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Topic: focus problem due to heat?
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Paul G. Thompson
The Weenie Man
Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000
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posted 05-04-2002 01:33 AM
Check your xenon lamp focus. Check your coolant temperature about 1/2 an hour or so before the problem starts, and check the temperature after the problem starts. If you are using a coolant circulator, a cheap thermometer dunked in the coolant will work, or just take a thermometer and duct tape the thermometer bulb to the coolant return line. That should give an idea or two. I would suspect you could also have a lens problem. If the lens size of the other side is the same as the problem side, swap the lens and see if the problem follows it. But the big thing is check your lamp focus first.
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Jerry Chase
Phenomenal Film Handler
Posts: 1068
From: Margate, FL, USA
Registered: Nov 2000
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posted 05-04-2002 08:41 PM
Swap prints. See if the focus problem follows the print or projector. Possibilities:
Is the prime lens the same for both scope and flat? If so, is it shifting focus with heat? I could be off track here, but is the print on the platter wrapping a little loose on the outside? Heat could be warping the print, but the torque and pressure on the front end of the platter wrap might be mitigating the problem on the first reels. On some platters outer layers don't get "ironed" as much as the inner layers.
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John Pytlak
Film God
Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000
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posted 05-06-2002 11:01 AM
Usually a "silver retention" print process is used for an entire movie, but might it have been used here for just a reel or two?:
http://www.kodak.com/country/US/en/motion/support/processing/skip.shtml If silver is deliberately left in the print to achieve a certain "look", it will absorb more radiant energy and be more sensitive to heat-related problems. With a 6K lamp, you MUST pay attention to proper lamp alignment, heat filtration, and water cooling:
http://www.kodak.com/country/US/en/motion/newsletters/reel/fall97/pytlak.shtml
http://www.kodak.com/country/US/en/motion/newsletters/reel/winter97/projection.shtml ------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
e-mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion
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