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Topic: Broken Lens

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 01-14-2002 09:20 AM

Proper lamp alignment is critical. Also, with a 5K lamp, I hope you are using a heat filter on your lamphouse!

Steve

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"Old projectionists never die, they just changeover!"

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 01-14-2002 12:12 PM

The way I feel about it, I'd rather have the lamp focused so that it's too dim than too hot. You can always "bump it up" if you need to but if the lamp is too hot you can do damage before you even have a chance to correct the problem.

How I would do it is to take the lens out and focus it the way it should be, but then back off just a hair bit. Then I'd cut the black credits off an old trailer or something, make a loop out of it and run that for a while. During that time I'd check it every few minutes. If the lens and/or gate is getting too hot I'd back off a bit more. Also remember that the black film will start to get hot after a few loops through the projector. If the black film can take repeated loops without burning or buckling it ought to be good enough for a "go show". Let it run for a few more minutes and check it again. I'd repeat the check/adjust procedure until I was comfortable with it.

Whenever I focus a lamphouse (putting in a new lamp or making repairs) I always baby sit it for the first show to make sure nothing bad is happening. Every time I have had film burned or had lens damaged from heat it was because somebody did an adjustment and didn't do any testing or checking before they started a "go show".

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 01-16-2002 09:12 AM

Here are links to some articles on heat damage:
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
http://www.kodak.com/country/US/en/motion/screencheck/evaluation.shtml
http://www.kodak.com/country/US/en/motion/newsletters/reel/spring98/pointers.shtml

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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

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Ben Stephenson
Film Handler

Posts: 29
From: Manchester, England
Registered: Jan 2001

posted 01-22-2002 05:48 PM

At the moment i have a cracked scope lense in the bigest 35mm screen in Europe and it still looks ok but when the lense was fine in still was imposable to focus !

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 01-22-2002 09:34 PM

Ben said: "At the moment i have a cracked scope lense in the bigest 35mm screen in Europe and it still looks ok but when the lense was fine in still was imposable to focus !"

Even if the crack is on a lens element that isn't imaged, it's very likely that it is a "contrast killer":
http://www.kodak.com/country/US/en/motion/newsletters/reel/december99/pytlak.shtml

As far as focusing difficulty, does your prime lens have a really short focal length? Or is there some problem with the anamorphic attachment?

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Ben Stephenson
Film Handler

Posts: 29
From: Manchester, England
Registered: Jan 2001

posted 01-23-2002 12:59 PM

prime lens has a really short focal length and the anamorphic attachment is fine, just ordered and new lense after i just got the wrong replacment !

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