I’m now in the process of trying to figure out how to color calibrate across my dual 17″ LCDs. We have a ColorVision Spyder Pro (supports CRTs -and- LCDs) and both monitors have been run through the “standard” (rather than “precision”) calibration mode… at night… with no ambient light (including any other monitors) in the room during calibration.
And yet, my new LCD (which sits directly in front of me) has a noticably greenish color cast — most noticable when I let a window or photo span across both monitors — and my original 17″ LCD (which sits directly beside the primary, slightly angled a few degrees towards me) is slightly darker/higher contrast in appearance. To further complicate the situation, whites on my primary (new) LCD seem pure/white-er, while the secondary has a faint reddish color cast imbued to its white. This all holds true even when I put myself in a direct visual line from the secondary monitor, thereby confirming that the difference I’m perceiving isn’t due to the secondary monitor sitting at a slight angle from my normal computing position.
I know consumer grade LCDs are considered sub-optimal by many photo/graphics professionals, particularly those where a print is the final output, but there’s the rub. We used to do all of our photo editing on a (Spyder) color calibrated CRT, but now our office contains three LCDs and no CRTs. We do still have a CRT in our posession, but LCDs are pervasive now and many people (portraiture clients, some stock photo clients, and a large segment of our website’s audience) who view our photos will have an LCD.
I’ve been doing a little reading and am getting mixed messages. UltraMon behaves as though I can assign independent (based on Spyder color calibration) color profiles for each monitor on a single system/video card. However, a Photo.net posting states:
If you have a single card for dual monitors, you usually can calibrate only one or the other, since there is a single driver for both.
The difference between the two monitors is noticable to the naked eye, though not obvious until a single image is allowed to span both monitors, allowing a direct comparison.
I still need to try this advice from Colorvision, however: …calibrate across monitors using the same target. I also probably need to do another (“precision” mode) calibration run on both monitors, after calibrating each based on its own native whitepoint.
Of course, the above paragraph is a moot point if the Photo.net posting is accurate — in that case,the best I could do is calibrate the primary 17″ LCD on my computer with the 20″ LCD on Justin’s computer.
Color calibration. I hate it. I really, really, really hate it. And the most frustrating thing? As professional photographers, that’s only half the problem — outputting to a printer or photolab involves a whole different set of hoops to jump through!
If I have any “Eureka!” moments, I’ll post a follow-up. This all reminds me why we need to keep at least one CRT around… only problem is, neither of us wants one on our desks anymore! 
More reading: http://www.google.com/search?q=color+calibrate+dual+monitor+LCD
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