Color Management Policies

If you ever got stuck trying to figure out what those dang "Profile Mismatch" or "Missing Profile" alerts were saying in Photoshop 5, you might appreciate the relative simplicity of the Photoshop CS2 Color Management Policies feature. While the working space definitions allow you to tell Photoshop what colors the various numbers in your images represent, the Policies and Warnings sections of the Color Settings dialog box (see Figure 5-21) do something quite different: They let you tell Photoshop how to use the interpretations of the numbers.

Figure 5-21. Color Management Policies

The policies control how Photoshop handles several aspects of color management. When you open a document with an embedded profile, the policies tell Photoshop to do one of the following.

Use the embedded profile instead of the working space, opening the document as a Tagged document in its own "document space" (which may or may not be the same as the current working space).
Convert the image from the document space represented by the embedded profile to the current working space.
Ignore the profile and treat the document as Untagged (in which case the numbers in the file are interpreted according to the current working space).
Ignore the profile and treat the document as a Tagged document in the working space.

When you create a new document, the policies tell Photoshop to treat it as an Untagged document, or as a Tagged document in the working space.

When you move pixels between documents (by copying and pasting or by dragging), the policies tell Photoshop to move either the numerical values of the pixels or the colors those numerical values represent.

When you save a document, the policies tell Photoshop whether or not to embed the profile currently associated with the document. You can override the policy's setting for profile embedding in the Save As dialog box, but the policy dictates whether the Embed Color Profile checkbox is turned on or off when the dialog box appears.

You can set individual policies for RGB, CMYK, and grayscale images, but the policies themselves behave almost identically in each color mode. The thumbnail characterizations of the three policies are:

Off means "behave like Photoshop 4."
Convert to Working Space means "behave like Photoshop 5."
Preserve Embedded Profiles means "behave sensibly."

If this characterization displays some bias on our part, we admit to it cheerfully. Nevertheless, there are some situations where one of the less-sophisticated policies make sense, as you'll soon see.

Off

The Off choice is somewhat misleadingly named, as there's really no way to turn color management entirely off in Photoshop CS. It is, however, pretty close to the way Photoshop behaved prior to version 5. When you set the policy for a color mode to Off, Photoshop behaves as follows:

When you open a file that contains an embedded profile, Photoshop discards the embedded profile and treats the image as Untagged, unless the embedded profile happens to match the current working space. In that case, the image is treated as a Tagged document in its own document space, which in this case happens to be the same as the working space. If you change the working space in the Color Settings dialog box, all your Untagged images will change, taking on the new working space definition, but the Tagged images keep the old working space definition, now acting as a document space. (If you find this confusing and counterintuitive, you're not alone. We think it would be a lot simpler if Off simply treated all your documents as Untagged.)
When you save the document, no profile is embedded (unless you turn on Embed Profile in the Save As dialog box, in which case the current working space profile is embedded), unless Photoshop is handling the document as a Tagged document because its embedded profile matched the working space that was in effect when it was opened. In that case, the profile that was embedded in the file when it was opened is re-embedded when you save, unless you turn off the Embed Color Profile checkbox in the Save As dialog box (see Figure 5-22).

Figure 5-22. The Embed Color Profile checkbox
When you open a file that has no embedded profile, Photoshop treats it as Untagged. When you save the document, no profile is embedded (unless you turn on Embed Color Profile in the Save As dialog box, in which case the current working space profile is embedded).
When you create a new document, Photoshop treats it as Untagged. When you save the document, no profile is embedded (unless you turn on Embed Color Profile in the Save As dialog box, in which case the current working space profile is embedded).
When you transfer pixels between images in the same color mode by copy and paste or by drag-and-drop, the numerical values get transferred. That means if the two documents are in different color spaces, the colors change even though the numbers are preserved. (If the two images are in different color modesCMYK and RGB, for instancethe color appearance is always preserved.)

Off is the policy you want if you're a dyed-in-the-wool, by-the-numbers type who has been cursing at Adobe for years for stuffing color management down your throat. Of course, you don't have to set all the policies to Off. If you're in an all-CMYK, by-the-numbers workflow, you can set the policy to Off just for CMYK, and still get the benefits of color management in the other spaces. Similarly, if your work is mostly for the Web, and you need Photoshop's RGB to behave the same as RGB in the vast majority of Web browsers, you can set the policy to Off for RGB. (Well, actually, as we noted earlier in the chapter, on the Mac you may also want to set your RGB working space to Monitor RGB to ensure that RGB in Photoshop matches RGB in your other, non-color-managed applications.)

