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Author Topic: Maximum shrinkage able to be screened? Carl Martin Phenomenal Film Handler Posts: 1424 From: Oakland, CA, USA Registered: Feb 2002 posted 08-11-2004 05:24 AM                        i'm pretty handy with the "artsy-craftsy" method, but i'd love to have a perfix machine or cinebug. i've got a reel with 45' of stretched sprockets on it and i'll be damned if i'm going to pore over that inch by inch. carl  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 08-11-2004 07:21 AM                     I always imagined preservation specialists had special "shrunken sprockets" for just this problem. No? --jhawk  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 08-11-2004 07:37 AM                        As I noted, intermittent sprockets for 35mm nitrate film which had considerable shrinkage during processing had a 0.935 inch base (root) diameter. Modern sprockets usually have a slightly larger base diameter, typically 0.950 inches. Standard is SMPTE 242 The sprocket tooth pitch is measured at the midpoint of the nominal film thickness: Pitch = ((Root Diameter + Film Thickness/2) x Pi)/(Number of Teeth)  |  IP: Logged Thomas Procyk Phenomenal Film Handler Posts: 1842 From: Royal Palm Beach, FL, USA Registered: Feb 2002 posted 08-11-2004 10:03 AM                     Cinemeccanicas are also generally good with shrunken prints. I ran a badly shrunken acetate print (top and bottom frame lines visible almost all the time) which was heavily lubricated, and it ran just fine on a Victoria 8. The film was twisting like a party streamer on its way to and from the platter. Maybe I'll run it again one day and take some video. A sight to see. =TMP=  |  IP: Logged Carl Martin Phenomenal Film Handler Posts: 1424 From: Oakland, CA, USA Registered: Feb 2002 posted 08-11-2004 01:47 PM                        quote: John Pytlak The sprocket tooth pitch is measured at the midpoint of the nominal film thickness: Pitch = ((Root Diameter + Film Thickness/2) x Pi)/(Number of Teeth) since the diameter of the sprocket + film includes 2 thicknesses of film, shouldn't it be Pitch = ((Root Diameter + Film Thickness) x Pi)/(Number of Teeth) ? carl  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 08-11-2004 02:02 PM                        I looked up the standard, and you are correct.  |  IP: Logged Thomas Jonsson Expert Film Handler Posts: 216 From: Bromolla, Sweden Registered: Sep 2003 posted 08-11-2004 02:52 PM                       Mark I´m just curious, how long is the film gate on the Brenkert BX-80? Thomas  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 08-11-2004 06:13 PM                        Leaving aside the issue of dealing with shrinkage in the context of archival preservation, I agree that the characteristics of the projector being used are a key factor in determining what you can get away with in projection. Obviously, pitch/width of sprocket teeth and gate pressure are the main things. An FP-20 would always be my mechanism of choice for running significantly shrunk 35mm prints on account of its small teeth and the insanely low gate pressure which which it can project a steady image. Using a shinkage gauge, standing orders at the only cinema I've worked at which was licensed to show nitrate were that 0.6% was the maximum permissable. For info, the National Film Preservation Foundation's Preservation Guide advises that: quote: Page 15 of manual Once a 16mm or 8mm film has shrunk beyond 0.8% (1% for 35mm), it may be damaged in projection. Beyond 2%, even skilled laboratories can have trouble copying the film. At this point the film generally exhibits additional decay problems beyond shrinkage. For a cinema which regularly shows older prints, a 'shrinkometer' might be a useful thing to have in the booth. Although you get used to what your projectors can and can't safely deal with over time, having a percentage figure for a given print would help in replacing some of the gut instinct with hard data...  |  IP: Logged Josh Jones Redhat Posts: 1207 From: Plano, TX Registered: Apr 2000 posted 08-12-2004 02:00 AM                        I hate to toot my own horn, but the brenkerts are pretty incredible when it comes to running damaged/shrunken film. I have a small roll of film I call my 'can your projector do this' reel. I doubt it would run through the machines at work, but runs through mine just fine. Runs gooky nitrate as well Part of their saving grace is CS like sprokets that every brenkert I've ever seen had. much more tolerance for slop in there. For the record the gate in my BX-100 is 5 7/16" long (from the top of the loop 'horns' to the start of the intermittant shoe.) Josh  |  IP: Logged Daryl C. W. O'Shea Film God Posts: 3977 From: Midland Ontario Canada (where Panavision & IMAX lenses come from) Registered: Jun 2002 posted 08-12-2004 02:51 AM                        Same here Josh. We used to have a few beat to hell, brittle, half the sprockets missing, Christmas cartoon reels that would run through BX-60s just fine, but didn't have a snowballs chance in hell going through a Simplex or Century.  |  IP: Logged Dan Lyons Jedi Master Film Handler Posts: 698 From: Seal Beach, CA Registered: Sep 2002 posted 08-12-2004 04:28 AM                     damn.. I need to take a pic of my "torture loop" that I ran through my Pro35 a few dozen times. Just for fun I made a loop of old brittle acetate, then i took a foot or so of the sprockets off one side with scissors! Yes it ran through without breaking. Update, here is the pic. This only shows half of the sprocketless film. [ 08-12-2004, 02:57 PM: Message edited by: Dan Lyons ]  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 08-12-2004 05:06 AM                        I've never seen or used a Brenkert - I'm not sure that there even are any in Britain. But I'll take your word for it! Of the projectors that are commonly found in Britain and Europe my choice would be FP-20s for any booth which would regularly be showing older prints but not 70mm, but there may well be better options elsewhere. Agreed with Josh - 'Fox hole' sprocket teeth are a good way of preventing perf damage on older acetate elements (not just shrinkage, but severe deacetylation brittleness as well). The Vic 8s at one place I worked had them on permanently, and they didn't seem to cause any stability problems or perf damage to unshrunk prints with full-size perfs, either.  |  IP: Logged Josh Jones Redhat Posts: 1207 From: Plano, TX Registered: Apr 2000 posted 08-12-2004 05:08 PM                        Funny, that machine is 50 years old, yet it still puts out a better picture (stability wise) than most of the screens I have ever been in. JJ  |  IP: Logged

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