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Problem videotaping DLP screen

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Dave_S
Problem videotaping DLP screen
on Nov 7, 2005 at 4:34:05 pm

I got a big surprise the other day when I was taping some footage for a program in a room where video projection was happening. Haven't had many problems in this regard lately, other than the usual balancing of light levels. This day, I experienced a wild flicker on my viewfinder, coming from the powerpoint projection. Even without including the projector screen in the video frame, just the light emanating from the screen and falling on the scene I was shooting was enough to cause the scene to flicker objectionably. No setting on the variable shutter speed would alleviate the problem.

I later found out that the client had just upgraded their projectors from LCD to DLP models. I assume that the color wheel of the DLP projector caused this artifact.

Has anyone else experienced this? Anybody know for sure what was happening here? Anybody figured out a solution?

Thanks!


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tony salgado
Re: Problem videotaping DLP screen
on Nov 8, 2005 at 4:50:41 pm



Dave,


Depending on what camera you where using (IT chip versus FIT) you may have not had the range of shutter rates to deal with the DLP refresh rate.
The frame rate your camera was set to also affects the shutter range.

FYI- IT CCD's shutter rates can go lower than FIT CCD's.

However there are some refresh rates that are in between the camera shutter rates which make it impossible to completely dial out any flicker.

What shutter rate did you find came close to dealing with the flicker?

What frame rate where you shooting at?

Another solution is to have the video projectionist change the refresh rate to you 60HZ if you are shooting 60i.



Tony Salgado


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