Monday, April 30, 2012
Convert To Profile Vs. Assign Profile—04/30/12
How to choose the right Photoshop color management tool
|This Article Features Photo Zoom|
CONVERT TO PROFILE
I tend to make prints from my desktop printer, and when doing so I instruct Photoshop (or the printer) to apply an ICC Profile during the print process to ensure the results look match what I see on screen. When sending files outside of your self-contained digital ecosystem, though—like when you send an image file to a lab to be printed—you need to convert your image files to the appropriate color space for the printer to handle. For instance, I use the ProPhoto RGB color space when editing most of my image files, but my lab prefers sRGB files for printing. If I don't convert my files the lab will do it for me for a fee, but then not only have I incurred an expense but I won't get to see ahead of time how different my image will appear in print after the conversion. To change the profile I use the Convert To Profile command in Photoshop's Edit menu to remap the pixels from one color space to another.
To convert to a new profile, click on the Edit menu and scroll down to Convert To Profile. Click it and the popup window will present you with the Source Space (what the document is currently set to) and the Destination—the profile to which you'd like to convert. Scrolling through this list of all profiles loaded onto your machine will show you, visually, how the image will be altered when converted to the new profile. This is why you use this feature: to see how your image will look when eventually printed (known as "soft proofing"). That way you can make adjustments to the new file to make it print more accurately—or at least more to your own liking.
Conversion Options are where you instruct Photoshop how you'd like it to reorganize the pixels. This is worthy of its own how-to instructional piece, but suffice it to say that the Adobe ACE default setting is a fine way to go. For Rendering Intent you'll likely want to use Relative or Perceptual, and probably never Absolute. Be sure the Preview box is checked and simply toggle between intents to determine which look is preferable. The same goes for Black Point and Dither, though you'll probably prefer leaving them on by default. The Flatten option only appears with layered files, and is simply a timesaver if you'll eventually want a flattened image.
While it sounds like it does pretty much the same thing, Assign Profile actually doesn't work the same as Convert To Profile at all. Whereas Convert changes actual pixels (reinterpreting them to make all the pixels fall within the usable color gamut) the Assign Profile command doesn't alter pixels—it only tells the computer that these pixels belong to that color space. Think of it as a way to identify a profile that should have already been embedded in a file. Assign Profile is for files with no color profile currently attached.
Why would you use Assign Profile in the first place? It's most useful for the pre-press world in which photographers may have sent to publishers image files without any color information to aid in accurate printing. The printer could then assign a profile to an image, and from that point on accurately manage the color through output.
For photographers, if you're working in a correctly color managed workflow there shouldn't be many opportunities to use Assign Profile. This tool is intended for digital image files that don't already have profiles attached and your digital camera and/or RAW processing software should take care of embedding the profile by default. The problem arises when some images—particularly those uploaded for online use—are stripped of their profiles. Try to download and print those images and you just never know what might happen to the color.
If you encounter an image that does not have a profile embedded you can use Assign Profile to assign one. Click the command in the Edit menu, and choose one of three options: Don't Color Manage (which you probably don't want to choose), the current Working Space, or any profile on your machine from the drop-down menu. It is, of course, most effective if you know what profile the image should be to begin with, but if not you can toggle through the various options and watch the preview until you find one that looks best.
This is by no means an exhaustive look at these two tools, but hopefully it will help you better understand that although they sound quite similar, these powerful color space tools do not serve the same function at all. And that can help make your color management even more perfect.