Film-Tech Forum ARCHIVE: Extending the focus range of anamorphics

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Topic: Extending the focus range of anamorphics

Pete Lawrence
Expert Film Handler

Posts: 192
From: Middleburg, PA
Registered: Aug 1999

posted 09-21-1999 08:31 PM

Hi all. I have a problem I need some advice on. I have a very small screening room set up at home in the basement, strictly as a hobby. Projectors are old Navy DeVry XD portable machines. Nice machines when given a little TLC. The projector to screen distance is only 19 feet. A 3 inch f.l. lens produces a nice sharp flat image. Now here is the problem, the throw is to short to properly focus the standard Bausch and Lomb red ring anamorphic lenses I have. Is there any way to squeeze a little more adjustment range (on the short side) out of the scope lenses? At about 30 feet they focus fine. I just don't have that much space.

On a similar subject, what are the rules for choosing extension rings for scope lenses? The two I know of are as follows. Use enough extension so the scope attachment is moved out in front of anything sticking out of the of the projector, such as the focus knob. Keep the extension short enough so you don't cut off the corners of the light cone coming out of the primary lens. Is there any position between these two extremes that's optimum?

Thanks,
Pete

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 09-22-1999 04:54 AM

I think you're going to have to trade up for some newer anamorphics. I'm unaware of any modifications, but if someout out there knows something I'd love to know about it.

As to the second part of your post, the less distance between the prime lens and anamorphic the better.

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Gordon McLeod
Film God

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

posted 09-23-1999 11:39 AM

The old vidoscope will focus usually down to around 20 feet

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Stefan Scholz
Expert Film Handler

Posts: 223
From: Schoenberg, Germany
Registered: Sep 1999

posted 09-24-1999 02:06 PM

The recent ISCO and Shneider combined type (baselens/anamorphoser combi) could be focused down to 5 ft. But they are rather costly, you may be lucky to find a used or "superflous" one at larger theatres.

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Pete Lawrence
Expert Film Handler

Posts: 192
From: Middleburg, PA
Registered: Aug 1999

posted 09-29-1999 01:09 AM

Thanks Guys,

I kind of thought the answer would be "no" or "it's time for a lens upgrade". Unfortunately, the budget (this is only a hobby) doesn't allow for a $4000 ISCO and Shneider lens upgrade. I do have a mint matched pair of Vidoscope anamorphics but they focus only slightly shorter than the B&L lenses. Both are off the bottom of the scale. Close but not quite right.

I guess it's time to move the wall back ten feet. That's the option that's within the budget!

Thanks for the advice.
Pete

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Gordon McLeod
Film God

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

posted 09-30-1999 01:28 PM

I had no problem getting my vidoscopes to focus to 18 feet in my screening room. You have to keep loosening the black locking ring as you tighten the barrel in

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