Color Management in Adobe Photoshop® part 5:
The Assign Profile Dialog Box
(And What You Can Do With It)
Since assigning a profile controls how the numbers in an image file are interpreted and does not try to convert them to anything, the Image> Mode> Assign Profile dialog box is much simpler than the convert to profile dialog. You can see it below:
Of the three “radio buttons”, the first control, “Don’t Color Manage This Document” is the most complex because of its misleading label. Photoshop’s color management is so integral to the application at this point that it can’t even display an image on your monitor without using color management. So why pretend that color management can be turned off? Probably because the whole concept is a little scary to some people, or they have seen incorrect color management ruin an image, and they believe that they are better off without it. What happens when this choice is picked is that it actually un-assigns the profile that was being used for interpretation previously and instead uses the default working space for the current color mode (from your Photoshop color settings) to determine color meaning. So if you were already using the mode’s working space, you will not see any difference on the monitor when this button is selected. It also makes the default behavior for the file to have the “Embed Color Profile” box in the “save as” dialog unchecked. You can manually check it, and if you do you will see that the profile that is embedded is your default for the color mode. Since a profile is always assigned to an image for display, and you can un-assign the current profile by assigning another one, and because you can uncheck the embed color profile box yourself if you ever needed to, I can’t think of a single use for the don’t color manage button.
The next two buttons are pretty straightforward. “Working (color mode name):” assigns the modes default working space from color settings, just like don’t color manage. The only difference is that this option does not automatically change the default behavior of the save as dialog. If the file was saved without embedding the last time it was saved, it will default to that again. Otherwise, the default will be to check the embed color profile box. Also unlike don’t color manage, this button does have at least one use: you can select it as a shortcut in situations when you want to assign the default working space and you don’t feel like scrolling through all the other choices available in the next button, “Profile”. The profile button allows you to assign any color space or profile for the current document’s color mode. (Since assigning is interpreting the numbers in an image file, you can’t use the numbering system from other color modes.) This is the most useful button, and you can check the preview box to see the effects of assigning various profiles.
How can the assign profile box be used? While it is not as often used as convert to profile, there are some situations where it can be essential. They include:
• Assign an input profile. You could use assign profile to apply an input profile for a digital camera or scanner. Next you would want use convert to profile to convert to a trusted editing color space, such as sRGB, Adobe ’98 or ProPhoto. This is because input profiles are generally not linear along their neutral axis, nor are they uniform in the size of color step represented by a particular value. By definition they try to reflect the inherent non-linearity and non-uniformity of the device. So a neutral grey photographed with a digital camera might not yield equal RGB values (R=G=B) after the camera’s custom profile is assigned. Many Photoshop color controls, including all grey balance samplers, assume that R=G=B is neutral and that a change of color in one region is roughly equivalent to a change elsewhere. To easily use any of these controls, you must first convert to a linear, uniform space. In fact, this is the reason that sRGB, Adobe ’98, ProPhoto, and other spaces like ColorMatch are called “editing” spaces; In a totally color managed workflow, you assign your input device’s custom profile, convert to an editing space for editing and color correction, and finally convert to a printer’s custom profile for output.
• Evaluate the effect of printing or displaying a file on a profiled device without using color management. If you have an accurate profile for a device, you can see how the device would render the file with no color management by assigning its profile to the document. This is most often used in certain printing press situations, specifically when a print shop does not use ICC profiles but instead prints to a “standard” print condition such as SWOP. Traditional web and offset print houses handle color in a variety of ways, and many of them are able to get consistently excellent results with no use of ICC profiles whatsoever. One such method is to print to a standardized print condition. To help those of us who do use ICC profiles, these print conditions are characterized as ICC profiles like U. S. Sheetfed Uncoated, Euroscale Coated, and U.S. Web Coated (SWOP). If the print shop doesn’t use ICC profiles but does print very close to one of the standards, you can get a pretty accurate “soft proof” (a “proof” on your monitor as opposed to a “ hard” paper contract proof) by assigning the profile for the standard.
• Try to “guess” what profile or color space an untagged image was created in. We will discuss embedding profiles as part of the file saving process in the next section of “Using Color Management in Adobe Photoshop”, but we can talk about how to deal with the situation now. If you receive a file that was saved without the previous user embedding it’s profile or color space, you cannot be one hundred percent sure what the color meanings in the file really are. If you are able to ask the user and get an answer, you can assign the profile or color space and you should be okay going forward. In many cases however, a satisfactory answer is unavailable and you are forced to guess at what was used. The assign profile dialog is the best tool for this because it allows you to use the preview button to visually evaluate the effects of interpreting the file using various color spaces on your profiled monitor. This method of trial and error to find the best looking option is far from perfect, and it is entirely possible that the file uses a custom profile that does not exist on your system. Even when common color spaces are used, with many images it can be difficult at best to determine where the color came from.