the greater the difference you will see.

Yes, Peter, Irfanview is not color managed and does use my monitors calibration by default. Thats why i use it im my comparison. And it is futher correct that when loading my monitors profile in photoshop, both photoshop and irfanview display the same.

My main point is toward your last sentence " The differences you see are do to the difference between your actual monitor calibration and sRGB ".
That last sentence would make perfect sense eccept that my monitors calabiration NEVER changes no matter which profile is loaded in windows. whether is a sRGB profile, or my monitors profile, my desktop (and irfanview for that matter) ALWAYS stays the same. It is PHOTOSHOP that changes. Why would photoshop display sRGB differently if my monitor does not?

No, the monitor calibration doesn’t change, but the profile through which Photoshop is displaying your images does.

Let me try a different explanation. sRGB is a color space that is defined by specific red, green and blue primaries (defining the gamut of the space), a white point (6500K) and a gamma curve (2.2). sRGB doesn’t, however, describe any particular device. It is a mathematecal construct. You monitor, after you calibrate and profile it, has certain characteristics – gamma, white point, etc, which are described by the profile. The further your monitor calibration is away from the mathematical construct of sRGB, the more difference you’ll see. Usually, simply calibrating your monitor to 6500K, Gamma 2.2 is close enough to sRGB that there is very little difference between the two. In your case, that may not be so.

Because Photoshop is color managed, it uses the monitor profile to compensate for exactly how your monitor is calibrated. If you swap out that profile without changing the calibration, it doesn’t change the calibration, but it does change what Photoshop "thinks" it is getting.

Thank you for your answer Peter. It is very well written and helps allot. I am still learning this stuff and will prob read what you wrote over and over while still doing my own tests, but again i thank you.

Actually, your response mirrors something else i read while looking through the tuturials on this site. It was a tuturial for using Adobe Gamma ( the monitor calabirator). It was just one sentence at the very end of the page that struck me. It read…."Monitor compensation is always on and cannot be turned off in Photoshop 6.x."…..that got me thinking that photoshop will always be adjusting the image to compenstate for my monitors limitations.

Going back to your answer again you state that a sRGB color space is just a mathmatical consturct. Now i can see how that would be considered "device independent".

Thanks again.

If you go to the Microsoft Web Site you can download a Color Control Panel Applet that will let you see the differences between profiles. Including those that you create with the Adobe Gamma Control.

< http://www.microsoft.com/downloads/details.aspx?FamilyID=1e3 3dca0-7721-43ca-9174-7f8d429fbb9e&displaylang=en>

Colin

This color stuff can be quite abstract when you’re trying to figure it out, but eventually it will snap into place and all make sense. I remember the first time someone mentioned the work "profile" to me, back in the days of PS 4, and it made me hurt. I’d say that it took a good couple of years of reading and trying to put it all in perspective before I was half-way comfortable with the concepts. The great thing about this is that it never ends. There is always more to learn.

Yeah, i think im going to be at this for a while. Whether im reading web pages, books, or going through forums. Shoot, the whole time at work the other day, all i could think about was profiles.

Just recently i thought out this scenario and wrote it out on paper. The scenario was based on your quote "it doesn’t change the calibration, but it does change what Photoshop "thinks" it is getting". I hope im going in the right direction with the following…..

Lets say you have your monitor calabirated a certain way and then load an icc profile in windows that does’nt match it. For example, you’re monitor is calabirated to match sRGB almost perfectly, but you accidently load a CMYK in windows. Now based on that example, would photoshop get "tricked" by the icc profile and think you’re monitor is displaying CMYK colors? And therefore treat you’re monitor as if it were CMYK. And then if you opened an embedded sRGB JPEG in photoshop (using a sRGB color space), the program would "compensate" the photo as if my monitor were CMYK. Now, if that happened while my monitor acctually displayed sRGB the whole time, it would seem that photoshop’s compensatoin would look off.

wrote:

Yeah, i think im going to be at this for a while. Whether im reading web pages, books, or going through forums. Shoot, the whole time at work the other day, all i could think about was profiles.
Just recently i thought out this scenario and wrote it out on paper. The scenario was based on your quote "it doesn’t change the calibration, but it does change what Photoshop "thinks" it is getting". I hope im going in the right direction with the following…..

