Film-Tech Forum ARCHIVE: Weird "screen door" effect on christie

This is topic Weird "screen door" effect on christie in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Kyle Butler (Member # 5601) on 09-11-2010, 04:14 PM:

I went over to a local AMC a week ago to catch Machete, and i noticed something weird with their projector.
They converted to all digital about 3 years ago.
I noticed a weird "screen door" like effect on the screen.
It wasn't pixelation though.
It was bigger, and all of the boxes seemed to have a redish/blue glow. Its hard to explain. Seems like some form of image degradation.

anybody have any ideas?

Posted by Marco Giustini (Member # 4544) on 09-11-2010, 04:33 PM:

Moiré?

Posted by Chase Taylor (Member # 778) on 09-11-2010, 04:35 PM:

It could have been bad convergence or if it was on the edge of the image it could be the integrator rod at fault.

Posted by Kyle Butler (Member # 5601) on 09-11-2010, 05:34 PM:

The look of Moire best describes it, but i don't think it was moire.
the pattern was too uniform, static, and highly visible irregardless of the picture shown.

I guess it could have been the convergence.
It wasn't anywhere near the edges of the screen, mostly the center of the right side.

Posted by David E. Nedrow (Member # 4981) on 09-12-2010, 12:30 PM:

quote: Kyle Butler
The look of Moire best describes it, but i don't think it was moire.
the pattern was too uniform, static, and highly visible irregardless of the picture shown.

Still sounds like moire caused by the pixel elements of the projector being too closely aligned to the perforations in the screen. That type of moire pattern won't vary in shape/size, since the screen and projection element aren't changing in relation to one another.

Some screens can now be ordered with a "digital projection" option, which basically cuts the screen in such a way that the perforations aren't perfectly level, thereby making it less likely for screen/projector moire to be apparent.

We have to slightly defocus our digital projector to reduce the moire pattern.

But remember, digital cinema will always be perfect when compared to film cinema. Just ignore any projection/screen/sound/seating problems. [Wink]

-David

Posted by Kyle Butler (Member # 5601) on 09-12-2010, 10:22 PM:

Ive heard of that being a problem, but i went to this theater the first day they re-opened with all digital,and it certainly looked nothing like this.

It actually looked decent for d-crapema (copyright 2010 tony bandera)

Posted by Carsten Kurz (Member # 5396) on 09-14-2010, 06:18 AM:

What was the screen size and how far from the screen were you sitting?
How do you know it's a Christie?

At least if you're close enough to the screen, issues are relatively easy to analyze usually. Good optics properly focused will reproduce sharp edges of any pixel artifacts. Anything 'blurry' will usually be related to lens issues. Panel deconvergence will usually also be seen uniformly accross the screen. Anything like convergence NOT uniformly spread accross the screen will again have to do something to do with the lens. Of course, the more issues present at the same time, the less chance to tell which individual issues these go back to.

- Carsten