my profile | my password | search | faq & rules | forum home

» Film-Tech Forum ARCHIVE   » Operations   » Film Handlers' Forum   » Drifting Focus

Author Topic: Drifting Focus Patrick Matthews Film Handler Posts: 86 From: Kansas City, MO, USA Registered: Sep 2004 posted 10-17-2005 02:59 PM                     Hi all, out projector (PRO 35) has been drifting focus recently. It is just the second projector (we have two for changeovers) and I just can't seem to get the whole picture in focus. This happens on scope and flat film. There is nothing on any of the runners or in the gate that is obstructing the film and I just can figure it out. Any ideas?  |  IP: Logged Jeff Taylor Jedi Master Film Handler Posts: 601 From: Chatham, NJ/East Hampton, NY Registered: Apr 2000 posted 10-17-2005 03:06 PM                     Is the whole picture drifting out or in and out of focus uniformly, or are you having problems pulling an even focus i.e. center to edges or left to right?  |  IP: Logged Patrick Matthews Film Handler Posts: 86 From: Kansas City, MO, USA Registered: Sep 2004 posted 10-17-2005 03:13 PM                     I'm having trouble getting a uniform focus. Either the center of the screen will be in focus but not the edges or visa versa.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 10-17-2005 04:22 PM                     Check both lenses to see if the elements inside are loose. Age can cause the lock rings to come unscrewed abit to make the elements not be tight within the element barrel. Tap the barrel and see if the elements rattle within. Elements loose will have problems of maintaining proper focus. You also could have some burnt lenses. Anyone left the dowser open and left the lamp on (which is lethal to lenses with naked light cooking up things inside)? With scope, wonder if the fine focusing ring has been altered some to cause improper focus with the anamorphic attachment(s). -Monte  |  IP: Logged Marin Zorica Jedi Master Film Handler Posts: 671 From: Biograd na Moru, Croatia Registered: May 2003 posted 10-17-2005 04:31 PM                     Also you must check you film gate! May bee tension is too high and film runs squized so distance from every part of film in frame to lenses is not same. Or film gate isn't positioned in parallel with lens holder,and then off course with lenses.  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 10-17-2005 05:30 PM                        What kind of gate does the Pro35 have? Is it like a modern Simplex/Century SA gate (curved with tension bands), an older-style Simplex/Century C or H gate (straight or curved, but without bands, and with two tension adjustment knobs), or something totally different? What size lamp and what type of lenses (focal length and f/stop)? What happens if you interchange the gates and traps between machines (if that's even possible; I'm not familiar with the Pro35)?  |  IP: Logged Patrick Matthews Film Handler Posts: 86 From: Kansas City, MO, USA Registered: Sep 2004 posted 10-17-2005 05:52 PM                     It is the older style with straight and the two tension knobs. We have a 2k lamp and our throw is 48 feet.  |  IP: Logged Dan Lyons Jedi Master Film Handler Posts: 698 From: Seal Beach, CA Registered: Sep 2002 posted 10-17-2005 06:00 PM                     turret or single lens model?  |  IP: Logged Patrick Matthews Film Handler Posts: 86 From: Kansas City, MO, USA Registered: Sep 2004 posted 10-17-2005 06:11 PM                     Single Lens  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 10-17-2005 06:50 PM                     PRO35 units from Ballantyne are one of the most unique, yet aggravating machines ever built. The plus being that the whole transmission is fully encased in an submerged oil bath with an oil fill on the outside of the case with an oil level marking. Then, the other end of the belt pulley shaft is the cam for the intermittent (and a pretty good sized intermittent assembly as well)And ... there's that damned coupling device to frame with since the intermittent assembly doesn't roll on its axis as does the Simplex, or move up and down as with the Century and Christie. But the intermittent shaft is split in two-one end with the starwheel and the other end holding the sprocket, with spiral grooving at each end of each shaft with a nylon coupler that slides back and forth between the spirals to "rotate" the intermittent sprocket for framing....) This was made so that the shutter didn't have to compensate for the attack (first sprocket hole) position of the intermittent sprocket. Dowser is a central hinged plate on the shutter shaft with a goofy type of spring selinoid to pull that thick plate of aluminum up. PRO35's looked like it borrowed some parts from the Simplex, mainly pad roller assemblies, gate and trap parts (all flate gate variety) and shoes of sorts. PRO's were mainly single lens models, with the exception of the MARK-VII that had the sliding lens bracket to hold both lenses-and the flat lens was a Magnacom lens since both lenses used one common base lens mounted in the lens frame. If you know how to thread a PRO just right, they can be a very quiet machine. But if the loop sizes are a bit too small, or a bit too big, then these PROS can sound like thrashing machines beating themselves to death. "Mr.Scott", if you want to "bone" up on a PRO-35, head to the manual section, open up the PDF on a PRO-35 manual and do some studying on these beasts. Here is some very good reading in store for you. -Monte  |  IP: Logged Darryl Spicer Film God Posts: 3250 From: Lexington, KY, USA Registered: Dec 2000 posted 10-17-2005 07:56 PM                    check the latteral guide on the gate trap for dirt accumulation around the spring and against the guide. There should be movment in the guide. Just remove the screw and the square guide and clean it off and rotate it from what it was because there probably is a groove in it too. Make sure to clean out around the area the guide goes in. I used to run pro 35's for about 8 years. Other than keystoning and or lens issues I have found the guide to cause focus issues as described if it does not move out enough to allow the film not to bow in the gate.  |  IP: Logged John McConnel Expert Film Handler Posts: 118 From: Okmulgee, OK USA Registered: Nov 2003 posted 10-17-2005 08:02 PM                        Have you exchanged lenses between projectors, to confirm that it's not a lens problem?  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 10-17-2005 08:08 PM                        Interestingly, the pro-35 is an Americanized FP-35. (Ballantyne was once the Norelco (Kinoton) distributor for North America......until they copied the machine.) Louis  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 10-17-2005 08:26 PM                     Actually they were assembling the FP20 (building the lamphouse table and column) as well as casting some of the bases for the DP70 In this case I suspect that the rails are causing the film to cup away from the lens (also a lamp that has a hot spot will make it worse) There is a spring loaded presure pad at the top of the trap that could be the culprit also the rails can be moved in and out and they may have shifted (an alignment tool is required) Also even though the gate lookes straight some of them had a radial curve  |  IP: Logged

All times are Central (GMT -6:00)

Printer-friendly view of this topic

Hop To: Select a Forum: Category: Operations -------------------- Digital Cinema Forum Film Handlers' Forum Large Format Forum Ground Level Feature Info, Trailer Attachments & REAL Credit Offsets Category: Community -------------------- Film-Yak Film Handlers' Movie Reviews The Afterlife Bob Maar's Joke-A-Thon Category: Classified -------------------- Equipment and Supplies Wanted/For Sale Help Wanted/Seeking Employment Category: System -------------------- Software Beta Testing Forum

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.