CurtPalme.com Home Theater Forum

[rds]

Hi all,
I need your help with the correct use of a few controls in my barco gr 808s

How set the red green and blue gains and cutoff (please explain wich part of the color spectrum affect) how realy work?
and the red and blue midlight too, how set properly.
The gains are for the high color and the cuts for the low?
I use a Sony monitor to equal the color balance by eye, not have any device to messure.
Thanks and happy new year for all!
Rubén

[r.bauer]

Please do not adjust Blue and Red midlights if you do not have a color analyser! Set them to factory defaults settings and don't touch them They can seriously screw up color balance. These controls should not be adjusted at all whithout a color analyser.

Start out using the 6500k color balance. The picture will be very watchable.
You can adjust some bias/gain if required. But again, the human eye is a very poor measuring instrument.
How do you know if your sony monitor is properly calibrated? It probably is not, so that does not make much sense.

Proper calibration is a serious job for which you need serious measuring equipment. It cannot be done by eye.

[rds]

Hi Bauer,
Ok with the midligth, the sony is used in silicon graphics to run stacks of barco so they are really good calibrated.
How work the gains and cuts?
Thanks!
Rubén

[r.bauer]

OK, If you have a proper calibrated monitor at hand, then you have a good starting point.

Although the human eye is not good in observing absolute colortemperature, it is however very good in observing relative color temperature. This means that a proper calibrated monitor near or under the projection screen is a very good way to calibrate your projector's color temperature.
Put up a grayscale on both the monitor and the projector.
Set the Barco in factory defaults in the midlight menu (under service menu) press enter to enable these factory settings.

Now go into the picture tuning menu, and while you are there, set peaking to off. This is a must for every Barco owner.
In the picture tuning menu, go to color balance an select 6500k and press enter, now your projector is in default settings.
Set brightness and contrast at the appropriate levels using an appropriate testpattern on the projector and on the monitor. If you need to adjust G2, now your projector is perfectly set to adjust G2 in the service menu.

Put up a stepped grayscale on both the monitor and the projector.
Now you can adjust Cut off and Gain in the picture tuning menu. Cut off is for the 'dark areas' of the grayscale and Gain is for the bright areas of the picture.

Look at the grayscale on the monitor and compare it to the grayscale on the screen. Adjust where appropriate, but take slow steps. Cut off and Gain do interact, so adjusting is an iterative process. Observe that your eye is able to see the difference in colortemperature when changing any Cut off or Gain setting (of any color) by just 1 step up or down. This shows you how acurate you are able to see a difference in color.

Disclaimer:
- You will not be able to verify that your entire display chain (from source to screen) has the proper Gamma setting. that can only be measured with a proper analyser. Proper Gamma is very important for that last ounce of blacklevel performance and 3D depth in movies.
- You will not be able to tell when one of the three CRT's has reached it's maximum lightoutput. For instance red and green might have more lightoutput than blue. In this case your greyscale might be 'about right' until say 80 IRE, beyond 80 IRE blue will drop and you will not be able to obtain a proper grayscale all the way from 10 to 100 IRE. Lowering the contrast might help, but you still will not be able to determine at what contrast setting one (the blue) CRT has reached its maximum lightoutput.

[rds]

Wow,
Great, do you say black level is cutoff or brigthness?
Thanks!
Rubén

[r.bauer]

I have edited my post and used the proper 'Barco' terms.

[rds]

Hi Bauer,
Your detailed descriptions are follow in a few minutes.
Thanks for your time and experience!
Regards
Rubén