Calibrating VT/ZT60 in panel brightness high
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When I first checked out the VT60, I saw that using panel brightness high crushed whites unless contrast was turned so low that light output was pitifully low. It crushed everything above 97 or 98%.
In PB high, if you take 10% interval readings and adjust the 10 point controls normally, you will end up with a very large luminance peak/gamma dip at 95% that won’t show up in your measurements, and most likely the white will also be crushed.
Since then, I’ve found out how to remedy that, and these displays can get some surprisingly high light output. Using it, there is a definite improvement in punchiness, especially in typical living room lighting.
PB high, with any normal contrast setting, causes a slight displacement at the bright end of the 10 point adjustments. The 100% control actually effects 95%. Use this to tame the 95% luminance peak and instead of white crush, you’ll actually end up with a little WTW headroom.
The following is the procedure I have found to work well, using the Pro 1/2 modes:
Using CalMAN autocal:
Lay the groundwork by switching to Panel Brightness High, set gamma to 2.4, set contrast (I usually use a high but not maxed out number for psychological reasons), set brightness (will most likely end up in the high teens). Set the RGB gains by minimizing dE at 100%- do not use 80% or any thing else! ONLY worry about 100% with the gains. I would suggest not making adjustments to the RGB cuts, but if you want to, use 10% as the adjustment point and keep the adjustments mild. Then go back and re-check the brightness adjustment.
Start CalMAN’s 10 point autocal, using a dE2000 target of .4. With a fast meter, the procedure should take less than 3 minutes. Things will not be ideal at this point, but you’ll go back and rework the 10 point controls after doing the CMS.
Move on to the CMS adjustments. I suggest doing them with the saturation sweeps rather than the normal classic color gamut measurements. Run CalMAN’s autocal with the following settings: 5% saturation sweeps, 95% saturation point, 75% luminance, dE2000 target of .2. It should not take as long as the 10 point autocal. Switch to 25% ramps and take a full sweeps run. Things should be balanced well, and dE’s should be very low. You can manually tweak the CMS controls then if desired (I like to, but it shouldn’t be absolutely necessary).
Now comes the tricky part, where you will compensate for the 95% luminance peak and eliminate the white crush. CalMan will have the 100% luminance control at 0, and it will have DRAMATICALLY reduced luminance at 90% and below to get what appears to be a good gamma (they will probably be around -28 or more). However, if you measure with 5% increments, you’ll find it’s really messed up at the high end. Go ahead and switch to a levels run that uses 5% increments (or at least includes a 95% reading). Take a measurement run. Start your manual tweaking by taking the luminance from 0 down to about -10. Switch to a new tab if desired and take another measurement run. Things should be looking much better at 95%, though everything else will be a little more messed up. Remembering 100% was already adjusted by your RGB gain adjustment and the 100% controls are actually effecting 95%, manually tweak the high end until you have a good gamma and grayscale tracking, especially from 90-100%. Then expand your tweaking to include the entire range. With patience, you will be able to get smooth gamma and grayscale tracking.
Using ChromaPure with ControlCal (can also be adapted to non-autocal CalMAN with ControlCal):
Lay the groundwork by switching to Panel Brightness High, set gamma to 2.4, set contrast (I usually use a high but not maxed out number for psychological reasons), set brightness (will most likely end up in the high teens). Using ChromaPure’s White Balance module, set the RGB gains (high) by minimizing dE at 100%- do not use 80% or any thing else! ONLY worry about 100% with the gains. I would suggest not making adjustments to the RGB cuts (low), but if you want to, use 10% as the adjustment point and keep the adjustments mild. Then go back and re-check the brightness adjustment.
Make sure you are set to use 5% increment readings in ChromaPure’s Options – Calibration – Grayscale.
In ControlCal, go to the gamma 10 pt tab. Before even starting any measurements, get yourself in the ballpark by setting level 100 to around -10 and levels 40-90 to around -23. Then, using ChromaPure’s gamma module and using 5% increments, take your 100% white reference setting. Don’t attempt to make any adjustments to that; remember you set 100% with your RGB gains. move on down to 95%. Remember that the 100% w/b 10 pt and gamma 10 pt adjustments actually effect 95%, not 100%. That displacement is only an issue at the very bright end. Work your way down as you would normally do. After you’re finished, give the display a little break and then take another pass. Don’t be worried if some of your 10 pt gamma controls end up in the -35 to -40 range.
Do CMS, using 75% stim level and either Rec. 709 or 75% of Rec. 709 as your target in ChromaPure’s options – Calibration – Reference Gamut.
Then go back and touch up the 10 point controls. Double check by taking a full run in ChromaPure’s Post-Calibration GrayScale module even if you’re not sure you’re done. Be patient and go back and make corrections if there’s something you don’t like in the results. When you’ve reached the level of precision you desire, you’re done.
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