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Author Topic: Bad Focus John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 07-06-2004 01:44 PM                        Barry: Sounds like you may have gotten into an issue of excessive radiant energy causing "focus flutter". Perhaps you are "hot spotting" your lamp more to get more light in the center of the screen, or your heat filtration has become less effective with age. Titles against a dark background are often the most critical scene for this issue. Here are some articles that I wrote: http://www.kodak.com/US/en/motion/newsletters/pytlak/fall97.shtml http://www.kodak.com/US/en/motion/newsletters/pytlak/winter97.shtml Gate tension can sometimes help. Another issue that can make "focus flutter" worse is high humidity or dampness. As the excess moisture in the gelatin film emulsion is driven off by the heat of the lamp, the film changes shape in the gate. Keep your projection room between 50 and 60 percent RH (use air conditioning or a dehumidifier in really humid weather). I know it's tough to do in a drive-in, but try your best to keep the booth humidity in control.  |  IP: Logged Ferdinando Innocenti Film Handler Posts: 79 From: Genova / Italy Registered: Jun 2004 posted 07-06-2004 05:17 PM                     If it’s impossible to have a good focus on the center (out of focus at the sides) the problem is not in projector position, but in the lens. It’s important to know how is the focus with the 115 prime. I think you tried to adjust the anamorphic lens; hadn’t it any improvements? Ciao Nando  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 07-06-2004 05:48 PM                     "My tech (who showed up as a customer on Saturday night) seemed to think that either the projector was not lined up 90 degrees perpendicular to the screen or that something is wrong with the lens. He ran a loop of test film on Saturday night right before the show, and made what adjustments he could. It's still not right. I didn't have this problem last year...." Well your tech is wrong as you said the problem wasn't there last year so that rules out postion alignment unless you moved the machine My bets are on focus flutter due to heat did you put in a new lamp this season try defocusing it a bit and see if it helps  |  IP: Logged Barry Floyd Phenomenal Film Handler Posts: 1079 From: Lebanon, Tennessee, USA Registered: Mar 2000 posted 07-07-2004 10:25 AM                        Our tech "DID" re-focus the lamphouse right at the beginning of the season. We had a "hot-spot" on the lower right side of the screen, and he moved the bulb around in the yoke until the screen was evenly illuminated. Our lamphouse is a Xenex II, running an Osram 4kw lamp. No "heat-filters" or anything that I can see. I'll take a photo with the digital camera and post it if you guys think it would help.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 07-07-2004 12:16 PM                        Any chance your lamp alignment and focus got knocked out of position? Your "heat filter" is a "cold coated" dichroic coating on the lamphouse metal reflector. Be sure your lamphouse is well ventilated to keep the metal reflector cool and maintain efficiency in eliminating excess heat. http://www.kneisley.com/LampH2.htm quote: Kneisley Xenex II Lamphouse Has newest 12.5 inch metal reflector (computer optimized design), cold coated. Heat filter not required.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 07-07-2004 01:33 PM                     lamp and lamphouse alignment effect lens focus as they are all part of the same optical system they are very interelated  |  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 07-07-2004 10:40 PM                        Have you tried running any NEW scope trailers (or anything else... even NEW flat trailers run in scope) since you had the lamp re-focused? It might be possible that you burnt your print.  |  IP: Logged Jack Ondracek Film God Posts: 2348 From: Port Orchard, WA, USA Registered: Oct 2002 posted 07-07-2004 11:12 PM                        While interrelated, I doubt that lamphouse alignment would make such a difference that his center credits would be unreadable. Barry... just to toss a hat in the ring... have you cleaned your lenses recently... as in, have you unscrewed your prime lens and used any cleaner on it? I'm wondering if you didn't seal in some of the cleaner before it evaporated. That can put a fog spot in there that will play hell with your focus. The film probably isn't getting pinched, since you've got a Simplex... and the flat image looks fine.  |  IP: Logged System Notices Forum Watchdog / Soup Nazi Posts: 215 Registered: Apr 2004 posted 07-17-2007 11:12 AM                 It has been 1104 days since the last post.  |  IP: Logged Barry Floyd Phenomenal Film Handler Posts: 1079 From: Lebanon, Tennessee, USA Registered: Mar 2000 posted 07-17-2007 11:12 AM                        Three years later, and I'm bumping this one up again. Same theatre (drive-in), new screen (actually 2 years old now), but we're having some scope focus issues again. Lenses: Schnieder 115mm prime + ISCO 1/2 Reverse Anamorphic Adaptor. (Both lenses were purchased used in August 2005) Screen: 25' x 60' Throw: 350'-0" (Drive-In) We have a spot in the bottom center of our scope image that stays out of focus. If I adjust the focus knob to bring it in focus, the rest of the pictures goes out of focus. Last night I actually pulled the lens out of the mount and flipped it 180 degrees, and even with the lens upside-down, it was still out of focus. I was hoping that by flipping the lens I could eliminate any loose element scenerios. Any ideas? Is it possible that when we tore the machine down several years ago and removed the lensmount, that it wasn't put back in exactly square to the film plane? I have another projector head I can swap out to see if it makes a difference.  |  IP: Logged Darryl Spicer Film God Posts: 3250 From: Lexington, KY, USA Registered: Dec 2000 posted 07-17-2007 12:49 PM                    Have you tried running the RP-40 test film after close when it is completly dark outside and check the focus on the anamorphic. Is the anamorphic maxed out for distance? Had this anamorphic been focusing fine before?  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 07-17-2007 01:30 PM                        REmove the anamorphic and look at the target film with only the back up lens. This will confirm or deny the anamorphic. Louis  |  IP: Logged Barry Floyd Phenomenal Film Handler Posts: 1079 From: Lebanon, Tennessee, USA Registered: Mar 2000 posted 07-23-2007 10:00 AM                        I've found a temporary solution to my Scope focus problem. Like someone suggested to me last week, I took the lens and rotated it 180 degrees in the lens barrel of the projector and the focus problem went away. That being the case, would that suggest that one of the elements on the lens has shifted?  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 07-23-2007 10:46 AM                     If its a Schnelder or ISCO lens its far more likely that the back up lens has a loose element or the whole back up lens is just plain loose from the anamorphic itself. Rotating the scope lens itself may have allowed it to fall back into place... at least for now. If this is the case it will fall out again at some point. Mark  |  IP: Logged

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