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Topic: Mirror Projection

Bernard Tonks
Jedi Master Film Handler

Posts: 619
From: Cranleigh, Surrey, England
Registered: Apr 2001

posted 07-01-2008 04:45 AM

quote: Ken McFall
Ok Yes it was a former ABC, Cannon, MGM and originally built by Star. It runs a lot of main stream art house stuff but none the less is a West End cinema charging top prices.

You were in fact correct in your original posting Ken long ago in 2003, that Cinecenta opened the Panton Street 4 screen site.

Periscopic Projection

Not mirror projection but many years ago I did some relief projection in a London Chinese restaurant and cinema where the projection room was separated from the auditorium by an illuminated corridor. Very strange doing the projection on changeovers with 2k reels. Projectors were Ross GC3 with RCA 9031 soundheads, and carbon Peerless Magnarc’s. Programmes were always double features with new prints and in scope without English subtitles. Adverts & Trailers were never shown.

Wages were above average rates with a trolley of food supplied daily at 6pm. My order was always roast chicken English style. What did amuse me was the amount of lettuce every time, enough to feed the rabbit population of the South of England I would think. [Big Grin]

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Paul H. Rayton
Expert Film Handler

Posts: 210
From: Los Angeles, CA , USA
Registered: Aug 2003

posted 07-04-2008 12:24 AM

(Original post deleted by author -- not really on the topic of discussion!)

There have been a few theatres over the years that have used mirrors for projection, for one reason or another. I recall one here in L.A. that had a bit of a size constraint, in that the theatre roof was rather low, and the projection room needed to be raised a bit (without necessarily enlarging the building), so the projection room had a set of downward-bouncing periscopes -- which are, really, just mirrors -- for each port (projection and observation).

The light would come out of the projector, hit the first mirror and be reflected 90°downward, and then hit the 2nd mirror, which would re-direct it back 90° toward the screen. The vertical gain was about, if I recall, only about 3 feet or less, but it allowed the picture to reach the screen OK.

I never liked working it (it wasn't exactly a key theatre, more like a neighborhood place), because, going through -- or off of -- all that glass, the image always looked a bit "milky" to me. And you had to see the image to focus it via similar periscopes in the observation ports, of course.

This was back in the '60s. Very excellent mirrors can be made, as long as they are "front surface", but then you have to be extremely careful cleaning them, because any abrasions will degrade the image quality. Yet eliminating all atmospheric contaminants completely is not really easy to achieve except by major filtration, so you'll have a perennial problem trying to keep 'em clean.

Another mirrored projection device, mentioned previously in this thread, was the "UltraVision" system, with the "Optiverter". This was developed in the early '70s, as I recall, when the industry was (theoretically) thinking "quality". The concept was two projectors were each aimed at a 45° angle (from the screen) into one box, with a combined, single light path from that one port to the screen. There were some other optical concepts involved beyond just that of the mirrors, but, if I recall correctly, the actual mirrors were enclosed in a sealed box, so the only glass to get exposed to air (and need cleaning) would be the optical port glass where the projector light went into the box.

The system worked adequately, but ultimately never caught on. Glenn Berggren was the key person associated with the process.

So, my suggestion: avoid the mirrors. (Unless, and this is really a big "if", you can find an old UltraVision box sitting around!). But even then ... probably still not a good idea.

[ 07-04-2008, 11:42 AM: Message edited by: Paul H. Rayton ]

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