Calculate Black Crush

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  • #141394

    Ben
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    I just tryed to make 1% visible with gamma 2.4 on a 1000 contrast screen.   I had black level set and could see 2%.   I lower black level below its default till i could not see 2% and raised it till could.   I used hcfr and found a 2.4 bt1886 black input offset that matched 1% to the 2% reading.   We could use display cal with that offset changed to output offset.  5% is 95%.    Mine input was 15% in front of screen and 25% sitting away 10 feet at a slight angle.   Would you use the offset method or just overide the low 5% and use 0% input offset?

    How do we set display cal to bt 1886 2.4 gamma and 75% output offset?     2.4 relative 75% ?      I noticed 2.4 relative 100 output offset was the same as auto black point correction per my display.   But autoblack had lost 300 contrast.   It adjusted the 0,0,0 RGB .     I used coolerchecker display plus.

    #141414

    Ben
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    Getting the gamma of something just visual and getting gamma at your desired gamma with a low end tail going down to that is a good approach too.   0 output offset is the closest to this.   Btt1886 with a gamma  is good for this.

    #141422

    Ben
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    I found it is a bug.   I manually adjusted lut 1 of 255 using Calibrilla .     It did not effect measureing RGB 1 of 255 in HCFR black levels.   I changed 2 and it changed HCFR measure of 1 .  I made 2 equal to 3 in Calibrilla and it gave close enough RGB numbers in HCFR 1,1,7 in HCFR instead of 0,0,7  at 2.4 gamma.   At 2.2 gamma  tv OSD it higher than it needs to be by 1 RGB values .   It is 1 RGB less it needs to be without the lut changed.   At 7 percent rgb is 4 high but 5% is right. and 4 is less.  It looks fine especially sitting back.

    I wonder if 0 to 255 lut is 0 to 255 RGB and each lut is supposed to change a RGB value in limited or full mode.   And I wonder why.    Anyone know?

    Wish we could just use 0 to 5% displaycal calibration.   Fine tuneing lut by hand is fun but not fun checking for errors and remeasuring 10 times like displaycal.  I do not think displaycal catches the lut 1 failure and corrects it.

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