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Every body talks about the projectors and the bulb but what is the best projection angle to (1) Obtain the best light on the screen.
(2) Limit the distortion/alignment of the film for best quality.

I have heard that 0 degrees is the best. But somepeople are saying that a higher angle directs more light to the audience.

What are your thoughts?

Does anybody have any experiece on projection angles over 12-15 degrees and what the pictire looked like?

How are projection boxes being designed so that the smaller cinemas can still obtain a good angle and the multiplex still have some blockbuster screens?

Dead straight on, or so the light source is perpendicular to the center of the screen plane...

To direct screen light toward the audience you would need to tilt the screen...

I was once in a down-at-the-heels little old theater in downtown LA that had probably begun life as a vaudeville spot at the turn of the century... I was surprized to see that the booth was a little box with a ladder, high up on the RH wall and 1/3 of the distance from the rear wall to the screen... I was even more surprized with the picture quality they were projecting, but it was obvious they were limiting the horizontal spread: the "wide screen" flat image looked more like 1:37 to 1.00... The horizontal focus was amazingly good, so they must have used extremely slow lenses with high focus depth...

Above 15 degrees you'll have lots of keystoning and top to bottom focus problems...

No matter how tall the screen, if the booth ports are high enough to be perpendicular to the center of the screen plane it'll work fine...

Any angle to the screen introduces keystone distortion, which may require cropping of the image, or a special lens mount to correct somewhat.

Gain screens do act somewhat like a mirror, so you need to do "ray tracing" to see where the projector's light is reflected. In most cases, gain screens need to be properly curved to optimize illumination uniformity for the audience. With a very steep angle, tilting the screen may also be necessary (if the screen is not tilted, the light from a very high projection booth is reflected to the floor!).

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John P. Pytlak, Senior Technical Specialist
Customer Technical Services
Entertainment Imaging
Research Labs, Building 69, Room 7525A
Eastman Kodak Company
Rochester, NY 14650-1922
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