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» Film-Tech Forum   » Operations   » Film Handlers' Forum   » Extreme keystoning

Author Topic: Extreme keystoning
Ken Lackner
Phenomenal Film Handler

Posts: 1883
From: Atlanta, GA, USA
Registered: Sep 2001

 - posted 07-30-2004 11:51 PM      Profile for Ken Lackner   Email Ken Lackner   Send New Private Message       Edit/Delete Post 
I have seen two movies in two seperate auditoriums in the last month or so at a local 20 plex, and both times the keystoning was horrible. This is a stadium seating facility. At most stadium theaters I've been to, the screen is pretty high off the ground. These screens were only a few feet (I'd say four) off the ground, and there was a lot of room between the top of the screen and the ceiling. That, combined with the fact that the port hole was only a few feet below the ceiling (I've seen them a lot lower at other theaters) made the keystoning so bad that the credits were actually curved.

I don't understand why someone would design a theater to have such an extreme projector tilt. Isn't there some SMPTE recommended practice on the projection angle? I wonder if that was taken into account when designing this theater.

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Mike Perju
Film Handler

Posts: 90
From: Toronto, Canada
Registered: Nov 2002

 - posted 07-31-2004 12:17 AM      Profile for Mike Perju   Email Mike Perju   Send New Private Message       Edit/Delete Post 
They most likely weren't thinking what they were designing... as usual. This is not unusual in "modern" multiplexes.

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Bobby Henderson
"Ask me about Trajan."

Posts: 10702
From: Lawton, OK, USA
Registered: Apr 2001

 - posted 07-31-2004 12:28 AM      Profile for Bobby Henderson   Email Bobby Henderson   Send New Private Message       Edit/Delete Post 
Sounds like pretty crappy theater design to me. Normally, in a large stadium house the screen may be angled upward a bit to provide a more direct target for the projector. Of course, the projector and console have to be mounted on some elevated and slanted platform to aim better at the screen.

It just sounds like this circuit did some real cookie cutter slap-it-together cheap design without actually doing any proper engineering.

This situation sounds just as bad (if not possibly worse) than the common dilema of keystoning in single screen theaters that were twinned. I've walked out of theaters and demanded refunds just as the trailers were starting to play when finding myself in an auditorium like that. If the projector is aiming toward the screen at any kind of angle (particularly a bad one when the port glass is near a corner in the room instead of the center of the wall) there's no way for the projector to gain any kind of focus. People just shouldn't have to watch movies like that at all. Only a fucktard bean counter could think that's okay to sluff off onto customers.

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Will Kutler
Phenomenal Film Handler

Posts: 1498
From: Tucson, AZ, USA
Registered: Feb 2001

 - posted 07-31-2004 12:35 AM      Profile for Will Kutler   Email Will Kutler   Send New Private Message       Edit/Delete Post 
In the all THX certified 20-plex (stadium seating) where I worked, horizontal keystoning was an issue.

In some auditoriums, the port window, audience and screen were not aligned to one another. On the smaller screns, the horizontal keystoning was somewhat noticable, but on a couple of large screens, not only was there keystoning, but due to the misalignment, although I was able to obtain the correct fl requirement, obtaining evenly illuminated screen was nearly impossible.

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Paul Mayer
Oh get out of it Melvin, before it pulls you under!

Posts: 3835
From: Albuquerque, NM
Registered: Feb 2000

 - posted 07-31-2004 01:36 AM      Profile for Paul Mayer   Author's Homepage   Email Paul Mayer   Send New Private Message       Edit/Delete Post 
Vertical keystone is very noticable at the theaters I frequent here. Both the Brenden Palms and Century Suncoast are really steep and it shows, especially when the current THX snipe is run. That blue border line ends up not being anywhere near parallel to the screen edges. It looks especially bad at the Suncoast with their slightly curved screens. Yuck.

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Robert E. Allen
Phenomenal Film Handler

Posts: 1078
From: Checotah, Oklahoma
Registered: Jul 2002

 - posted 07-31-2004 02:55 AM      Profile for Robert E. Allen   Email Robert E. Allen   Send New Private Message       Edit/Delete Post 
Years ago I worked the Granada Theatre in Ontario, California (a single screen with a high balcony) and the booth was about three stories up with the portholes about two feet above the booth floor. The screen was tilted up which minimized the keystone effect and movable side masking squared the picture. So even back then the designers knew how to compensate for it. Aren't they using theatre designers for the 'plexes today?

