This is topic Extending the focus range of anamorphics in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Pete Lawrence (Member # 130) on 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
Posted by Brad Miller (Member # 2) on 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.
Posted by Gordon McLeod (Member # 33) on 09-23-1999, 11:39 AM:
The old vidoscope will focus usually down to around 20 feet
Posted by Stefan Scholz (Member # 147) on 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.
Posted by Pete Lawrence (Member # 130) on 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
Posted by Gordon McLeod (Member # 33) on 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