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Author Topic: Desiging a curved screen for a 2-projector setup Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 04-12-2007 10:04 PM                        Not for changeover, but for one digital and one film, each offset 2'6" from the centerline. What's the best way to establish an optimum curvature for a gain screen (1.4) which doesn't result in excessive side distortion?  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 04-12-2007 10:19 PM                     It will be the same ray tracing but you will want it based on the projectors on center line. If you only had one projector then the screen would be effectively angled towards that one projector (not the same degree as the offset but so the light is reflected best back onto the audience). Steve  |  IP: Logged Kyle Anderson Film Handler Posts: 86 From: Tyler, TX, USA Registered: Dec 2005 posted 04-12-2007 11:47 PM                     Though it's annoying up in the booth, you can install tracks on the floor and have both projectors going through the same porthole (just move one over out of the way); it can be done well if you do it right, and it can save a LOT of money trying to adjust a screen for 2 projectors. long tracks are a must ( > 10 feet) so threading isn't a royal pain in the ass.  |  IP: Logged Phillip Grace Expert Film Handler Posts: 164 From: ACMI. Melbourne. Australia. Registered: Mar 2004 posted 04-13-2007 02:34 AM                     How about trying to find some way of stacking the projectors so that both beams are along the vertical centre-line of the screen? What is the shape and size of the digital projector? You could stand a small on on end in front of the 35mm machine and use an angled mirror to divert the beam. There may also be a partial solution to sidewise distortions using lens shift for both film and digital projectors.  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 04-13-2007 04:01 AM                        quote: Steve Guttag It will be the same ray tracing but you will want it based on the projectors on center line. You mean traced as if the light came from a "phantom projector" dead center? Does that still give you a fairly even spread (I would think that the left projector would illuminate the audience more right of center, and the other way around, although that may not even be noticeable to the naked eye)? Do you prefer to curve on a radius around the lens or so that the light is concentrated into a spot in the back half of the auditorium?  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 04-13-2007 08:36 AM                     Yes, based on a phantom projector and yes, the left projector will light to the right more and the left projector will light to the left a bit more...not horribly so...you are only talking about a 2.5' offset over how long a throw? I curve the screen so the maximum light is reflected back onto the bulk of the audience. Curving based strictly on the throw really can't use a gain screen or hot spotting will result. Steve  |  IP: Logged

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