Film-Tech Forum ARCHIVE: Mirror Projection

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Posted by Michael Dolan (Member # 4808) on 06-22-2008, 03:47 PM:

Ok so some guys were here again today going over stuff for our two Digital projectors we have coming in. My question is the two theaters that are getting the digital they are trying a side by side deal with the digital and 35mm but we don't really have the space. They were talking about putting the 35mm behind the digital facing to the side and using a series of mirrors to project the image to the screen. I have never seen this done and want to know what that even looks like.

Does anyone have any pictures of something like this? and does it change the quality of the picture or the way it runs?

Posted by Mike Schindler (Member # 1309) on 06-22-2008, 04:23 PM:

Check out the pictures of the Ogden 6. From what I understand, it eats a lot of light.

Posted by Joe Redifer (Member # 3) on 06-22-2008, 05:37 PM:

Sounds like your guys are more interested in making some money from the sale and install than they are with the quality of the presentation.

Posted by Richard May (Member # 2627) on 06-22-2008, 06:16 PM:

It's also just another way for them to make [dlp]

look better than film. Mirrors suck.

Posted by Frank Angel (Member # 248) on 06-22-2008, 08:39 PM:

Mirrors get dirty, mirrors get MOVED. There is a reason why 35mm projector heads are mounted on humongously heavy pedestals and consoles -- so they don't get jarred around. How are those mirrors going to be mounted and with what kind of rig that would allow fine adjustment of the mirrors so that all the corners on the screen are at perfect right angles without any distortion? What's going to stop that rig from being bumped and ALL the hours of alignment shot to hell? And believe me, it will take hours to get it right....or sort of right, which is about the best you can expect.

I once participated in such a folly (it wasn't my idea) and it went down to a quick and ignominious defeat. Do yourself a favor...say NO THANK YOU.

Posted by Kenneth Wuepper (Member # 1174) on 06-22-2008, 09:27 PM:

Years ago, 1960s, the Bush Film and Equipment Company here in Michigan manufactured an interesting classroom projection system. There was an RP screen on a slide out box at the front of the machine. Beneath the slid out screen were speakers for the sound. Inside was a Kodak Pageant projector mechanism and a custom built amplifier for the sound. The reels of 16mm film could stick out of the box through coverable slots. 1,600 feet of film MAX! The lens was very wide angle and projected to a front surfaced mirror and then to the back of the RP screen. The system worked pretty well as there was less need to darken the room and the mirror reversed the image for the rear projection to look right from out front. The mirrors were very costly and could be dulled by improper cleaning or scratched by wiping dust across the surface. I doubt that two such mirrors would produce satisfactory results for theatre use.

KEN

Posted by Frank Angel (Member # 248) on 06-23-2008, 04:28 AM:

There was a theatre on Flabush Ave in Brooklyn of which I only have a vague recollection of the name, possibly the Avon? It closed soon after I got here, but what I do remember was that it was the only theatre I have ever heard of that used an RP screen instead of front projection. The presentation quality however is vividly etched into my memory as it was horrific.

Evidently getting the image big enough required a severe wide-angle lens which gave barrel distortion and when combined with the RP screen caused a terrible hot spot in the middle of the screen. The multiple mirrors themselves added to the distortion. And of course the RP screen precluded putting speakers behind it. Plus, the sound of the projector could clearly be heard. Were there change-overs? How do you do change-overs with mirrors? Possibly place the projectors facing each other and project both beams into a prism? This was in the early 70s so I assume platters weren't common yet.

Although I never saw the setup, I was told that in order to get the picture a descent size, they had to fold the image a few times due to the limited space behind the screen, with each mirror needing to be bigger and bigger, distorting and dulling the image more. They couldn't do CinemaScope with this setup as the fall-off on sides would be too extreme. I can't imagine how difficult it must have been to align multiple mirrors.

Posted by John Wilson (Member # 269) on 06-23-2008, 05:15 AM:

I ran mirrored projection in the old Penrith 1+2 in the late 80's. The original mirror had imperfections which looked very bad when magnified. They replaced the mirror and it looked OK...but it wasn't a very big screen so that may be why it looked OK.