Lets say you have your monitor calabirated a certain way and then load an icc profile in windows that does’nt match it. For example, you’re monitor is calabirated to match sRGB almost perfectly, but you accidently load a CMYK in windows. Now based on that example, would photoshop get "tricked" by the icc profile and think you’re monitor is displaying CMYK colors? And therefore treat you’re monitor as if it were CMYK. And then if you opened an embedded sRGB JPEG in photoshop (using a sRGB color space), the program would "compensate" the photo as if my monitor were CMYK. Now, if that happened while my monitor acctually displayed sRGB the whole time, it would seem that photoshop’s compensatoin would look off.

Your eyes play a part in this too.

Windows loads your calibrated monitor settings. So, Windows now has a definition for that. You edit in Photoshop to get the colors just the way you want. Make sure you have a color space attached to the file. Windows or any calibrated device with a profile will be able to translate from what you did to what that device can handle.

Photoshop assumes that the colors you are working from are correct. Based on that and the color space profile (AdobeRGB, sRGB) it is telling the world that this file is based on the standard color management scheme.

If you give this file to someone else – say running OS X and an Epson printer – that Photoshop will see the attached color definition. It will know to translate from that definition to the definition of the Epson/paper it is using.

In summary…

1. Monitor color is defined.

2. Editor’s eyes make the picture what he wants it to look like.

3. Color space (definition) is attached to the file to tell what range of colors were used.

The above 3 steps create a standardized system for defining color in your file.

Any other device using your file…

1. Profile-aware application opens up your file.

2. It reads your attached profile.

3. If that monitor is calibrated, it should look like it did on yours.

4. He prints. The printer driver and color management system on his computer translates your color definition to the one defined by his profile for his printer and his paper used.

The color will be as good as possible.

All of this is based on the assumption that those color definitions have all been correctly done. It assumes that both monitors were calibrated correctly. It assumes that other parties are using the right/best profiles for there printer/paper.

Here’s the key to your question… If any of those color definitions are NOT correct, all the other steps will give incorrect color. That is because the assumption of correctness has been broken.

So, if you tell Windows to use an incorrect profile for your monitor, the color will change. When you open files that you have edited in the past, the colors won’t look right. If you edit new files with the wrong monitor definition, they will look correct to your eye, but the following color translations will translate from the wrong colors.

In your example, it would look off because your eye would see the colors as wrong and you would edit the file that way. Photoshop does not know what colors are correct. Your editing tells it what is correct. Photoshop (and everything after it) is assuming that you are working from a calibrated monitor.

BTW, the term "profile" is unfortunate in that it is used for two different definitions.

Device profiles define color correctedness. Your monitor profile is a device profile. It defines what standardized colors will look like on your monitor. It is device profiles that are the big assumption in the color management system.

The ICC profile that you attach to your file is a Color Space profile. That defines what range of colors were used in the editing process. Since there is a wide variety of color ranges that could be used, you have to send that definition along with the file. It can’t be assumed. Well, easily any way. It also allows the editor to used whatever color range he wants to.

Sorry for the long epistle.

Clyde

wrote:

..> Lets say you have your monitor calabirated a certain way and then load an icc profile in windows that does’nt match it. For example, you’re monitor is calabirated to match sRGB almost perfectly, but you accidently load a CMYK in windows. Now based on that example, would photoshop get "tricked" by the icc profile and think you’re monitor is displaying CMYK colors? And therefore treat you’re monitor as if it were CMYK. And then if you opened an embedded sRGB JPEG in photoshop (using a sRGB color space), the program would "compensate" the photo as if my monitor were CMYK. Now, if that happened while my monitor acctually displayed sRGB the whole time, it would seem that photoshop’s compensatoin would look off

Think_Think:

It sounds like you are making some progress understanding color management. However from the above you are still stuck with a few misconceptions about monitor calibration, the monitor profile and how it is employed. I hope what follows will help you and others. I offer it with the following caveat: I am not a professional in this field, just an amateur who has struggled like you to digest all the information. If I have made any serious errors I hope the experts will correct me.

