I calibrated the screen first without unchecking the "auto change for ambient light" thing, and i could see in the response graph of the profiler jumps and dips that weren't there when the option was unchecked. This makes me think that the profiling puck detects differences in colour depending on the brightness of the backlighting, and so to keep accurate, you want to keep the back lighting at the same level as when you did the profiling.
I agree that the brightness keys will only change the intensity of the screen's back light, but i would say that this level has an effect in the screen's colour accuracy: some colours will be shifted more than others, and so if you're after colour accuracy you should view with the same level of back light (and ambient light too, while we're at it!).
For example, if you have three different dark colours, and you dim them all down, they might all go to black, and hence look the same. If you want to distinguish them, you need to keep the back light up. The same goes for light colours, but in the other direction - you'll need to keep the back light down. And so if you want to keep differences in both dark and light colours, you'll need to keep the back light in the same place. After spouting that off, i hope i'm right
tho someone with BasICColor (which can verify a profile) and 5 mins to spare, should be able to settle the argument.
Cheers
