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Topic: Dark Picture
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Aaron Sisemore
Flaming Ribs beat Reeses Peanut Butter Cups any day!
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Posts: 3061
From: Rockwall TX USA
Registered: Sep 1999
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posted 05-04-2001 12:03 AM
If the bulbs are new, a dark image could be caused by one of the following:-Bulb of too low of a wattage for the screen size and throw. -Dirty, damaged and/or misaligned reflector(s) or other lamphouse internal optics -Projector misaligned to lamphouse -Misaligned bulb focus -Dirty optical path (lens/portglass/screen) -Lamphouse power problems (bad diode(s), etc) -Fire shutters or electric dowsers sticking partially closed Aaron
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John Pytlak
Film God
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Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000
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posted 05-04-2001 06:43 AM
Standard SMPTE 196M specifies an aim of 16 footlamberts, with an allowed range of 12 to 22 footlamberts. If your lamphouses were originally bright enough, I suspect either misalignment/misfocusing of the optics, or deterioration of the optical components (especially the reflector).As a "rule of thumb", a gain=1 matte white flat screen requires approximately 5 watts per square foot to light properly with a properly aligned lamphouse and normal (2 blade) shutter and optics. With a gain=1.5 curved screen, figure about 4 watts per square foot. Here are some articles on the subject: http://www.kodak.com/US/en/motion/newsletters/reel/spring98/pointers.shtml http://www.kodak.com/US/en/motion/newsletters/notes/june2000/pytlak.shtml http://www.kodak.com/US/en/motion/newsletters/notes/march2000/pytlak.shtml http://www.kodak.com/US/en/motion/newsletters/reel/december99/pytlak.shtml http://www.kodak.com/US/en/motion/newsletters/reel/december99/harknessHall.shtml ------------------ 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
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