Originally Posted by Elix
Furthermore, there are 4 gamma ramps: W, R, G, B. W stands for 'white' and by design altering it shouldn't mess with color balance... but it does.
Otherwise I'm very happy with this projector.
As you probably know, with most projectors, you have to keep going back and forth anyways between Grayscale patterns, Gamma Settings, and Gamut patterns (more so on grayscale - gamut), so I don't see this as anything more than a minor inconvenience to be honest.
Yes it is more tedious, but that's often what we are forced into anyways when calibrating many of these projectors. Just be glad it has individual gamma point adjustments at all, heck some projectors don't even have that and you do it purely by gray-scale controls and one master GAMMA whitepoint (which is a pain). In this latter case, you end up going back and forth a lot, but it still works (well within the boundary limits of the gamma error anyhow).
From my understanding of this issue, it is common on many projectors. The W or white point gamma is really nothing more than combing all three at once - RGB, because after all white is all the colors combined on the spectrum.
The problem is our gray-scale is usually not perfect across the entire IRE range (or rarely at this point in the calibration). With an imperfect gray-scale, the white-point adjustment becomes non-linear in some cases (hence like adjusting each RGB as a percentage individually instead of bumping them up equally individually). Another way of thinking about it is, you are sort of moving the error that existed at 10 IRE to 20 IRE (or vice versa) as you adjust the gamma by using the global whitepoint (just for explanation purposes), so unless your gray-scale is perfect across the entire IRE range, then moving whitepoint isn't totally abnormal to also cause it to mess up gray-scale readings. I know some projectors don't do it as much, but I bet it's because they are using some firmware code to compensate the error as the whitepoint is adjusted (hard to explain).
You just rinse and repeat all the different steps until you get as close as you can, that's how it almost always ends up. Only a couple projectors, like the Sony's or Benq w1070 are so freaking close or simple to calibrate that we don't even have to go back and forth very often.