# Light Output Question For Front Projector

Discussion in 'Displays' started by James Edward, Aug 8, 2003.

1. ### James Edward Supporting Actor

Joined:
May 1, 2000
Messages:
855
0
A friend will be renting a FP for a party he is having. His intention is to project concert DVD's on an 8ft x 8ft screen outdoors.
He lives in upstate NY, so ambient light from homes, streetlights, etc., will not interfere. His choices are: 2000 lumen projector for \$200 or a 3000 lumen projector for \$300.
Should 2000 lumens( Panny TL-520) be sufficient, or should he spring for the brighter unit? Would a full moon make a difference as far as needed light output?
I'm not familiar with projectors, so any advice is appreciated. Thanks

2. ### Gabriel_Lam Screenwriter

Joined:
Mar 7, 2002
Messages:
1,402
0
That's a BIG screen.

Let's start with just a tiny bit of theory. The projected image would be 6' x 8' (or 72" x 96"). This gives you a 120" diagonal screen. There are a total of 48 square feet on that screen.

We'll assume, for now that the screen has a 1.0 gain (the light shined at it is reflected with exactly the same intensity).

With a 2000 ANSI lumen projector, you'll probably need to account for at least 20% loss of brightness due to calibration. That's reasonably low, most projectors are higher than this. We're down to 1600 ANSI lumens.

Projectors will only do full brightness with a brand new bulb. As UHP, SHP, NSH, and P-VIP bulbs age, they drop pretty quickly down about 20-25% brightness, and stay about there until their death. Xenon bulbs fall rapidly to 20%, and then slowly down to 50% at their end of life. The Panny is not Xenon, and I'm guessing the other one isn't either. We're down to about 1280 lumens.

With a 48 sq foot screen, we're at about 26.7 ft-lamberts of illumination, which is not bad at all (THX recommends 16 +/- 2 ft-lamberts). This being said, if the moon is really bright, the picture may still wash out.

The way our eyes see "brightness" is not linear. A 3000 lumen projector will not seem 50% brighter than a 2000 lumen. At best, it'll seem about 10-15% brighter.

What kind of screen does he plan to use?

Joined:
May 1, 2000
Messages:
855