Warnings
Once you have configured Photoshop for the proper colour settings, you also need to set up and understand the various warning messages that will be displayed as you open work with your images.
Gamut Warning Preferences
To produce the best prints, it is important that all of the colours present in your image can be reproduced with the particular output method you'll be using. The Gamut Warning option in Photoshop allows you to determine which colours in the image can't printed, based on whether the colours are available in a particular profile.
The Gamut Warning options are actually the only settings in the Preferences dialog in Photoshop that directly relate to colour management. All other settings in Preferences are largely a matter of your personal preference, and don't affect your colour-managed workflow.
You can access the Gamut Warning preferences (see figure left) by selecting Edit > Preferences > Transparency & Gamut (Photoshop > Preferences > Transparency & Gamut on Macintosh OS X) from the menu. In the Gamut Warning section, you can select the colour and opacity of the gamut warning display on your images. To change colour, click the box labelled Color. This will bring up the Colour Picker, where you select the colour to be used. My recommendation is to use a highly saturated colour that is not likely to appear in your images. Keep in mind that you can always return to Preferences dialog box to change the setting if the colour you normally use actually exists in an image with which you are working. I usually use a highly saturated magenta colour, but any colour that will visibly stand out with most of your images is a good choice. You can also adjust the opacity of the colour by changing the value on the Opacity slider. This allows you to use a partially transparent colour for the gamut warning, so you can still see the details of your image under the warning colour. My preference is to keep the Opacity at 100 percent, so that the gamut warning colour stands out more.
Embedded Profile Mismatch
As mentioned earlier, the Colour Management Policies options available to you in the Colour Settings dialog box (see figure right) simply determine the default behaviour. If you work with images from a single source, such as a digital camera, you may want to have the same action take place with every image you open. For example, a digital camera typically captures an image in the sRGB colour space by default. If your working space is set to Adobe RGB (1998), Photoshop will recognize that the profile does not match your working space.
The Colour Management Policies will determine what Photoshop does by default with your image. If you always want the same action performed, you can simply clear the check from the Profile Mismatches option for both Ask When Opening and Ask When Pasting. If these checkboxes are not checked, then the Colour Management Policies option you select will be performed on every image without giving you the option to intervene. This may be fine if you want all of your images to be handled the same way. However, the problem with turning off these warnings is that you won't be warned about possible exceptions with certain images that you might want to handle with a different policy.
If you work with images from a variety of different sources, or if you want to be sure that you don't forget to change the default behaviour in certain situations, then it is a good idea to check the boxes under Profile Mismatches. If the Ask When Opening box is checked, Photoshop will alert you if the profile in the image does not match the working space when you open an image. It will then give you three options, which are the same as the options available for Colour Management Policies:
"Use the embedded profile (instead of the working space)" is the same as Preserve Embedded Profiles. This will cause your image to be converted to the working space, preserving the appearance of the colours in your image to the extent possible. If you save the image, it will still be tagged with the original profile embedded in the image when you opened it.
"Convert document's colours to the working space" is the same as Convert To Working. This will cause the image to be converted to your working space. If you save the image, the current working space that the image was converted to will be embedded as the profile for the image.
"Discard the embedded profile (don't colour manage)" is the same as Off. This will cause the profile to be ignored, and the colour values in the image will be interpreted based on the current working space. This does not produce an accurate display of the image and, therefore, I don't recommend using this option. If you save an image after opening it with this setting, it will not have a profile embedded.
The default option in the Profile Mismatch dialog box will be the option you selected under the Colour Management Policies in the Color Settings dialog box. However, you then have the option to change the default behaviour before proceeding. If you generally convert to the working space, but you have now received an image that is tagged with a custom profile, this gives you the option to change the default behaviour on a per image basis. It also gives you a better understanding of what is being done to images.
For more detail on how these options work, turn back to the earlier section “Colour Management Policies."
Paste Profile Mismatch
Opening an image isn't the only time that a profile mismatch can occur. If you copyand-paste or drag-and-drop pixels from one image to another with different profiles, you must deal with the profile mismatch. If you have checked the Ask When Pasting for Profile Mismatches in Colour Settings, then you will be prompted with the Profile Mismatch dialog box (see figure left) when you copy pixels from one image to another with profiles that don't match. If the box is not checked, then the action selected under Colour Management Policies in Colour Settings will be performed automatically.
Two options are available to you in the Paste Profile Mismatch dialog box.The option to "Convert (preserve colour appearance)" is the one you'll most often want to select. This will change the colour numbers in the image using a profile-to-profile conversion so that the visual appearance of the colours is unchanged, although out-of-gamut colours will need to be changed to the nearest match defined by the rendering intent set in Colour Settings.
