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Author Topic: Off-center projection and keystone mitigation Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 09-22-2015 11:20 AM                        quote: Steve Guttag With Christie, the tilt of the projector has an effect on the xenon lamp since it is tilting along with it. With NEC and Barco, tilt does not since the lamp remains parallel to the floor. Wow, that sure is good to know. I guess we won't be using Christie when we finally go digital. We have the typical (and all too common) single screen problem -- a booth 5 stories up and projectors at a massive downward tilt -- so severe that there are two-by-fours under the ass-end of the pedestals and we had to put those special Simplex brackets on the XLs' takeup magazines so as to tilt the magazine forward enough that it clears the floor and doesn't get crushed into the floor like a bug when you crank the pedestal tilt wheel down. Our screen, when it flys in, is also tilted bottom forward to compensate as much as possible for keystoning. I guess putting a Christie in would be ill-advised, eh?  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 09-22-2015 02:48 PM                     Christie 2210/2215/2208 are ok, lamps are parallel to the screen.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 09-22-2015 02:58 PM                        Even if you get a "perfect" picture using lens shifters, the reflection off the screen will suffer just like it did in 35mm. Maybe with digital there is an opportunity to reduce or eliminate being "off." The goal is to get a undistorted picture AND put the reflected light into the center of the best seating area. This is even more important (required?) when using silver screens or any high gain screen.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 09-22-2015 03:57 PM                     Would tipping the top of the screen back a few degrees help any? This was an old practice for wide palaces with average throw lengths to reduce keystone being the booth was above the balcony.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 09-23-2015 05:51 AM                        Yes. These things will never change. The information may be forgotten, however.  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 09-23-2015 07:25 PM                        Yes, Monte, that's the same as what we do, but we tilt the bottom foward; the top of our frame is chained to the fly pipe. Same effect, you are compensating a bit for the keystoning. But of course, with these severe angles, you can't fully correct it, nor would you want to, given you would then be directing much too much of the light up into the ceiling instead of the audience. The only way you can get away with this cheat is if you have a matte, 0-gain screen. I can't imagine what a horror-show you'd create trying to do that with a silver screen or even a mild gain screen. I am afraid if we want 3D in this house, we are going to have to go with Dolby or it's 2D only. There is also the Omega color interference system -- same as the Dolby concept, only they use a 5 band color comb filter for each eye instead of the 3 that Dolby uses and that eliminates needing to color correct the two images. BUT, their downfall is that this system is only available for a dual projectors. They've yet to offer a filter wheel; you have to have two projectors or nothing. On the plus side, their glasses are much less expensive than Dolby's. Not much of an economic relief if you initially have to buy a second projector. It would be a great system if they got their act together and offered a filter wheel for a single projector system.  |  IP: Logged Stephan Shelley Jedi Master Film Handler Posts: 854 From: castro valley, CA, usa Registered: Nov 2014 posted 09-23-2015 07:51 PM                     There is also the expand system that uses the active glasses. No silver screen needed. Much more light efficient than the Dolby one. Glasses are even more expensive than the Dolby ones. And have batteries too.  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 09-23-2015 08:12 PM                        That ought to make for an intersting budget proposal for our 2500 seat house.  |  IP: Logged Stephan Shelley Jedi Master Film Handler Posts: 854 From: castro valley, CA, usa Registered: Nov 2014 posted 09-23-2015 09:17 PM                     Even the Dolby glasses at around $10.00 each is good budget item.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 09-24-2015 06:35 AM                     Ah but the Dolby (or XpanD) glasses are a recycle item (so you need to thing of the washing equipment too. That said, if you do the math on their use life cycle, it is a pretty cheap 3D show. However, with a 2500 seat venue, you also need to RECOVER those glasses (more so with XpanD) or running 3D gets VERY expensive. Note too, with the 6P laser projectors, you have your option of single projector (Barco) or dual projector (Christie)...then the Dolby light efficiency shoots to the top of the pack since no filter wheel is required (and sucking light...filters only take away, never add). But seriously...3D? How many anticipated shows would you have to justify any system?  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 09-24-2015 12:39 PM                        Not enough to justify even suggesting such an expense. We are still floundering being able to justify installing digital at all. It's just that if I were king and could wave my hand and get anything I wanted, of course I would I'd want a booth to be capable of running most any format. You don't want a booth that can't run everything from 16mm with our trusty Eastman 25B to 70mm to digital. I certainly would not want to have to say, oh we can't run a 3D title if a film professor came to me and wanted to show THE HOUSE OF WAX to his class (or I wanted to have a pizza and movie party and show AVATAR to the staff for one of our private midnight shows as we have every so often). Look, I wanted to swap out our XLs to JJs but couldn't honestly even justify that expense as much as I wanted it so badly. Everyone has to live with the limitations you're dealt.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 09-24-2015 02:29 PM                     quote: Steve Guttag But seriously...3D? How many anticipated shows would you have to justify any system? (Can we add Barco Escape into this equation?)  |  IP: Logged David E. Nedrow Master Film Handler Posts: 368 From: Columbus, OH, USA Registered: Oct 2008 posted 10-02-2015 07:43 PM                        I think we're now at the point of deciding whether to expand the projection platform slightly or build a projector enclosure in the theatre itself. The latter would allow the projector to be on the centerline horizontally, and closer to the vertical centerline. And maybe less expensive that the platform alternative.  |  IP: Logged

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