Untagged files, Color Settings and Convert to Profile questions

Second, what is the function of the Convert to Profile option?  Under Source Space for most of my files is listed Adobe RGB (1998), not sRGB; aren't they different - so isn't that a discrepancy?

By @bartonlew

It’s OK if image files have different profiles. What profile an image has depends on where it came from, and what assigned that profile.

A profile is sort of like a passport. It isn’t expected for everyone on earth have the same passport; the point and the value of a passport (like a profile) is that it tells you how to interpret the person holding it. If three people get off a plane and they show you different passports, you understand that each person might need to be handled differently, like which language to try first when speaking to them.

When three images have different profiles, that tells the OS or app that the color values in each image need to be interpreted in a different way for each image. The OS or app uses the info in each profile to correctly interpret each image’s color values, so that even though each image might have recorded their color values using different color gamuts, each image is appropriately interpreted and appears as expected on screen and when printed.

So the color management system in an OS or app reconciles differences caused by images reproducing colors in different ways, and the way the OS or app understands how to compensate each one is by taking into account the information in the color profile that comes with each image.

When a file is “untagged,” that means no color profile was included with the image. This can be a major problem, because without a color profile, the OS or app has no reference for how the color values are supposed to look. The OS or app (or you) need to make an assumption (a guess) as to what color profile correctly represents how the colors were recorded (“Let’s interpret this as sRGB and see if that looks right.”). If the guess is correct, then the colors look correct.

You use Convert to Profile when an image’s current color space is not what is required. For example, if you received an image in ProPhoto RGB but your client requires sRGB for the final edit to be uploaded to the web, Convert to Profile is one way to make that happen in Photoshop.

You use Assign Profile when you are not converting; instead, an image’s current color profile is wrong or missing and you need to attach the correct profile to the image. In the untagged image example above, you would use Assign to Profile to preview (test) different guesses as to what the profile might be, and when one makes the colors look right, you apply that profile permanently, so the image is no longer untagged.

An analogy for that: Assign Profile is like a uniform; if you put on an airline pilot uniform then people will interpret you as an airline pilot. But that is only a correct interpretation if you really are a airline pilot. If you go through the training and become an airline pilot, that is like Convert to Profile: You were not an airline pilot before, but you really are one now, and the uniform (the profile) describes you correctly to others.