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Carl Martin
Phenomenal Film Handler

Posts: 1395
From: Oakland, CA, USA
Registered: Feb 2002

 - posted 07-31-2004 02:58 AM      Profile for Carl Martin   Author's Homepage   Email Carl Martin   Send New Private Message       Edit/Delete Post 
my very old theater has horrible keystoning on the main screen. formerly a single, now a triple. during a retrofit a few years ago, the flytower (yes, that old) was demolished, so the screen had to move in. the very back of the seating area was raised a little for ada reasons, which meant that to see the top of the screen under the former balcony overhead, the screen had to move down as well. it's very apparent on windowboxed trailers, but when there aren't obvious visual clues, the distortion isn't usually noticeable.


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Tim Reed
Better Projection Pays

Posts: 5244
From: Northampton, PA
Registered: Sep 1999

 - posted 07-31-2004 09:11 AM      Profile for Tim Reed   Author's Homepage     Send New Private Message       Edit/Delete Post 
quote: Bobby Henderson
Of course, the projector and console have to be mounted on some elevated and slanted platform to aim better at the screen.
Usually, that's a case where the architect didn't know how to spot the portholes properly, and they have to get up and over the bottom of the window frame with the machine. Most consoles will tilt downward far enough for a pretty steep angle; it's just that the porthole has to be close enough to the floor for it to work.
quote: Robert E. Allen
Aren't they using theatre designers for the 'plexes today?
There aren't too many people around anymore who really know the score. Most new builds I was involved with, the architects didn't know from their rear-ends how to locate a porthole, or how to plot sightlines. If I was on the job early enough I could spell it out for them, but unfortunately, that was the exception.

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Frank Angel
Film God

Posts: 5198
From: Brooklyn NY USA
Registered: Dec 1999

 - posted 07-31-2004 10:40 AM      Profile for Frank Angel   Author's Homepage   Email Frank Angel   Send New Private Message       Edit/Delete Post 
One of the worst retros I have ever seen was a local single screen that was quad-ed -- two screens in the original orchestra and two screens in the balcony, with a wall sliced right down the middle.

For the two balcony rooms, they just used the original seats and the same booth ports. This put the ports for each theatre in the topmost extreme corner, making the keystone this bizarre thing where the credits would dip to the one corner at the bottom of the image as if the projector wasn't level but as they crawled to the top would wind up higher, making it look like the projector was not level in the other direction.

As if that weren't bad enough, the screen was now centered in the "new" theatre but that was off-center to where the original screen had been. Problem was, they never install new seating....they just left the old seats as-is and of course that meant that they were aimed, not at the new screen, but at the imaginary old screen. So there you sat, pointed in the wrong direction.

The separation wall was straight while the original wall was angled and of course the floor was steeply raked and the ceiling also raked with a design that still pointed to an imaginary, nonexistent centerline. It wound up that every visual cue in the room was slightly off-center and tilted. It made you feel like if you didn't grab onto some solid railing or seat back you'd not be able to maintain your balance and you'd just fall over.

Cutting the theatre in half made each new balcony "theatre" a long, LONG narrow room with the screen still located on the stage but now with a "roof/floor" added from the front of the balcony to the screen, putting the screen literally the distance of the orchestra to the front of the balcony. This made it impossible to sit any closer to this new small screen than the entire length of the orchestra. If you sat in the back of the room, the screen looked like a postage stamp.

Did I mention that this long narrow room was not acoustically treated in any way whatsoever, so as far as speech intelligibility goes, if there were a number to measure it, it would be negative 100. You couldn't understand not a word that was being spoken....all you heard was echo. My girlfriend and I watched our first and last film there -- BLUE LAGOON -- luckily it was so bad that it was better if you didn't understand what they were saying.

And that, boys and girls, is an example of theatres DONE WRONG.

It is now a bank.

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Edward Jurich
Master Film Handler

Posts: 305
From: Las Vegas USA
Registered: Jul 2003

 - posted 07-31-2004 07:11 PM      Profile for Edward Jurich   Email Edward Jurich   Send New Private Message       Edit/Delete Post 
Usually the old movie palaces had very high booths but also a long distance to the screen. The long distance helped reduce the keystone. A high booth and a large screen a short distance away is really really bad. Some of the auditoriums at the AMC here have really bad distortion from keystone and a curved screen

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Bryan Fournier
Film Handler

Posts: 61
From: Greensboro, NC
Registered: Dec 1999

 - posted 08-01-2004 12:03 AM      Profile for Bryan Fournier   Email Bryan Fournier   Send New Private Message       Edit/Delete Post 
Don't you just love those old "bowling-alley" auditoria.

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