CurtPalme.com Home Theater Forum

[Corleone88]

Hello,

I have a BG808 + OPPO 103 + Lumagen XD + Darbee. After calibrating (Chromapure + Display 3 pro), I am happy with the greyscale and colours but not with the gamma (picture is too dark in low light) even if the theoritical results are ok : 2.22 almost everywhere in the greyscale. I tried to adjust the gamma factor on the XD (ouput->CMS->gamma factor), but if I lower it (0.85), I have to reduce the brightness of the Barco in order to get correct black with the black bars flashing pattern.
And I am not sure this is the right thing to do.
Basically, I have no idea on how to setup up the gamma correctly. I don't really know where to start and I don't know if there are patterns that I can use to set it up correctly. My only reference is the picture on my Pioneer Kuro which I think gives a great picture in low light but it is very subjective.
Thanks for your help

[Nashou66]

Try the BT.1886 gamma in the latest Chromapure the curve gives a lower gamma for the low end and raises it for the high end.

http://www.chromapure.com/colorscience-gamma.asp

[CIR Engineering]

When you get the hang of things, you can use the internal test patterns in the Lumagen along with your software to adjust the grayscale and gamma manually. This will yield much better results.

The only test patterns you need are the Lumgen black bars contrast pattern and than the white and gray widows.

craigr

[Corleone88]

[Corleone88]

[CIR Engineering]

The bar in the very center of the screen in the middle of the stair steps is black. The steps to the left of the center bar are blacker than black getting darker in 1 IRE increments. The bars to the right in the steps are above black getting brighter by 1 IRE increments.

There are four wide bars, two on either side of the center step pattern. The dark bar is 2 IRE below black and the brighter bar is 2 IRE above black.

Most of the time on a CRT you will want to just barely be able to make out the thick blacker than black bars. They should not jump off the screen, but if you sit and stare at the pattern you should eventually be able to discern the blacker than black bars... or at least that's a good starting point.

craigr

[Corleone88]

[CIR Engineering]

[Corleone88]

I calibrated my BG 808 this week-end and I am very happy with the picture now.
I followed Craig's advices to setup the black level with the brightness (=55). Then I adjusted the gamma and got a nice 2.2 gamma curve on 11 points. I added an extra point (12-point) on the 2 IRE and increased its value by 1.5 luma to get a nice picture in low light.
I watched Alien BR yesterday to check if everything looked fine. And it did, at least to my eyes
Thanks for your help.

[Nashou66]

Sweet!!! enjoy your theater!!

Nashou

[CIR Engineering]