Datacolor User to User Support Group.

I'm using an Apple Cinema display 23" and have used the Eye-One for calibration with pretty 
good success. I recently bought the PFP suite with the spyder and the monitor profiles also 
seem pretty good. 

However, and I don't think this is a problem with the calibration equipment, when I try to 
measure and nail down the luminance, the level will keep sliding either up or down over the 
course of many minutes, making it practically impossible to know if the luminance is correct 
even if I select it when it hits the target (does the monitor keep shifting afterward? I don't 
know!). I have noticed this on both my Eyeone and Spyder. 

And this is after long warmup times--most recently after having been on continuously for 
about eight hours. 

Is this normal? I don't think my display was always doing that. What can I do? 

Also... I figured out on my own how to choose a luminance level, but I'm wondering if I 
should have a target figure for the black measurement too

thanks

dave