If they're going digital, why keep the 35mm? If there's no room, then there's no room.

Posted by Phillip Grace (Member # 2262) on 06-23-2008, 05:19 AM:

Hi Michael.
That proposed arrangement really sounds like doing it the hard way! It would make more sense to me to install the digital projector sideways near the front wall of the booth and use a single mirror at 45 degrees to turn the image and shoot it out through the projection port alongside the 35mm image. It should be possible to flop the image over electronically at the projector, as is done for rear projection. Only one reflecting surface to lose light etc. Diverting the light beam from the 35mm projector as described will be harder to do, require larger mirrors and projection ports, and degrade what should (still) be the better motion imaging system.
How big is the digital projector? How small is the booth?
Cheers.
Phil.

Posted by Andy Frodsham (Member # 4061) on 06-23-2008, 06:24 AM:

In the early seventies when some of our larger old cinemas were divided-up to make smaller theatres, the installers always tried to contain all the projection equipment in a single booth. This often resulted in some of the theatres receiving the projected image via a periscope type system; some directly. Audience members in the know would always try to book seats in the theatres which had 'direct' projection - the picture via mirrors looked crap!

I remember in the mid seventies seeing THE EXORCIST projected via mirrors into a small auditorium of a, once large, London cinema (A Warner theatre, I think). I also recall that the very wide beam of light emerging from a mirror in the rear wall was quite distracting!

In a projection setup I would avoid any mirrors like the plague!

Posted by Mark Gulbrandsen (Member # 72) on 06-23-2008, 07:20 AM:

Personally I would not use these guys for your install! What they have come up with is a joke. I recommend that you install a second port for the digital stuff, a port is far less expensive than the front surface mirrors you will need to go the mirror route. If you are lucky enough to get Christie gear all the operator controls are at the rear. Installing wheels on the base would allow you to retract the projector back to do a lamp change. Pretty simple really... although in all instances of having done this for our customers the film gear has never been used again... I recommend that you research what you are purchasing and the guys you've hired very thoroughly before you ever go to the next step... To me it sounds like you are getting digital gear that has to side mounted operating touch panels.

Mark

Posted by Andy Frodsham (Member # 4061) on 06-23-2008, 08:04 AM:

I suppose it's a kind of back-handed compliment to 35mm! They know that 35mm will (to some extent) handle being projected via a mirror - although it will end-up looking crap. The digital stuff couldn't cope with mirrors - it looks crap to start with!

Posted by Mark Lensenmayer (Member # 134) on 06-23-2008, 02:51 PM:

Some of the early (70's era) AMC installations used mirrors in every auditorium. The projection rooms and auditoriums were on the same floor, so they did not have to go to the expense of putting in a second floor. They used a mirror system (2 front sided mirrors) to "periscope" the image about 8' up so it cleared the heads of the patrons.

Posted by John Wilson (Member # 269) on 06-23-2008, 05:50 PM:

quote:
The digital stuff couldn't cope with mirrors - it looks crap to start with!

Not the digital shows I've seen.

Posted by John Walsh (Member # 168) on 06-23-2008, 05:53 PM:

I agree with everyone above, especially Joe; only really crappy theaters would use mirrors. What about that 'image mover' system MIT makes to slide projectors left/right on tracks?

Posted by Gordon McLeod (Member # 33) on 06-23-2008, 08:23 PM:

I beleive BACP was the first with a track system for 2 machines

Posted by Jim Cassedy (Member # 4115) on 06-24-2008, 05:41 PM:

During WWII, most large cities had a theater operated by a company called TELENEWS. These places ran nothing but newsreels 24/7.

Most of these theaters were small venues, some them were actualy built into vacant stores, and to maximize space they used rear projection in most of them.

I've seen photos of two TELENEWS booths. One of them showed two projectors facing each other and shooting into a mirror device solidly mounted on a projector pedestal between them.

