Film-Tech Forum ARCHIVE: What is the Recommanded christie bulb light intensity

This is topic What is the Recommanded christie bulb light intensity in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Alexander Tarakin (Member # 7140) on 06-05-2018, 11:27 AM:

Dear all,

Can someone please advice on what is the recommanded light intensity for Christie bulbs in a christie projector CP2220, CP2230, CP4230.

CDXL3,000
CDXL4,500
CDXL6,000

Thank you.

Posted by Dave Macaulay (Member # 813) on 06-06-2018, 01:05 AM:

Not sure what you're asking.
I think the number you get for "lamp brightness" in lamp alignment is undefined. Since this number is only used as a data point for light-loc there's no reason for Christie to calibrate it to a measured light level value in the light engine. As far as I know, they do not.
I don't know the typical value one might get from a given lamp. I've seen a fairly wide range but I've never noted the readings.
If you mean screen brightness values, these have no consistency unless the screen size and gain - plus projection geometry with a gain screen - are identical.

Posted by Alexander Tarakin (Member # 7140) on 06-09-2018, 01:52 PM:

Hello Dave,

Let me explain please...
I have two christie projectors CP4230 with a CDXL-6000 bulbs.
The projection geometry and screen size are almost identical.
One projector is with an intensity of 54,000 and the other with 30,000.
The one with the 54K intensity projects a much sharper, clearer and more colorful image.
The one with the 30K is projecting a darker and less sharper and clearer image.

So, is there a chance that a reflector / UV filter / integrator rod or any other optics related parts should be replaced? or maybe the image quality difference is due to some other reason?

thank you.

Posted by Dave Macaulay (Member # 813) on 06-09-2018, 03:40 PM:

It may be that the prism is dirty. I haven't had problems with a Christie integrator. And "almost identical" means what? A modest change in screen HxW can mean quite a change in area.
Is one older than the other? Is one closer to a doorway where popcorn smoke wafts up from the lobby? I see a big difference in filter loading when popcorn smell gets to a booth, with the systems closest to the source markedly worse. Christies can get their light engine optics coated with this stuff, the LAD filter is pretty good but some gets through.
Inspect the collectors and folding mirrors, these get unfiltered air and soil faster than the prism.
Dirty prism and DMD surfaces drop brightness, contrast, and color saturation