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Old 04-29-2008   #34
Gerben Van Duyl
Join Date: Aug 2007
Location: Sydney
Posts: 21
Default Re: Proper screen size for best quality picture

Originally Posted by TheMoose View Post
I was reading some reviews on projectors & the Lumens output were between 1000 & 1500.
How do you figure out what is the ideal screen size for lumen output?
The THX ciname target is 16 foot-Lambert (ft-L), reflected of the screen(!), which is:

foot-lambert n. An obsolescent unit of luminance equal to that of a surface emitting or reflecting one lumen per square foot, a completely reflecting surface illuminated by 1 foot-candle having a luminance of 1 foot-lambert.

So, per 1,000 lumen, you can correctly illuminate 1,000/16 = 62.5 square feet of screen surface, ASSUMING perfect luminance (reflection) of the screen. Considering a gain of say 0.97 of a typical 'neutral gain' screen, the 16 ft-L would become 15.52 ft-L, which is still twice as good as most neighbourhood cinemas.

So, if you are looking at installing a 10' screen with a 16:9 ratio and 0.97 gain, you have 56 square feet of screen surface, requiring 56 / 0.97 * 16 = 923 lumens of output from the projector.

Next question, can you trust the lumens specifications from the projector manufacturer? Bottom line, you need to measure this, using appropriate equipment. A good AV dealer / installer can do this for you.

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