Ah excellent. We're getting into screen shots.
I wrote the following in another thread a couple of months ago:
This is a really good topic for all of us taking screen shots.
I've been getting more and more into photography after starting to take portrait photos of my family rather than send them to a professional. I've only obtained enough information to become dangerous
From what I've read in photo instruction books, online, and in some brief medical papers is that there is 'White Balancing Interpretation' that our minds conduct between our eyes receptors and the brains final analysis. So in essence, when a subject is fully lit by fluorescent, tungston, hallogen, candescent or sunlight they all appear relatively 'White' to us. A camera captures the light in it's basic form, i.e. fluorescent = bluish, tungston = warm or orangish, sunlight = pure during mid-day, etc. The cameras output must then be adjusted to how our brain interprets it to make it appear correctly to how we see it. Make sense?
Cameras, even the top SLR's, are only okay at White Balance. On the upper-end cameras there is a blanking white balance method that works the best but still is not perfect. You essentially take 3 consecutive photos at 3 different settings. The camera then adjusts and averages for the best white balance.
The best white balance technique is to utilize a software program like Photoshop to adjust the Histogram levels so that Red, Blue, and Green are adjusted to cover the full spectrum from 0 to 255.
Photographers will use the black & white cards to white balance, but more importantly to adjust the iso, shutter, and apperture for the correct exposure. For the screen shots, making sure you have the correct exposure is more important. If you desire, you can then adjust the White Balance in Photoshop.
I came up with a method to try & compare my old LT150 projector versus the new DT500. I used my Nikon D80 in full manual. ISO, Aperture, Shutter, White Balance, Contrast, etc were all manual in normal settings. Here is the link to the thread discussing the camera settings & how the shots were taken: http://www.avsforum.com/avs-vb/showthread.php?t=840495