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Author Topic: Focusing Problems Eric Koppen Film Handler Posts: 1 From: Sandwich, Illinois, United States Registered: Feb 2004 posted 11-06-2004 08:20 PM                     Hello, I am having a focusing problem, and I was hoping you folks could help. I work in a 7 screen theatre, and we run Christie projectors. The problem began at the same time throughout about 4-5 theatres, and in formats Flat and Scope between the theatres. The problem that is happening is that when we go to start the film, it is out of focus. So we adjust it to be in focus, and by the time it gets to the Feature it is out of focus and requires to be focused again. I believe it is a heat issue, where it goes out of focus when the lens cools inbetween sets, so its focused, then it goes out of focus again when the lens heats up again. Can someone help me out? If you need more specific info, let me know. Thank you. Eric  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 11-06-2004 09:56 PM                     has your lamps been changed or refocused and the problem developed or is your exhaust fan working  |  IP: Logged Ian Joseph Parfrey Film Handler Posts: 56 From: Bollier Queensland Australia Registered: Sep 2004 posted 11-07-2004 01:56 AM                     Any emulsion piling up on gate bands?  |  IP: Logged Ferdinando Innocenti Film Handler Posts: 79 From: Genova / Italy Registered: Jun 2004 posted 11-07-2004 02:26 AM                     How old is the cinema? Is it the first time it happens? If so, are there any changes in lamps (which brand?) and lamphouse? Have you some kind of electrical motor for focusing (I had a problem once with a switch of a motor)? Besides, check the temperature of the film. If you need to readjust focus many times, also during the feature, it could be a film deformation, so check every cooling device you had. Ciao Nando  |  IP: Logged Adam Martin I'm not even gonna point out the irony. Posts: 3686 From: Dallas, TX Registered: Nov 2000 posted 11-07-2004 01:46 PM                     I also vote for checking the exhaust fan, maybe a loose or broken belt.  |  IP: Logged Ian Joseph Parfrey Film Handler Posts: 56 From: Bollier Queensland Australia Registered: Sep 2004 posted 11-07-2004 03:29 PM                     Or an incorrectly clamped lens.  |  IP: Logged Adam Martin I'm not even gonna point out the irony. Posts: 3686 From: Dallas, TX Registered: Nov 2000 posted 11-07-2004 04:28 PM                     In 4-5 auditoriums all at the same time?  |  IP: Logged Will Kutler Phenomenal Film Handler Posts: 1506 From: Tucson, AZ, USA Registered: Feb 2001 posted 11-07-2004 04:42 PM                     Also check your lenses. If you remove the lenses and gently shake them, do you hear the elements rattling around? The multi-plex where I worked had all brand new Schneider lenses that apparently came from a bad batch. This problem occured on most of the lenses, and all at the same time. Just about all our lenses had to be sent in for servicing.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 11-07-2004 08:51 PM                        quote: Eric Koppen The problem began at the same time throughout about 4-5 theatres, and in formats Flat and Scope between the theatres. The problem that is happening is that when we go to start the film, it is out of focus. So we adjust it to be in focus, and by the time it gets to the Feature it is out of focus and requires to be focused again. It could be that your pre-show rolling stock ads and trailers have so much "core-set" that they focus differently than the feature. Did you change the way you handle trailers (e.g., winding orientation?). Try winding on larger cores or with a different orientation to "relax" the core-set clockspringing. Might you be focusing on a snipe that has been treated with a UV-cured protective coating (e.g., PhotoGard)? They may focus differently.  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 11-07-2004 11:30 PM                     My question is: Does the projector go out of focus gradually or suddenly? If it happens suddenly, I vote for John P's theory. Different pieces of film can focus differently. Verify this by standing by the projector and watching the focus. It might seem to suddenly go out of focus. If it happens gradually, I vote for Will's theory. The lens(es) could be heating up and expanding, thus throwing the picture out of focus. When the lens cools, it goes back to normal. Have you changed the xenon lamp(s) recently? If so, I vote with Gordon and Adam. Check the alignment/focus of the xenon lamp. It could be out of whack and causing parts of the projector to heat up unevenly. As with the above theory, "heat = expansion = out of focus." While you're in there, check your cooling & exhaust fans and/or your water circulators to see if they are all working OK. Just out of curiosity: Do you have Christie lamphouses/consoles with an "Auto Focus" button on them? I've seen more than a few people who change a lamp and think that the "Auto Focus" button automatically aligns the lamp after you change it. In reality, it only moves the lamp's "beamspread" adjustment back and forth when you switch between FLAT and SCOPE films. It has to be recalibrated every time you change a lamp. (Or at least check the calibration.) If this adjustment isn't made or if it's done wrong, it can cause hot spotting which MIGHT cause symptoms you describe. It can also burn your film! Thus, if you have changed lamps recently, this would be a VERY good thing to check into.  |  IP: Logged

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