Color Management in Adobe Lightroom
As an application geared toward photographers, it's no wonder that Adobe Lightroom supports color management. Most of how Lightroom handles this is automatic without you needing to do anything. But that's not true for everything.
First, no application can do an adequate job of rendering accurate color unless you are working with a monitor that itself displays color accurately. That means you have to profile your monitor. There's no getting around it. No monitor can render accurate color without this. Creating a profile allows your system to compensate for any color response issues your monitor may have. And while LCD monitors don't tend to change color over time as much as the old CRT monitors did, it is still necessary to periodically re-profile your monitor, if for no other reason than to verify that the color it is showing you are still accurate. Once you know that the colors you see on your monitor display really are the colors found in your image files, you can turn your attention to the applications you use to edit them.
Overall, Lightroom makes color management fairly straightforward. Upon installing the program, Lightroom will already display previews on your monitor using the correct profile. You know, the one you created in the previous paragraph. Lightroom gets the needed information directly from your operating system without the need to ask you about it at all. Unlike in Photoshop, there are no color settings you have to fiddle with.
When working on a raw image in Lightroom, the data in the file are in a linear gamma color space that Lightroom converts on the fly for the on screen preview, much as Adobe Camera Raw does. If you are working on a jpeg, Photoshop PSD, TIFF or similar format file, Lightroom will make use of an embedded color profile if it finds one. Everything is as you'd expect. You don't even need to really think about the fact that this sort of thing is going on behind the scenes in Lightroom since it's all automatic and there are no configuration settings involved. And since you can't actually create new files from scratch in Lightroom as you can in Photoshop, there's no need for a "working space" profile either. On screen conversions are done using the Perceptual rendering intent. Untagged images are rendered assuming sRGB, which will likely be correct for web jpeg images but may not be the right profile for other untagged files. Take this as a lesson that if you care about the colors in anything other than sRGB files, be sure you save them with an embedded profile.
For efficiency, the images in the Library module are rendered using cached thumbnail saved in the Adobe RGB color space. This seems to be a great choice given that a number of current high end monitors are capable of displaying colors beyond the basic sRGB gamut, with some approaching 100% of the Adobe RGB gamut. Keep in mind that regardless of the profile for the thumbnails themselves, what you see on your own monitor will have been converted using your monitor profile and will be therefore limited to its gamut.
When working on raw images, the histogram in the Develop module assumes you will ultimately output your images using a color space with a gamma of 2.2. Lightroom does this to provide more informative histograms that would be the case were it to show you linear gamma values. The 2.2 gamma response curve is what is used by both sRGB and Adobe RGB. This is also the value you should have your monitor display set to, regardless of whether you are using Windows or Mac OS X.
When you export from the Slideshow and Web modules, Lightroom automatically converts all images to sRGB so they stand a fighting chance of looking correct on the majority of people's monitors whether they are profiled or not. The exported images are tagged as sRGB too so if you view them on a color managed system they will render as you would expect.
Where color management settings do come into play in Adobe Lightroom is in the areas of printing and interfacing with external editors and other third party applications.
By default, the Print module in Lightroom has color management set to "Managed by Printer." To change this, click on the profile selector in the Print Job section of the right hand panel and select "Other...." This will allow you to add installed device profiles to the the dropdown list. Check the ones you generally work with and click on "OK." Lightroom starts with just "Managed by Printer" and "Other..." but you can add others using this process and they will show up in the list too. Now you can make use of this dropdown to select the appropriate profile to print with. At first this extra step of adding profiles to the list may seem cumbersome, but you only have to do this to add new profiles not to make use of them. Personally, I like this since I have quite a few profiles installed that I rarely make use of and not having them clutter up the list in the print dialog seems like a great idea. Once you select a profile an option for selecting the Rendering Intent will magically appear immediately below this. Lightroom allows you the choice of only Perceptual or Relative since the Saturation and Absolute Colorimetric intents really have no use for digital imaging. As when printing with application color management in other programs, remember to turn off color management in your print driver to avoid nasty surprises.
Lightroom has no soft proofing capability. Hopefully Adobe will add this in a future release. Please.
When interfacing with external editing programs, Lightroom has to convert the raw image data to something another program can make use of. If you go to Edit >> Preferences >> External Editing you can tell Lightroom how to do this. You can specify the file format, bit depth, and color space. Choices for color space are limited to sRGB, Adobe RGB (1998) and ProPhoto RGB. ProPhoto has the largest gamut of the three so assuming you have also set the bit depth to "16 bits/component" (16 bits per channel) this would be a good color space choice to preserve the greatest amount of color information possible. Note that the choice here for the Resolution setting has no bearing on the actual data sent to an external editor and serves merely to tell the receiving application how to display what it gets. All the same data is there regardless of what resolution you choose. Lightroom gives you separate settings for exporting to Photoshop and an "additional external editor" of your choice.
As I say, overall, Lightroom makes color management fairly straightforward. For those intimidated by the variety and seeming complexity of Photoshop color management settings, this should be a welcome change. For the most part, Adobe has done a good job of getting rid of settings you don't really need and making intelligent choices for you when possible. With the exception of the lack of support for soft proofing, I think they've done an excellent job in this area.