Film-Tech Forum ARCHIVE: Ability Of Consumer Digital Projectors

This is topic Ability Of Consumer Digital Projectors in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Robert E. Allen (Member # 1351) on 04-16-2010, 12:29 AM:

I'm planning a mini cinema. I will admit I'm a film guy and know nothing about digital equipment (other than those I've run for pre-show). I will have a 40' throw to an 8' x 20' screen. Can consumer type digital projectors handle this and how many lumens do I want. Also can those machines do both 'scope and flat with a lens change? Thanks for your help.

Posted by Scott Norwood (Member # 30) on 04-16-2010, 08:27 AM:

Your screen sizes will be as follows:

8' x 10.6' (4x3)
8' x 11' (1.37)
8' x 13.3' (1.66)
8' x 14.2' (16x9)
8' x 14.8' (1.85)
8' x 18.8' (scope)

You will want masking stops for each format. Since video is not entirely standardized, you will also want the ability to bump the masking one way or the other, in case you are showing something that is slightly wider or narrower than a standard format.

One issue that you will run into will be letterboxed versions of subtitled material, where the subtitles extend into the letterbox area. This is annoying, and it happens all the time.

For a video projector with a 16x9 chip, you will need a zoom lens that will cover a throw ratio (throw/width) of 2.12-2.82. This should be do-able with one lens. This will let you zoom between 16x9 and 2.35, while filling the screen. Narrower ratios can be pillarboxed (black borders on the sides) within the 16x9 image.

The area of the largest image will be 10.6' x 18.8' (including unused area above and below the screen), which is about 200 square feet. The cinema standard of 16fL represents 16 lumens per square foot on a 1.0 gain screen (the video standard is actually 12fL, but a slightly brighter image may not be a bad thing). You would therefore need at least 3200 lumens. Since most brightness ratings for video projectors are somewhat optimistic, you really want a 4500-5000 lumen unit or a higher gain screen.

All of this applies regardless of the make and model of the unit that you choose. Unless it has a 4x3 chip, which is becoming less common.

I know that you are aware of the licensing issues involved here, but I will point this out anyway, for the sake of others who may stumble on this thread: copyrighted material must be licensed in order to be legally screened, regardless of whether admission is charged.