Lets begin with the device independent color space. The following uses as an example the RGB color spaces (sRGB, Adobe RGB, etc.), although the same logic applies to CYMK and any other virtual color space.

Each virtual color space is defined by a range (gamut) of colors and each assigns to every color wilthin its gamut a specific code in the form of "Rnnn/Gnnn/Bnnn", where nnn is an integer value in the range 0-255. In every case the code refers to a specific color that can be perceived and identified by the human eye (within the range of all colors that can be distinguished by the human eye). Now a quick calculation shows that such a system can theoretically code for over 16 million colors, far more than can be distinguished by the eye or displayed on any monitor. So it is not surprising that, for example, R123/G188/B098 and R124/G189/B099 may specify the same color as far as the eye can determine.

The Color Space Profile is, in effect, the key to the code. In a color managed system the profile is embedded in the image file. When the file is opened by any program (also implementing color management), the profile allows the program to decode the information in the file, to know exactly what color is assigned to each pixel and, if necessary, to translate that code into whatever alternate color space code is used by the program.

To confuse thing just a bit, you need to be aware that two different RGB color spaces (e.g. sRGB and Adobe RGB) may, and frequently do use a different code to describe the same color. Additionally one may define, and assign a code to colors which are not defined by (not within the gamut of) the other. Whenever a file created in one color space is sent to a destination using a different color space the translation into the destination color space is straightforward as long as the profile is present in the source file. In the case where the destination space cannot display a color coded in the source, an approximation is made. The method by which such an approximation is made is specified in Photoshop (and other editing programs) by the choice of "Rendering Intent", a subject which we can easily skip over here.

Now open an image in Photoshop. Display the information palette and select the color sampler tool (set for a 1 pixel sample). Place the cursor over any point in the image and look at the information palette. There you will see the RGB color code for the pixel directly beneath your cursor. The code is written using the "code book" for whatever RGB working color space is currently in use. Photoshop now has to send that information to your monitor, and what happens along the way determines how your monitor will display that pixel. Enter the role of the monitor profile.

Monitors (or at least video cards) also utilize digitally coded information in the form Rnnn/Gnnn/Bnnn. So if the monitor receives 123/188/098 (a slightly grayish green in Adobe RGB code) it will display some approximation of the intended color. The problem however lies in the fact that when that same code is received by 10 different monitors (even of the same make and model) you will likely get 10 similar but distinguishably different colors. Each monitor has a built in bias in the way it decodes the information it receives. Worse yet, this bias tends to drift over time. It is the function of the monitor profile to correct for this bias. The monitor profile is a device specific profile which is used to translates the device independent color space code to a code specific for a given monitor, thereby allowing the monitor to produce as close an approximation as possible of the intended color. And different monitors, each using its own profile, will produce the same color if the system is color managed.

The prerequisites for this color management are: (1) The the data containing the image information must have an embedded color profile specifying the code in which it was written. (2) The program responsible for forwarding this information to the monitor must have access to the monitor profile. (3) The program must implement color management (i.e. be capable of performing on the fly translation of the file code to the monitor code via the monitor profile). In the absence of any monitor profile, or when the operating program does not implement color management, all that can happen is the "raw" file data are sent on to the monitor and the results are unpredictable (or predictably not what you expect).

There are a variety of means by which monitor profiles can be obtained. The simplest is to use the generic profile provided by the monitor manufacturer. The easiest way to construct a "custom" profile is the software only method, such as Adobe Gamma. And the most sophisticated method involves using a hardware device (colorimeter or photometer) in conjunction with a software program (GreytagMacbeth, et. al.). I can think of no circumstances when it would be even remotely appropriate to use a device independent color space profile such as sRGB for the monitor profile. Nor is it possible to "calibrate your monitor to match sRGB" I hope all of the above makes it clear why this is so. As to example #1 in your original post, I can only guess that using sRGB as your monitor profile when opening an image in Photoshop (also in sRGB) results in no translation being made. In effect it behaves as if no monitor profile were loaded. I also hope this helps to explain why you get the results you have observed when using programs that do not implement color management.

Cheers,
Mike.