Lumenlab > Hey Question About Fresnels

Full Version: Hey Question About Fresnels

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joshin2472003

Dec 13 2006, 10:14 PM

i'm using an beseler 18" lens and a 15.4" lcd. should i use a 550 front or a 650 front fresnel. I believe the focal legnth for the lens is 547 so shouldn't 550 be the best?

jonjandran

Dec 13 2006, 11:45 PM

QUOTE (joshin2472003 @ Dec 13 2006, 06:14 PM)

i'm using an beseler 18" lens and a 15.4" lcd. should i use a 550 front or a 650 front fresnel. I believe the focal legnth for the lens is 547 so shouldn't 550 be the best?

Either would work fine. The 650mm is actually around 610mm, just so you know

And the 18" Besler has a fl of 457mm if i remember correctly

tameone

Dec 14 2006, 12:16 AM

Both work well, but you can more easily make a decision based on your throw. For shorter throws, the triplet will be further away from the LCD & fresnel so a longer FL will help. For longer throws, the triplet will be closer to the LCD & fresnel so a shorter FL would be better.

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