The other TELENEWS booth photo I've seen showed 2 projectors with intetrated "right-angle-lenses", simlilar to the ones Bell & Howell used to sell for 16mm projectors.

In the late 1970's I recall working several UA change-over booths out on Long Island, NY that had a periscope arrangement like someone else mentioned here to shoot projection beam over the heads of the audience.

Most of these 'submarine booths' had a window at eye-evel so you could see the cue marks, but I recall one place that becuase of the way it was designed, you had to look up into a mirror mounted at a 45deg angle above your head to and watch an upside down and backwards screen image to see the cue marks!

That was a real mind-f..k!

Posted by Richard Fowler (Member # 893) on 06-24-2008, 07:21 PM:

I was doing track systems way before those guys, some motorized with limit switches and locating pins [Razz]

I had done some mirror jobs which where at the mercy of the operating staff...best to avoid [Smile]

Posted by Michael Dolan (Member # 4808) on 06-29-2008, 02:35 PM:

It seems now they are going to put in 2 digitals keeping only 1 of them doubled up with a 35mm. I believe we have also whined enough for them to put it on a track system. So hopefully we have burried the mirror idea 6ft. under [thumbsup]

I guess only time will tell

Posted by Ken McFall (Member # 845) on 06-29-2008, 03:55 PM:

London's West End still has a four screen cinema, Odeon Panton Street, that uses periscope projection in all screens.

The observation port being at low level in respect to the projection mirror. The pictures are very small with long relative throws so the image is not too bad. Considering the importance of Leicester Square and the public perception of quality linked with ticket price it is amazing that it is still around today.

I know the booth quite well and to say it is a dump is putting it mildly. The equipment is a disgrace, with many many long standing faults, and the working conditions are very poor.

But front of house there is a bit sign declaring ODEON "Fanatical about film".... should add to that "but not about the projection equipment or working conditions" £9.50 to pay to see sub standard projection in the heart of the West End is a joke.

I agree with John...

"only really crappy theatres would use mirrors"

Posted by Ben Wales (Member # 92) on 06-29-2008, 04:14 PM:

quote: Ken McFall
I know the booth quite well and to say it is a dump is putting it mildly. The equipment is a disgrace, with many many long standing faults, and the working conditions are very poor.

That Cinema was once a former ABC Cinema, you are getting confused with the main Odeon Cinema's in the Square as at this site programming is a mixture of Art House and extended weeks (2nd)run from other Odeon sites.

Perhaps you should write to the Odeon Technical Depatment with your views about this Cinema Projection equipment?, or just wait for a few years as Odeon have announced at last week's Cinema Expo in Amsterdam that they are going all D-Cinema within the next few years.

Posted by Ken McFall (Member # 845) on 06-29-2008, 04:25 PM:

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.

As for writing to the company.... if a major player in the game cannot see for itself the condition of one of it's prime sites what does that tell you.

Knowing what I do I certainly would not go and see a film there or indeed any periscope projection show. Clapham Picture house included.

These shows charge top rate for poor quality.... which is what this post is all about. Avoid mirror projection at all costs.

While I remember, The Odeon Kensington used to. may still have, have two screens that used right angle mirror projection. The projectors were Vic 8's adapted so the film was laced soundtrack in. The screens were un-perforated with the speakers below the bottom picture line. It was quite strange initially but you got used to lacing 'wrong' way round. Picture quality was quite good but that may have been a compensating effect of the un-perforated screens.

Posted by Scott Norwood (Member # 30) on 06-29-2008, 05:47 PM:

There's a theatre in Washington DC (Dupont Circle?) that uses periscopes. The auditoria themselves are smaller than most living rooms and it isn't exactly a top-quality venue. I'm sure that Steve G. knows the details of this place and could post additional information if he chooses.

The Brattle Theatre in Cambridge, MA. uses a rear projection system like the newsreel houses described above. The 35mm projectors face each other and there is a pair of 45-degree front-surface mirrors between them to reflect the image through the (huge) port glass and onto the screen. Masking is manual and is located in front of the screen surface. Image quality is "OK," but not great. It improved significantly when the old screen was replaced in the early 2000s with a newer seam-less (in theory, anyway) screen.