However, if you want to use color management in Photoshop, you'll want to choose one of the other policies and simply untag documents that need to be untagged on a case-by-case basis (see "Assign Profile," later in this chapter).

Preserve Embedded Profiles

This is the third-millennium, industrialstrength color management approach. Preserve Embedded Profiles is the "safe" policy, in that it makes sure Photoshop doesn't do color conversions when you don't want it to. With this policy, the working spaces in Color Settings are there only as a convenience because each image can live in its own document space. On the other hand, it can also be the "dangerous" policy because if you're not at least a little careful, you can wind up editing images in color spaces that are wildly inappropriate for editing. For instance, if your scanner software embeds its own profile in an image, this policy might mean you're editing the image in the scanner's space, which is significantly less than optimal. Overall, though, it's the policy that we typically use.

When you open an image that contains an embedded profile, Photoshop preserves the profile and treats the image as Tagged, using the embedded profile as the document space (which may or may not be the current working space). When you save the document, the document space profile (the profile the image had when you opened it) is once again embedded in the saved file.
When you open an image with no embedded profile, Photoshop treats the image as an Untagged image (it preserves the lack of an embedded profile, if you will). When you save the document, no profile is embedded (unless you turn on Embed Color Profile in the Save As dialog box, in which case the current working space profile is embedded).
When you create a new document, Photoshop treats it as a Tagged document and assigns the current working space profile as the document space. When you save the document, Photoshop embeds the document space profile (even if you change the working space in the Color Settings dialog box, it has no effect on the image, which stays in the document space).
When you transfer pixels between two RGB or two grayscale images (by copy and paste or drag-and-drop), the actual color gets transferred. If the two images are in different color spaces, the numbers change even though the color appearance is preserved.
When you transfer pixels between two CMYK images, the numerical values get transferred. If the two CMYK documents were in different CMYK spaces, the color appearance changes even though the numbers are preserved. While this routine is the reverse of what happens with RGB and grayscale files, it is actually more logical and useful.

We believe quite strongly that Preserve Embedded Profiles is the best policy for the vast majority of Photoshop users. It keeps track of color for you and rarely performs any conversions that aren't explicitly requested (and never does so if you keep the Profile MismatchPaste warning turned on). If you have to deal with files from many different sources, this is almost certainly the policy you want to use. It does a good job of keeping color management out of your face, but it also offers tremendous power and flexibility for hard-core color geeks.

Convert to Working Space

Convert to Working Space tells Photoshop CS to behave very much like Photoshop 5, converting everything into your working RGB, CMYK, or Gray space. It tells Photoshop to convert images from their own space into the current default working space automatically. We find this method a bit too authoritarian, though if your workflow relies on picking a single RGB, CMYK, or grayscale color space and normalizing alll your images into it, you'll almost certainly want to use this policy. But we think it's best thought of as an automation feature: If it does something you wanted done with no intervention, that's great; on the other hand, if it does something unexpected behind your back, it's not so great!

When you open a file that already has the current working space profile embedded, Photoshop preserves the profile and treats the image as a Tagged image, using the embedded profile as the document space. When you save the document, the document space profile (the profile the image had when you opened it) is once again embedded in the saved file, even if you change the working space in the Color Settings dialog box when the image is open.
When you open a file that has an embedded profile different than the current working space, Photoshop converts the image from the embedded profile's space to the current working space. From then on, it treats the image as a Tagged image, with the working space profile that was in effect when it was opened as the document space.
When you open an image with no embedded profile, Photoshop treats the image as Untagged. If you change the working space, Photoshop keeps the numbers in the file unchanged and reinterprets them as belonging to the new working space (so the appearance changes). When you save the document, profile embedding is turned off by default (though you can turn it on in the Save As dialog box).
When you create a new document, Photoshop treats it as a Tagged document in the current working space. If you later change the working space, Photoshop preserves the working space profile that was in effect when the document was created. When you save the document, that same profile is also embedded.
When you transfer pixels between two images (whether it's RGB-to-RGB, RGB-to-CMYK, or whatever), the color appearance gets transferred, even if that means Photoshop changes the numbers (which it'll have to do if the files are in different color spaces).

