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Author Topic: SCREEN SIZE ENQUIRY
Den Brown
Master Film Handler

Posts: 271
From: London, UK
Registered: Apr 2007


 - posted May 08, 2011 01:04 PM      Profile for Den Brown   Email Den Brown   Send New Private Message       Edit/Delete Post 
If an Elf NT projector is fitted with a long throw lens (F1.6 - 63mm), what size would the projected image be if the projector is 41 metres (134ft) from the screen?

Also, would this projector/lens combination give a bright enough picture from this distance?

.

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Michael O'Regan
Film God

Posts: 3085
From: Essex, UK
Registered: Oct 2007


 - posted May 08, 2011 01:15 PM      Profile for Michael O'Regan   Email Michael O'Regan   Send New Private Message       Edit/Delete Post 
H - 4.43M

W - 5.93M

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Wayne Tuell
Master Film Handler

Posts: 488
From: Minden, NV
Registered: Jul 2009


 - posted May 08, 2011 02:26 PM      Profile for Wayne Tuell   Author's Homepage   Email Wayne Tuell   Send New Private Message       Edit/Delete Post 
Den, does your projector use a XENON bulb or ELC bulb? That is asking a lot for an ELC using a f1.6 lens. Is there any ambient light that may interfere? Try a trial projection run before you invite a crowd to see if the image would be adequate.

I was told my old 1000 watt XENON was not enough for that distance...I don't know how true it is/was being I couldn't get private use of the drive-in anyhow to test it.

http://paulivester.com/films/projector/throw.htm

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www.16mmDrive-InFilms.com

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Michael O'Regan
Film God

Posts: 3085
From: Essex, UK
Registered: Oct 2007


 - posted May 08, 2011 02:38 PM      Profile for Michael O'Regan   Email Michael O'Regan   Send New Private Message       Edit/Delete Post 
Ah, thanks Wayne. I couldn't locate that chart. I tried to link to the chart on the efilm center page but I wasn't allowed for some reason.

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Den Brown
Master Film Handler

Posts: 271
From: London, UK
Registered: Apr 2007


 - posted May 08, 2011 02:41 PM      Profile for Den Brown   Email Den Brown   Send New Private Message       Edit/Delete Post 
Wayne,

Thanks for the tips. No, it's an ELC 250 watt lamp. The farthest I have projected from before with it was about 20 metres, so doubling that is a bit of a step.

May have to try to get closer to the screen somehow.

As for ambient light, we'll be outside with a 13% moon.

Michael, cheers for the dimensions.

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Jeff Taylor
Film Handler

Posts: 70
From: Chatham, NJ
Registered: Aug 2005


 - posted May 11, 2011 04:00 PM      Profile for Jeff Taylor   Email Jeff Taylor   Send New Private Message       Edit/Delete Post 
FWIW, I've seen some discussions about lumen output/throw distance/screen sizes on Film-Tech, which is largely populated by actual techs and projectionists (in addition to being the parent of this forum). Whether true or not, I have repeatedly read that throw distance is far less important than screen size in calculating required light output to achieve satisfactory results, which are defined generally as 16 footlamberts. By this theory, while the efficiency of the lens and the gain of the screen bear on the question, the total throw distance is less of a factor. Pay your money and take your choices!

--------------------
Jeff

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