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I have been told that using a Mircoperfed screen with a DLP projector can cause rainbows and other problems to occur when the pixels line-up with the holes. Is this true and if so, is there a solution to the problem?
 

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Yes I have seen this happen with a DiLA projector. In this case there were several different problems. In the first problem vertical bands of slightly varied gray appeared easily seen with a blank white screen. At first I thought this was a problem with the "8 Bar" setup on the projector. Those that are familiar with DiLA calibrations will know this adjustment. On closer inspection the problem was actually an interference pattern between the projector pixel structure and the MicroPerf pattern. To find out more about the problem I used the zoom and focus controls on the projector to change the size of the pixel structure in relation to the MicroPerf pattern. As I would change the size of the image on the screen I would see the vertical bands come and go as well as a definite screen door pattern come and go. Moving the projector and changing the zoom setting had no effect on the patterns as this will only change the throw distance but the correct image size and focus would actually remain the same. If you took the projector slightly out of focus the patterns would be reduced but at the expense of sharp focus. In the final analysis there were only two acceptable cures. One was to increase the image size until the patterns disappeared and lose the overscaned part of the image. The second was to decrease the size of the image until the patterns disapeared and repaint the black borders on the edges of the screen to accommodate the smaller image size. It this particular case we did the latter. Stewart provided the dealer with the name of the proper black paint to use. The screen was 9'x12' and we lost about 8"s of width. In addition the extra wide black area was useful in hiding the halo effect at the edges of the projected image.


This was with a DiLA projector which has a very fine pixel structure and I am sure at a particular but different image size the same problem could appear with both DLP and most LCD projectors.
 
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