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Author Topic: IMAX 3D Grey Patches Richard Hamilton Phenomenal Film Handler Posts: 1341 From: Evansville, Indiana Registered: Jan 2000 posted 05-05-2010 09:47 AM                     Anyone have any sources to buy some 8/70 black film, and what the average cost should be? As far as DTS, I think I installed 1 or 2 systems that the customer insisted on it. If I remember correctly, the DTS units chased our generated timecode. Rick  |  IP: Logged Cameron Glendinning Jedi Master Film Handler Posts: 845 From: West Ryde, Sydney, NSW Australia Registered: Dec 2005 posted 05-07-2010 07:03 AM                     I'm not sure if IMAX in NZ uses / has ever or still has IMAX shutter glasses but they too sometime caused similar issues if the sync transmitter plays up. Were the glasses like Real D sunglasses or space age looking thingies?  |  IP: Logged Andy Linde Film Handler Posts: 19 From: Nelson, New Zealand Registered: Mar 2010 posted 05-24-2010 07:12 AM                        The space age ones.  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 12-31-2010 08:33 AM                     The problem isn't film area, there's a lot of room outside the sprocket holes in 70mm. 70mm is the release film, the camera negative film is 65mm which has edges outside the sprockets similar to 35mm. The extra 5mm on the release film was for the magnetic sound tracks. The Imax 15/70 projector uses the rolling loop transport system through the gate. This system does not contact the image area of the film so a film can be shown thousands of times without image damage. In practice damage occurs in the storage reels and the picture dyes bleach out but one can run a film loop all day and not be able to see any scratches or marks in the image area. The edges take a beating though. There's a lot of surface wear on the "sound track" area both inside and outside the image area. Emulsion wears off fairly quickly (several hundreds of passes) so any data printed there photographically has a limited life. The Imax frame size was defined before any thought of digital sound so the frame lines are very narrow, and some Imax installations use so much film image area that the narrow ultrasonic splices are visible on screen. There was some thought given to having a narrow "bar code" printed in the frame line to identify the title and frame number allowing sound sync among other benefits but having this visible on screen would be nasty and the code had to be wider than was thought acceptable with the reader technology available. Experiments I saw with DTS code stretched it much like with 5/70-24 or 5/70-30 just more stretched. I don't know what print life they get, I wasn't aware there was any Imax 15/70 using DTS timecode printed on. Print life in Iwerks 5/70 systems using loop cabinets and Ballantyne projectors is limited by DTS data degradation from the emulsion wearing off. In my experience venues using DTS sound (this was unusual but they existed) the shaft encoder was used for DTS synchronizing. They used a converter box that generated SMPTE time code from the biphase shaft encoder to sync the DTS unit, no timecode data from the film. You had to set a sync frame in the projector and reset the timecode converter every show. Slugs still had to be spliced in to replace damaged film with this sound system.  |  IP: Logged

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