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Author Topic: What is the proper loop size for a Century projector? Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 05-07-2008 06:50 PM                        The geometry on the C and the SA is the same, so loops would be the same. Remember the size of the lower loop is your only opportunity to adjust the optical sound/picture sync. Tight loops for very long throw houses; the reverse for short throw. When we did a large number of premieres in the 80's it was common to find that even very experienced people made the loops WAY too big. Gunshots were "delayed." Louis  |  IP: Logged Kenneth Wuepper Phenomenal Film Handler Posts: 1026 From: Saginaw, MI, USA Registered: Feb 2002 posted 05-07-2008 08:20 PM                     Most present threading leaders have a built in sync check for the sound threading. When a number is in the gate and at the aperture behind the lens, the diamond should be at the slit of light in the reader. The amount of film between these limits will be your determining factor in proper threading. I usually count the number of frames in the loop below the intermittent and place that information on the projector casting for future reference. The upper loop will also determine sync of the digital sound if it comes from an upper reader. The number of frames in the path from the upper reader to the analog slit must be consistent or there will be some nasty sounds when the digital reverts to out of sync analog. KEN  |  IP: Logged Robert Throop Master Film Handler Posts: 412 From: Vernon, NY USA Registered: Jun 99 posted 05-08-2008 09:11 AM                     If I'm not mistaken the diamond on the leader is 20 frames ahead of the number. Dead sync is 21 frames which would be correct for a drive in. 20 frames would be right for someone sitting about 40 feet from the screen. very large houses require a smaller loop. Bob  |  IP: Logged Michael Moore Expert Film Handler Posts: 188 From: Dover, DE / USA Registered: Jun 2006 posted 05-08-2008 09:26 PM                        You know I never really paid overly too much attention to the size of the loop other then make it so it was not to big or not to small. My rule of thumb is that if I look directly at the loop the film splits the oil window on the intermittent housing perfectly in half. I do this with the frame knob dead center (as close as possible) and just make sure the intermittent is in the dwell position. I also have never had delays or sync issues with sound, even if the loop is too big or too small then again our house is only an 80 foot throw. I find on the SA Century I have if I use the pad rollers as a guide the loops are too small. I find the top is about one sprocket hole bigger then what the pad roller makes, and the intermittent is about 3 sprocket holes bigger. Mike  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 05-08-2008 11:15 PM                       Robert, the optical track for 35mm is advanced 20 frames ahead of the picture.  |  IP: Logged Jeffry L. Johnson Jedi Master Film Handler Posts: 809 From: Cleveland, Ohio, USA Registered: Apr 2000 posted 05-10-2008 01:47 PM                        Robert is correct. SMPTE 40, "SMPTE Standard for Motion-Picture Film (35-mm)-- Release Prints--Photographic Audio Records" specifies 21 frames +/- 1/2 frame. The projection leader indication of twenty (20) frames places sound/picture synchronization about 50 feet away from the screen.  |  IP: Logged

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