Film-Tech Forum ARCHIVE: Lumens of lignt need for home theater

This is topic Lumens of lignt need for home theater in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Jack Culpepper (Member # 724) on 08-06-2001, 10:58 AM:

Information concerning this would be appreciated. How many lumens of light would be needed from a digital projector with a dvd source to give an acceptable screen image of 5.5ft. x 12ft with a 25 to 30 ft. throw. Also, what type of other projector requirements, if any, would be needed to give an acceptable image. Any and all/other info would be appreciated.

Posted by Perry Sun (Member # 370) on 08-06-2001, 12:00 PM:

Jack,

You're much more likely to get the answer you need by going to the AVS Forum at www.avsforum.com which has very lively discussions on home theatre projection issues.

Perry

Posted by John Pytlak (Member # 331) on 08-06-2001, 12:21 PM:

If you have a matte white screen with a gain of 1.0, the number of lumens needed to light a 5.5 x 12 foot screen to 16 footlamberts is theoretically:

(16 x 5.5 x 12) / 1.0 = 1056 lumens.

However, this assumes the rated lumen output of your projector was for the 2.18:1 aspect ratio of your screen, and included factors such as light loss in the optics. The rated output is measured under optimal conditions, and may not take lamp aging, misalignment, etc. into account. Note that the "throw" distance has nothing to do with the light required, unless it requires a less efficient lens.

A gain screen would reduce the total light required, but would be more directional and should be properly curved for proper light distribution to the audience.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion