I joined AVS Forums a while back and while they were generally helpful, they weren't as helpful as you have regarding this very issue.TSM wrote:You have to remember that a 6 bit color palette only has 64 steps. When you attempt to modify your gamma curve, you are running into a granularity problem at the lower end of the scale. For example (making up numbers) normally working with 8 bit color your 20% target may be 5,7,3 and 30% may be 12,17,9. With 6 bit color your 20% target may be 2,3,2 and 30% may be 6,7,5. Trying to hit D65 exactly at the low end is going to be literally impossible. Then you add in the dithering. Dithering doesn't magically give you more dynamic range. What it attempts to do it so add more granularity through averaging. You may get a 2,2,1 / 3,4,4 checkerboard pattern instead of 2,3,2 and so on. Then when you take this logically a step further, you realize that a solid checkerboard field is the best case scenario. When you look at ramps for instance, the monitor does it's best to dither adjacent pixels of slightly differing luminances together as best it can. This is most likely the culprit for the tinting you are seeing. When you are attempting to micromanage the lower end with a LUT, you are for instance making 20% white slightly blue, 25% slightly red, 30% slightly green, etc. When the monitor is then mixing all these together with dithering, you are probably getting a tint from the interaction.
There are only 64 steps per color at most, and that the act of trying to change the white point lowers this even further for at least 2 of the primaries. At best you will get an approximation of what you want. This is where your professional skills will come into play. You will have to determine what the most acceptable compromise is. The meter does it's best to approximate human vision, but in the end you have to determine what looks most natural to the human eye.
Take what I say with a huge grain of salt as I'm not a professional calibrator. I highly recommend heading over to the avs forum display calibration area. It's one of the greatest resources online for calibrators:
http://www.avsforum.com/f/139/display-calibration
As for your questions about using ULMB, you would probably be best to direct them at either the forum I linked to or the company that you purchased your probe and software from. The strobing back light may cause the probe's results to be inaccurate. If so, this may be addressed by calibration software that takes this behavior into account.
I understand what you are saying, but the levels that have whichever tint continue having that exact tint without any change at all. I can see interaction, but that is not what is causing the effect... There are areas that are practically impossible to calibrate, regardless of the white balance setting used. I had it even worse with my original VG248QE, so I had it replaced with this one, which was somewhat better, but still sucked like I explained. I am not seeing the checkerboard pattern anywhere, btw... something I saw other people talk about, but I just do not see it...
In this test - http://www.lagom.nl/lcd-test/gradient.php the dark 0-10% or so is like a giant purple band, then 10-20% or so looks very neutral, and then 20-100% are fine with only LUT interpolation banding, which I could care less for. Its the 0-10% that destroys my gaming experience as no amount of WB manipulation, which is quite impossible to do anyway, makes the purple turn neutral. I think its not just not capable of doing it... And that is with 350:1 contrast ratio...
The non-LightBoost mode is better, but still has that un-calibrate-able purple band 0-10%, even after calibration.
This is just very interesting to me from a professional point of view - I never ran across a display device other than my own monitor, that would behave like this. Not being capable of producing gray is just... out of whack!
I did see others complain of the same tint, but now it seems nobody except for me gets that purple band 0-10% of the grayscale ramp. I was hoping G-Sync would fix it, but now it doesn't look like it will. At least now I know to save the money instead of expecting G-Sync to normalize 0-10% somehow.