The option to "Don't convert (preserve colour numbers)" will cause the colour numbers for the source pixels to be retained and then interpreted based on the profile of the destination image. For photographic images, this isn't generally an option you would want to choose, because it will actually change the appearance of the colours in the image you are copying.
Note: If you copy pixels between two images with different colour modes (such as pasting from an RGB document to a CMYK document), the only option is to preserve colour appearance, so you won't see the Paste Profile Mismatch dialog.
Missing Profile
The Missing Profile dialog box (see figure right) is very similar to the Embedded Profile Mismatch dialog box, except that it appears when the image you have opened does contain a profile. It will be displayed only if you have checked the box for "Ask When Opening" associated with the Missing Profile option in Colour Settings.
As with the Embedded Profile Mismatch dialog box, you have three options from which to choose. The default action will be based on the option selected in Colour Settings.
The option to Leave As It Is (Don't Colour Manage) is similar to the Discard The Embedded Profile option in the Embedded Profile Mismatch dialog box. If you select this option, the image will be interpreted based on the currently selected Working Space in Colour Settings. When you save the image, no profile will be embedded. This is generally not a good choice, as it doesn't include an indication of how the colours in image should be interpreted.
The Assign Working RGB option (assuming an RGB image) provides an indication of what the current Working RGB colour space is based on the setting in Colour Settings. Because the image does not contain an embedded profile, there is no basis for interpreting the colours in the image. If you select this option, the colour numbers in the will be interpreted based on the Working Space defined in Colour Settings. When you save the image, the Working Space that was used to interpret the image when it opened will be embedded in the image, so it will now be tagged with a profile.
The Assign Profile option allows you to assign a profile to the image to determine how the colour numbers should be interpreted. This option is most frequently used assign a custom profile to a film scan or digital capture. By assigning a custom profile to those images, the colour numbers are interpreted based on the profile, which should result in more accurate colours in the image. If you do select this option, a checkbox will also be enabled that allows you to convert to the Working Space defined in Colour Settings after the profile has been assigned, and I recommend checking this box unless you have a reason not to convert your image to the working RGB colour space.
This is the best option in most situations, unless you know under what profile colour values in the image were originally defined. By choosing Assign Profile, you can scroll through all of the profiles available on your computer to find the one that offers the most accurate interpretation of the colours in the image. For example, if you open an image taken with a digital camera with no profile embedded, you can find the best profile to assign that will provide the most accurate colours in the image.
Embedded Profile Mismatch Alert
If you have not checked the boxes to Ask When Opening for profile mismatches, Photoshop
will offer an alert to let you know what is happening with your image (see figure left). This alert is simply warning you that the profile embedded in the image you have opened does not match the working profile. It also lets you know what action will be taken, which will be based on the settings you have set in the Colour Settings dialog box. Since you set appropriate settings in Colour Settings to determine what action should be taken in the event of a profile mismatch, this dialog box is not generally useful. You can click the checkbox for Don't Show Again so that this dialog box will not be shown the future.
Note that if you disable this alert message, but later decide you'd like to receive the alert, the only way to bring it back is to enable all alerts by clicking the Reset All Warning Dialogs button in the Preferences dialog box (Edit > Preferences > General).
Assigning and Converting Profiles
Besides the options available in Colour Settings and with the Embedded Profile Mismatch and Missing Profile dialog boxes, you can also deal with profiles "manually," assigning them to an image or converting an image from one profile to another.
Assign Profile
The Assign Profile command (Edit > Assign Profile) allows you to assign a profile to an image. When you do so, the colour numbers in the image are not changed. Rather, they are interpreted based on the profile you assign (see figure right). Normally you want to preserve the colour appearance in an image, so at first glance the option to assign a profile to an image may not sound like something you would want to do.
However, there are situations where this would be used. The two most common are for assigning a custom profile to a film scan or digital capture. Most scanning software and digital cameras don't allow you to use a custom profile at the time of scan or capture. If you are going to use a custom profile, you'll generally have to assign it after the fact in Photoshop. The Assign Profile command allows you to do this.
Convert to Profile
The Convert To Profile command (Edit > Convert To Profile) allows you to convert an image to a different profile. There are a variety of situations where you may want to convert an image to a different profile, such as when preparing it for a different output method. Each profile causes the colour numbers in the image to be interpreted in a unique way. Converting from one profile to another involves changing the colour numbers in the image so that the colours appear the same after being converted. The results are generally quite accurate, with no visible difference between the image before and after conversion. However, if there are significant out-of-gamut colours, the conversion will need to adjust those values based on the rendering intent selected..