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Topic: Maximum Throw

Barry Floyd
Phenomenal Film Handler

Posts: 1079
From: Lebanon, Tennessee, USA
Registered: Mar 2000

posted 08-24-2000 09:38 AM

In preparation of preliminary plans for our upcoming drive-in, we are moving to the next phase of design and are trying to determine the best use of our lot, and trying to determine the maximum suggested throw for a 4kw lamphouse.

Any "rules of thumb" or design criteria available anywhere?

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 08-24-2000 10:06 AM

What make/model of lamphouse? I am assuming this is with a new reflector as well?

There's a big difference in light output between a something along the lines of a Strong Ultra80 as opposed to something like an ORC or CFS.

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Barry Floyd
Phenomenal Film Handler

Posts: 1079
From: Lebanon, Tennessee, USA
Registered: Mar 2000

posted 08-24-2000 10:14 AM

I've got a 4kw ORC, but will more than likely replace it with a Xenex II or a Christie - both 4kw minimum.

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Pat Moore
Master Film Handler

Posts: 363

Registered: Mar 2000

posted 08-24-2000 11:30 AM

Unless you're at one extreme or another (really short or really long focal length lenses), throw doesn't count as much as screen size does to determine light and power requirements.

Assuming you've got a "normal" sized drive in screen, 4kw is usually required, but there are plenty of exceptions. Consider ambient light conditions and general air quality -- if it's naturally dusty, longer throws will cost you some light. I always found drive-ins easier to light in winter because the air was cleaner -- less stuff floating around in it.

Have to say, you should include Strong in your considerations -- very good 4kw lamphouse and optical system. And yes, I'd say that even if I didn't work for us.

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Ken Layton
Phenomenal Film Handler

Posts: 1452
From: Olympia, Wash. USA
Registered: Sep 1999

posted 08-24-2000 02:10 PM

250 feet is about as far away as you want to put the projector without losing too much light. Try for a screen size of 40 by 90 feet.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 08-24-2000 08:45 PM

I'll second Pat's suggestion about considering Strong for the light source. I haven't been disappointed with an Ultra-80 yet. Have safely run 5KW on 35mm film too (7KW on 70mm).

The best light vs heat I have come across is Kinoton though. It is the only lamphouse I would consider for say 16mm and 3KW (which we just installed)...you can put your hand in the projection beam (between the film gate and the lens even) and not feel uncomfortable after a minute.

As Pat said, throw really isn't a significant factor in light, unless you are close to pollution or live in a foggy area. About the only factor that will crop up is that at 141.2mm your f/stop will start increasing on standard lenses (thems the physics). If you are anticipating being in the 6 - 7" range, consider finding some B&L Super Cinephors (4" diameter)...they actually really work quite well for their age and are actually coated! I believe they have a typical speed of f/1.7 which, for a drive in, every little bit helps!

Steve

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"Old projectionists never die, they just changeover!"

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