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Topic: Question regarding light output

Mitch Davis
Film Handler

Posts: 10
From: Montreal, Quebec
Registered: May 2000

posted 05-14-2000 11:30 AM

Got a newbie question for the group:

I'm about to be getting a home 35mm projector with a 1000 Watt lamphouse. The thing is, I live in an apartment, and 1K might be a bit too bright for a 32 foot throw! The guy selling me the projector told me to just power the light on low, but I just read that this will kill the bulb much quicker. I realize that I can always defocus the bulb for a dimmer light output, but for some reason, I feel strange about doing that. I'm thinking about just using a 500 watt bulb instead. The big question is, if I install a 500 watt bulb in a lamphouse designed for 1K, am I asking for trouble?

Cheers,

Mitch Davis

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 05-14-2000 11:43 AM

The rectifier may not turn down that much
Get a piece of stanless steel wire mesh(muchlike window screen) and place it between the lamphouse and the projector head.
Who are you buying it from?

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Mitch Davis
Film Handler

Posts: 10
From: Montreal, Quebec
Registered: May 2000

posted 05-14-2000 12:18 PM

I'm buying it from Robert Miniaci. He's the guru behind Robert Film Service, a supplier that services nearly every cinema and film festival in Montreal. The unit that I'm about to get is kind of a Frankenstein job of a Chinese portable, so to speak, as it's been modified from the bottom up. I'm just getting a bit uncomfortable with the notion of having such a bright lamp in an apartment. Am I wrong in thinking that 1K will be too bright from 30 feet? The last thing that I'd want to have is a unit that flares out its own image, or desaturates colours.

Cheers,

Mitch D.

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Scott Norwood
Film God

Posts: 8146
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99

posted 05-14-2000 01:48 PM

The necessary light output isn't determined by throw distance, but rather by image size. Whether you have a 20-foot throw or a 100-foot throw, you'll still need (roughly) the same light output to properly illuminate a given screen area.

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Mitch Davis
Film Handler

Posts: 10
From: Montreal, Quebec
Registered: May 2000

posted 05-14-2000 02:49 PM

In very (and I do mean VERY) rough approximation, a scope image would be about six feet tall and 15 feet wide. Not huge, but perfect for an apartment screening room.

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Brad Miller
Administrator

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

posted 05-14-2000 03:38 PM

You will be fine if you run it at 80-100% of it's rated power. That won't be too bright.

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Mitch Davis
Film Handler

Posts: 10
From: Montreal, Quebec
Registered: May 2000

posted 05-14-2000 03:48 PM

Really? Even when I'm projecting at 1:66 or 1:85? I'd always figured that 800-1000 watts of xenon would wash the colours out of such a small image. If it can be that bright, and still retain deep colours, it's going to look AMAZING!

I feel much, much better now.

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Brad Miller
Administrator

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

posted 05-14-2000 04:06 PM

You will have far more light with scope (2.35) than you will with conventional 1.66 or 1.85. If anything will be a problem, it will be scope. But it shoudn't be. You can always defocus the lamp just a bit if necessary.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 05-14-2000 04:43 PM

Be very crefull of any of the chineese portables as they are almost all junk and very light inefficient and har to get parts for
Also be wary of the supplier I sujest that you contact other theatres that have bought from them

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Mitch Davis
Film Handler

Posts: 10
From: Montreal, Quebec
Registered: May 2000

posted 05-14-2000 04:51 PM

Actually Gordon, RFS supplies allthe gear for two cinemas that I regularly work with as a programmer, as well as special outdoor projections for the World Film Festival. I've heard mixed things about the Chinese models too, but Montreal's biggest film lab, Covitech (formerly Astral) have one of these units in one of their projection suites. I've played with one, and it was more gentle on film than any of the other portables that I've seen (which granted, aren't many - Mignons and Ranger tones). I realize its a generalization, but are most of the Chinese portables unreliable? I'm getting a bit concerned.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 05-14-2000 06:59 PM

Mitch, Definately be careful. You could get a DeVry 35mm and be alot happier. I've never seen a portable that was any good at all. Ihave a pair of Russian machines that are copies of the Ziess portables and they are only so-so. I've had Tokiwas, Prevosts,and even a Norelco FP-4 and non of them were worth the money spent on them. I only have the russian machines because the price was cheap....250.00US for both machines. Where will you get parts for the Chineese machine? I know where you can get DeVry parts.
mark

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Scott Norwood
Film God

Posts: 8146
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99

posted 05-14-2000 07:15 PM

Oh, one more thought--if brightness really _is_ a problem (and it doesn't sound like it will be, given the specs that you list), you can always get a couple of stops' worth of ND (neutral density) filters at your local camera store and build some sort of bracket to hold them in front of your lenses...

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Greg Mueller
Phenomenal Film Handler

Posts: 1687
From: Port Gamble, WA
Registered: Jun 99

posted 05-14-2000 09:27 PM

I am running 1KW with a 25' throw and a 14' X 6' screen. Scope looks great.

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Mitch Davis
Film Handler

Posts: 10
From: Montreal, Quebec
Registered: May 2000

posted 05-14-2000 11:38 PM

Thanks to everyone for their kind replys!

I feel good about the 1K issue now, but I'm getting really hung up about everyone's bad experiences with portables. Has ANYONE had a portable that they found reliable and fantastic?? The Chinese unit that I played with a while back was incredibly forgiving with old, damaged film (I even watched it project a horribly irresponsible masking tape "splice" - without a hitch!), had a rock solid image and bright light output. The only thing I didn't like about it was the rectifier.

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Michael Barry
Jedi Master Film Handler

Posts: 584
From: Sydney, NSW, Australia
Registered: Nov 1999

posted 05-15-2000 12:04 AM

Mitch:

I've seen 2K lamphouses illuminate screens of roughly the size and throw that you describe with spectacular results. I don't think that 1K is out of the question (from what I gather).

A little too bright is a far better proposition than too dark (ahem!). If highlights flare or strobe then you can always cut back the current a little (as Brad suggested).

If you get a chance, try experimenting with different screen surfaces because that will have a huge effect on the image.

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