Additions:
In addition, it appears that there may be additional internal compensation operating over a shorter time scale, as measuring brightness in an orderly fashion from DAC 0...1024 produces a different luminance curve than when the same values are measured in random order over the period of an hour. We have yet to determine exactly what causes this. If you interleave each orderly measurement with a period of black and color channel=max, the curve matches the one made from random order pretty well, suggesting that the issue may involve some kind of feedback control with the back-light (kind of like dynamic contrast) that behaves poorly when the max luminance stays relatively constant for a long period of time. More tests are necessary.
