Measured Gamma

[pyron]

I have some questions regarding the measured gamma in the verification graph.

Should it be flat across the graph or having some deviation on x: 5 or x:10 is fine?

I mean I’m calibrating to Rec.1886 2.4 gamma (absolute), and the low end is a bit bright. Is there a way to improve gamma calibration? Maybe a longer patch sequence?

Using i1Display Pro Plus and Dell U2715H

• This topic was modified 3 years, 10 months ago by pyron.

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[Vincent]

Do not use Rec1886, it not meant for that kind of low contrast displays (less that 3000:1 or maybe higher). Use 2.4 instead, otherwise Rec1886 will work as intened by specificiation (google ITU Rec1886) and result in a lower gamma than 2.4

Also near black it will go to lower gamma values, no matter what you do, because of limited display contrast and keeping a minimum of brightness separation between greys. Your display cannot go darker there.

• This reply was modified 3 years, 10 months ago by Vincent.

[pyron]

Thanks for the reply. I though it had to do more with the black level rather than contrast ratio. Something around 0.03 cd/m2 in order to use absolute. Also the contrast ratio diminishes when you set the white level to 100 nits.

I will try to calibrate to 2.4 relative tonight and longer patches and see how it goes.

[Vincent]

Yes, black level. But black level with typical grading setup is about 0.10 on a typical IPS. With other technologies with higer contrast black level is low at the same white level. Since typical white level is fixed fo these tasks, let’s say 100cd/m2 @D65 … it is actually a matter of contrast, not to black level. Static contrast ratio is a “window”, you fix white level => you get a black level, not the opposite.

• This reply was modified 3 years, 9 months ago by Vincent.
• This reply was modified 3 years, 9 months ago by Vincent.

[pyron]

Actually the gamma image was from the HDTV, here is the before/after of my PC display. As you can see increasing the patches to ~822 yields worse results. At 15 black gamma still doesn’t reach 2.4 on the new calibration.

Is there any tip to improve gamma? Would a Rec.1886 compliant display show a better measurements?

These are my settings:

• This reply was modified 3 years, 9 months ago by pyron.

[Vincent]

On limited contrast displays gamma has to bend and go lower. Otherwise you’ll clip and you do not want it. This is the best you can get on a 1000:1 IPS.

• This reply was modified 3 years, 9 months ago by Vincent.

[pyron]

I understand, thanks for the help!

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