Film-Tech Forum ARCHIVE: white point for dcinema.

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Posted by Pepo Razzari (Member # 6961) on 06-04-2012, 11:44 AM:

Hi people.
We make dcps from time to time and test them at a showcase cinema. I would like to ask about two different problems in case anyone could help.
I go from whatever source to xyz colorspace at 5900k and dcps look a bit on the warm side on screen. I have asked the thech supervisor at the cinema and he tells me the lamp (osram 4000 or 6000) is what determines the color temperature. I understand d65 is the widely used calibration but dont know how to check this on the projector and there is certainly a difference in color between 5600 and 6500 k. It is a Christie but dont know model/make.
The other problem is that our dcps look in sync on a computer display but out by a frame on cinema. I have read somewhere the delay compensation in the audio chain differs from 3d to monoscopic. They are projecting 3d exclusively and my dcps are monoscopic. I told this to the supervisor but he tells me he does not have a way of changeing this. They use sony servers.
Any instructions you could provide on how to figure out this information and possibly change settings?
Thanks a lot in advance.
Pepo

Posted by Robert Minichino (Member # 3495) on 06-04-2012, 12:26 PM:

The color data in the DCP file is in the CIE XYZ color space (scaled and gamma encoded). The reference white is at point [3794 3960 3890], which corresponds to the chromaticity coordinates x=.3140, y=.3510. The DCinema projector is calibrated by using a test pattern at [3794 3960 3890], and (essentially) setting gains on the imagers so that the resulting light on screen is [.3140, .3510]. The lamp's color temperature is corrected by this process.

The actual white point setting happens during the RGB->XYZ conversion, which is on your side--if you set RGB white to D65, then it'll be D65 in the cinema.

If you're doing the colorspace conversion correctly, it's possible that the cinema's calibration is seriously bad.

Posted by Yinghong Wu (Member # 6908) on 06-04-2012, 09:12 PM:

We also make the dcps use with OpenDcp,And the color is good,Never met the thing which you met,Our server is Dolby DSS100 and projector is Christie cp 2000zx. [Wink]