picture brightness -- mathmaticians only pls. :) - AVS Forum
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post #1 of 5 Old 06-20-2001, 01:20 PM - Thread Starter
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i am currently using a 1000 lumen projector from 16 feet away on an 80" x 45" StudioTek 130 (1.3 gain)screen.

i was thinking of switching to a grayhawk (.9 gain?) screen that is 96" x 54".

i calculate that the average screen brightness goes from 52 ft lamberts to 25. Is this right?....and does it matter?
(I have full light control). is it worth the tradeoff...i mean both figures seem excessively high relative to a cinema, i think.

thanks,
Rob
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post #2 of 5 Old 06-21-2001, 05:40 PM
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For the Thick Headed please repeat brightness calculation 101 Formula:


Where does the throw distance come into the equation?


80 x 45 is 3600 sq inches or 300 sq feet. Now what?

Can some one please post this formula?

I found it:
http://www.avsforum.com/ubb/Forum9/HTML/000460.html


[This message has been edited by CINERAMAX (edited 06-21-2001).]
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post #3 of 5 Old 06-21-2001, 09:14 PM
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Rob,

Congratulations, you have just passed screen math 101!

Since you have full light control there is no doubt you do not need 52 footlamberts. 25 is more than enough and since I am assuming you are using a digital projector, remember that black level will be proportionately better in your proposed setup. Contrast will also be twice what you had before unless you were running the projector at "full open".
Note that digital projectors seldom are up to spec when adjusted for proper greyscale, usually you get some 20-30 % less in practice.
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post #4 of 5 Old 06-22-2001, 08:54 AM
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Quote:
80 x 45 is 3600 sq inches or 300 sq feet
You probably figured this out already, but there are 144 sq inches in a sq foot, not 12. So th 80 x 45 screen is 25 sq feet.

Matt
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post #5 of 5 Old 06-23-2001, 04:04 PM
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Todd: I did not figure it out, thanks for the heads up. I was using a POCKET HANDYMAN conversion calculatior, which ovbiated the square part. Thus converting inches to feet lianearly, thanks...
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