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Topic: Uncrisp image

Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 01-17-2005 08:38 PM

Since you say they are idendical twins swap the lens and see if the problem follows them

Lamphouse alignment can make terrific focus issues

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Richard Hamilton
Phenomenal Film Handler

Posts: 1341
From: Evansville, Indiana
Registered: Jan 2000

posted 01-17-2005 10:24 PM

If you said that you changed lenses, prints and port hole glass, what is left? I agree with Gord. I would first check working distances. Then lamphouse alignment. Then check the light readings on each screen. If all is equal, then they should be the same. I would compare the image looking at RP-40, not changing the prints, and using the same lens.

If it is still bad, I would have to ask someone with more knowledge (than me), could one screen be a higher gain and the light levels have an affect? Maybe the good screen is a higher gain or silver screen and the bad one has a matte finish. If you are trying to match the light levels, then you could create a hot spot on the matte screen causing the film to heat up and distort in the gate?

Rick

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Peter Mork
Expert Film Handler

Posts: 181
From: Newton, MA, USA
Registered: Jun 2002

posted 01-17-2005 11:18 PM

quote: Wolff King Morrow
Is there any way you could remove your port glass just to make sure its not an impurity in the glass?

Tried it. It didn't help.

quote: Richard Hamilton was the last to post

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Peter Mork
Expert Film Handler

Posts: 181
From: Newton, MA, USA
Registered: Jun 2002

posted 01-17-2005 11:22 PM

quote: Wolff King Morrow
Is there any way you could remove your port glass just to make sure its not an impurity in the glass?

Tried it. It didn't help.

quote: John Pytlak
Or you might be able to see a reflection of a light or shiny surface behind the screen through the perfs.

I didn't think of that. I think the screens have similar black baffling behind them, but will check.

quote: Leo Enticknap
I know it's a bit of a faff removing the lamps, replacing them and refocusing the mirrors; but swapping the mirrors would either identify or rule that out as the cause of the problem, once and for all.

Also, do you have any heat filter glass in the lamphouses?

Yes, both have filter glass. I will try swapping the mirrors when I get a chance if nothing else works.

quote: Richard Hamilton
could one screen be a higher gain and the light levels have an affect?

The two screens are the same age and material, and are fairly clean.

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Richard Hamilton
Phenomenal Film Handler

Posts: 1341
From: Evansville, Indiana
Registered: Jan 2000

posted 01-18-2005 12:54 AM

Peter,
Can you just remove the heat filter from the screen in question? I don't think that a 2000w bulb will damage the film if properly aligned. this would rule out the heat filter right away. Are the lenses integrated? If not, how does the prime lens look on screen if you take the anamorphic off?

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Peter Mork
Expert Film Handler

Posts: 181
From: Newton, MA, USA
Registered: Jun 2002

posted 01-18-2005 01:21 AM

Removing heat filter, another good thing to try. I'll do it this weekend.

Lens isn't integrated, so I can try the prime by itself. As I said, subjectively speaking the problem seems greater when projecting scope.

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Leo Enticknap
Film God

Posts: 7474
From: Loma Linda, CA
Registered: Jul 2000

posted 01-18-2005 01:53 AM

That would seem to point to the anamorph, but as Richard points out a print can look a bit confusing - an RP40 should show any difference clearly.

Sorry - should have been a bit more explicit viz heat filter panes. I meant that before going to the hassle of swapping the mirrors it might be an idea to check those out (e.g. swap them or look for any slight difference in the mounting angle between the two).

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Monte L Fullmer
Film God

Posts: 8367
From: Nampa, Idaho, USA
Registered: Nov 2004

posted 01-19-2005 12:39 AM

..okey, even though I made mention of this is a while back with this topic of a sharp image, here is a couple of pics of a good warped mirror toasted to oblivion - Monte

Goes to show you that unexperienced operations can exist. Light was so bad from this mirror it was a necessity for a mirror replacment.

-thx Monte

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Peter Mork
Expert Film Handler

Posts: 181
From: Newton, MA, USA
Registered: Jun 2002

posted 01-19-2005 08:29 AM

Oh boy. Well, I'm sure mine's not toasted like that.

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Matt Zeiner
Expert Film Handler

Posts: 146
From: Windsor, CT USA
Registered: Sep 2003

posted 01-22-2005 10:02 AM

Deifinitely check the heat filter - Had one yesterday that was causing a 35+% reduction in light output and very poor contrast In a Big Sky lamp. It was driving me nuts for quite a while - checked and tweaked the alignment repeatedly, still couldn't get more than 12 fl in scope with a 3k lamp and 25 foot screen. Removed the heat filter and poof! 20 fl in the center and contrast was sharp as a tack. had to back off the current a bit.

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John Pytlak
Film God

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

posted 01-22-2005 11:05 AM

You may regret removing that heat filter if you ever play a B&W print or a color print processed with a "silver retention" process. [Eek!]

Any silver in the image absorbs much more infrared energy than a dye only print.

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Leo Enticknap
Film God

Posts: 7474
From: Loma Linda, CA
Registered: Jul 2000

posted 01-22-2005 12:36 PM

Given that both of these projectors have heat filters and only one is causing an uncrisp image, it doesn't look like the existence of a heat filter per se is the problem (unless there is any other variable between the two screens which is causing the problem in combination with the filter and which we don't know about). Agreed entirely with John - I'd be reluctant to remove it altogether, and also because the extra light might make it difficult to see if the uncrispness is still there. But swapping the filter panes between the two projectors would tell you if one of them is NFG.

I'm starting to get a gut feeling that either the heat filter or the mirror is the culprit, simply because everything else seems to have have been ruled out. Sod's law strikes again, because if it comes down to the mirror, it's a much bigger job swapping them than anything else.

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Matt Zeiner
Expert Film Handler

Posts: 146
From: Windsor, CT USA
Registered: Sep 2003

posted 01-22-2005 12:45 PM

Well sure. I believe the filter on this particular lamp was rated for 7% reduction in visible light (optiforms makes it.) Coating was burnt a bit. We installed the heat filters in the first place precisely because they are an art house and do run B&W films quite often. We will be getting a replacement.

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