Convert to Working Space is a useful policy when you need all your images in the same space, such as when you're compositing RGB images or repurposing CMYK images from several different sources for a single output. It's a handy automation feature when you need to convert a bunch of pictures quickly. But unless you're very sure about what you're doing, it's safer to use Preserve Embedded Profiles instead, and perform the conversions manually whenever you need to change an image's working space (see "Applying Profiles Outside Color Settings," later in this chapter).

Profile Warnings

Although they appear in the Color Management Policies section of the Color Settings dialog box, the Missing Profile and Profile Mismatch warnings operate independently from the policies. (You can think of it this way: The policy determines the initial default setting of some of the warnings.) Unless you're adamantly opposed to the use of color management, we suggest you turn all the warning checkboxes on and keep them on until you decide you don't need them. They offer choices, letting you override the default behavior of the policy you've chosen for a specific color mode, though we'd find them even more useful if they didn't demand clairvoyance on our part and let us see the image before making decisions.

Profile Mismatch: Ask When Opening

When Profile Mismatch: Ask When Opening is turned on, Photoshop alerts you when you open a document with an embedded profile that's different from the current working space (see Figure 5-23). Even better, this Embedded Profile Mismatch dialog box offers you three choices for handling the profile mismatch.

Figure 5-23. Embedded Profile Mismatch dialog box

Use the embedded profile (instead of the working space) tells Photoshop to keep the embedded profile, treating the document as a Tagged image in the embedded profile's space. The embedded profile is then used to display the image, and is also used as the source profile for any subsequent color conversion. This is typically what you'd want to do.
Convert document's colors to the working space does what it says: It performs a conversion from the embedded profile's space to the current default working space. This makes sense if you need several images in the same working space (for example, to composite them).
Discard the embedded profile (don't color manage) strips off the embedded profile and opens the document as an Untagged image. The numbers in the document are left unchanged and are interpreted according to the current working space definition. You might use this if you know you're going to significantly edit the color and tone of the image and you don't care about any color interpretations that were already assigned. Similarly, this might be appropriate for an image destined for the Web, especially if you'll be saving it in the sRGB space.

The Embedded Profile Mismatch dialog box chooses one of these three as the default (the one that you'll get if you just hit the Enter key). The default it picks depends on the policy you've chosen for that color mode. Of course, the dialog box always allows you to override the default behavior for the policy on an image-by-image basis.

Profile Mismatch: Ask When Pasting

The second checkbox, Ask When Pasting, comes into play when you move pixels between two images that are in the same color mode, but in different color spaces (like sRGB to AdobeRGB, or from one CMYK setup to another). When this is on, Photoshop asks you whether you want to paste the numerical values or the color appearance (see Figure 5-24). Note that when you copy and paste or drag and drop between images that are in different color modes (like RGB to CMYK), this alert doesn't do anything because Photoshop only lets you paste the color appearance.

Figure 5-24. Paste Profile Mismatch dialog box

Just to be clear: In this dialog box, "Convert (preserve color appearance)" tells Photoshop to change the numbers in the image so that you get roughly the same color. It's like doing a profile-to-profile conversion. We add the caveat "roughly" just in case a color in one profile simply cannot be represented in the gamut of the target profile. The "Don't convert (preserve color numbers)" option simply copies the numbers from the source file into the target file, without worrying about color changes. As with Profile Mismatch: Ask When Opening, the default option (the one you get if you just press Enter) is set to match the current policy for the color mode.

Missing Profile: Ask When Opening

The third warning, Missing Profile: Ask When Opening, comes into play when you open a document with no embedded profile. When this is turned on, Photoshop lets you choose how you want it to interpret the numbers in documents with no embedded profiles (see Figure 5-25).

Figure 5-25. Missing Profile dialog box

Leave as is (don't color manage) tells Photoshop to treat the file as an Untagged document. The numbers in the file are preserved and interpreted according to the current working space (which means that the appearance may change radically).
Assign working space tags the document with the current working space profile. As with the previous option, the numbers in the file are preserved, and interpreted according to the current working space. The difference is that the document is treated as Tagged, so it keeps that profile if you subsequently change the working space.
Assign profile lets you tag the document with a profile other than the working space profile. Again, the numbers in the file are preserved, but in this case they're interpreted according to the profile you choose.
Assign profile and then convert document to working space lets you assign a source profile to the document, and then convert it to the working space. This is the only option of the four that actually changes the numbers in the file.

If you're in a workflow in which you know where images are coming from and you know where they're going, you can probably turn off the warning dialog boxes off. When you don't need them, they do get kind of annoying after a while.