Posted by Alan Plester (Member # 852) on 06-30-2008, 05:09 AM:

My cinema had one large booth and used the periscope system for the screen upstairs. When the mirrors got warm the picture was horrible and needed constant framing and focus. The mirror was float glass and was changed within 4 years result, just the same horrid presentation, always out of focus and like a head choppers ball. Please if you can AVOID at all costs.

Posted by Robert Throop (Member # 61) on 06-30-2008, 08:17 AM:

In the late sixties and early seventies there was a development program known as Ultravision. Among other things they had two projectors toed in and shooting in to a mirror box they called an optiverter. This converted each projector to centerline projection.
Bob

Posted by Steve Guttag (Member # 268) on 06-30-2008, 10:48 AM:

Scott,

The Dupont in Washington DC has finally shut down. Yes, it did use periscopes on most screens. The reasons were due to lack of booth space (couldn't build platforms that would be OSHA safe) and the need to project over hallways.

As others have said, periscopes should be one's last resort. One must use 1st surface mirrors of the highest quality (and they are not cheap). Otherwise, you are going to have issues with multiple images that often show themselves as soft or smeared images. It CAN be done, however.

As to the Dupont...due to the space issues, the walls were built rather thin on the projection room. The pariscopes were affixed to the booth walls (and floor). As such, when the booth door closed (or if anyone leaned/banged on a hallway wall), the image would move rather violently in the theatre. Oh yes, this theatre had a lot of "charm." Altec A8Cs were used because they "fit." That is, the theatre had wrap-around screens that stood about 18" off the wall...the A8s just barely fit behind there. I truely detested the Dupont 5.

Steve

Posted by Martin McCaffery (Member # 37) on 06-30-2008, 11:06 AM:

quote: Scott Norwood
There's a theatre in Washington DC (Dupont Circle?) that uses periscopes.

As Steve pointed out, it was the Dupont 5, not the gone but not forgotten original Dupont Circle theatre.

As I think I mentioned in other strings, right up the street from the old Dupont, the Janus 3, now closed, had a mirror system to get around the pillar in the middle of the auditorium. Also, the Cerberus 3, also gone, in Georgetown, had a mirror system that projected down -- you could not see the screen from the booth, you had to focus in the mirror. Neither of these theatres were known for fine projection. The Town theatre on NY Ave had a periscope system because it was on the 3rd floor and the booth was too far back in the balcony to clear the edge and hit the screen.

I don't know if DC was particularly fond of mirror systems, or if it is just the "make-do" attitude when putting theatres into spaces designed for something else.

Posted by David Graham Rose (Member # 1450) on 06-30-2008, 11:30 AM:

Quote "
While I remember, The Odeon Kensington used to. may still have, have two screens that used right angle mirror projection. The projectors were Vic 8's adapted so the film was laced soundtrack in. The screens were un-perforated with the speakers below the bottom picture line. It was quite strange initially but you got used to lacing 'wrong' way round. Picture quality was quite good but that may have been a compensating effect of the un-perforated screens. "

Greetings

They were Vic 9's not 8's.

David

Posted by Ken McFall (Member # 845) on 06-30-2008, 12:18 PM:

Quite correct.... good to see you're paying attention.

Posted by Benjamin John Doman (Member # 4365) on 07-01-2008, 01:04 AM:

Hi,
If I remember correctly, the old ODEON Aylesbury screens 2&3 not only had mirrors, but were rear projection. The box was in the old front stalls, with the projectors pointing to (if you imagine) the front stalls exit doors on to a mirror which bounced the picture back onto the screen. Screen 1 in the old circle was unusual in that the screen was suspended with no wall to block off the front half of the cinema, and you could look over the circle front and see the old front stalls.

Posted by Bernard Tonks (Member # 809) on 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]

Posted by Paul H. Rayton (Member # 1817) on 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 ]