Two NEC monitors suddenly don't match

[PeterAit]

I have the PA301W and the 2690WUXi and use Spectraview for calibration. For 2+ years they have worked perfectly and matched each other exactly in image brightness, color, and contrast. Suddenly they don't quite match - the 2690 is slightly, but noticeably, warmer than the other even right after a calibration. I believe I do the calibration properly - shield from stray light, allow to warm up, etc. What could be the cause of this? Running Windows 7.

[digitaldog]

Don't know the cause but the fix is to change the calibration targets to reduce the warmth (higher white point for backlight) until they match.

[howardm]

My guess would be that the CCFL backlight has reached a point in age/hours where it's color is starting to shift a bit or maybe phosphor burnout.

[PeterAit]

My guess would be that the CCFL backlight has reached a point in age/hours where it's color is starting to shift a bit or maybe phosphor burnout.

But isn't the calibration process intended to correct for these age changes?

[howardm]

If that was true, then taking 2 different & random panels and calibrating to the same targets would yield the same visual results but that doesn't
happen in the real world