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picture brightness -- mathmaticians only pls. :)

198 Views 4 Replies 4 Participants Last post by CINERAMAX, Jun 23, 2001

Robster1958

Discussion Starter · Jun 20, 2001

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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CINERAMAX

· #2 · Jun 22, 2001

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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Iceman

· #3 · Jun 22, 2001

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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Matthew Todd

· #4 · Jun 22, 2001

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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CINERAMAX

· #5 · Jun 23, 2001

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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