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» Film-Tech Forum ARCHIVE   » Operations   » Film Handlers' Forum   » What is a reverse anamorphic lens?

   
Author Topic: What is a reverse anamorphic lens?
Adam Martin
I'm not even gonna point out the irony.

Posts: 3686
From: Dallas, TX
Registered: Nov 2000


 - posted 10-18-2003 06:33 AM      Profile for Adam Martin   Author's Homepage   Email Adam Martin       Edit/Delete Post 
Someone in the Equipment Forum wants to buy a reverse anamorphic lens. Is this a lens that compresses the image? And what on earth would this be used for outside of camera or optical printing use?

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John Pytlak
Film God

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


 - posted 10-18-2003 06:44 AM      Profile for John Pytlak   Author's Homepage   Email John Pytlak   Send New Private Message       Edit/Delete Post 
In most cases, the 2X squeeze anamorphic lens used for "scope" projection MAGNIFIES the image by a factor of 2X horizontally. The focal length of the "prime" lens is chosen based on the HEIGHT of the image.

In long throw situations, an anamorphic lens may be oriented such that it REDUCES the magnification in the vertical direction by a factor of 1/2. The focal length of the "prime" lens would then be based on the WIDTH of the screen image desired. Reverse anamorphics are used when the throw is so long that there is no suitable long focal length prime lens available for the more commonly used 2X widthwise magnification.

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David Kilderry
Master Film Handler

Posts: 355
From: Melbourne Australia
Registered: Sep 1999


 - posted 10-18-2003 07:37 AM      Profile for David Kilderry   Author's Homepage   Email David Kilderry   Send New Private Message       Edit/Delete Post 
John is correct Adam. Here at the Lunar Drive-in Theatre we have throws up to 500 feet, finding the very tall focal length prime lenses for regular anamorphics is difficult hence us using reverse anamorphics on two of our screens. One is a Kollmorgen, popular brand from the 1960's era not often seen today, the other is a Kowa. Both let good light through to our big screens.

David Kilderry

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Robert Throop
Master Film Handler

Posts: 412
From: Vernon, NY USA
Registered: Jun 99


 - posted 10-18-2003 09:05 AM      Profile for Robert Throop   Email Robert Throop   Send New Private Message       Edit/Delete Post 
The first reverse anamorphs were made by B&L. Those had to be factory adjusted for throw AFAIK. The later Kollmorgan, Isco, Schneider lenses can be field adjusted just like any scope lens.

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Pete Lawrence
Expert Film Handler

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


 - posted 10-18-2003 09:33 AM      Profile for Pete Lawrence   Email Pete Lawrence   Send New Private Message       Edit/Delete Post 
In a pinch, a regular anamorphic lens can also simply be reversed end for end and used. Take a look at the Skyline Drive-in in the Pictures section. About half way down you'll see Ken Layton's smiling face holding what looks like a B&L 4" scope lens on the front of the projector. It's mounted backwards.

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Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000


 - posted 10-18-2003 12:33 PM      Profile for Paul G. Thompson   Email Paul G. Thompson   Send New Private Message       Edit/Delete Post 
I have two Kollmorgans. They are one big hunk of glass. Very heavy. They may need support to keep them from sagging when they are used.

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Adam Martin
I'm not even gonna point out the irony.

Posts: 3686
From: Dallas, TX
Registered: Nov 2000


 - posted 10-18-2003 04:17 PM      Profile for Adam Martin   Author's Homepage   Email Adam Martin       Edit/Delete Post 
Interesting ... the longest throw I've worked with was about 350 feet at a drive-in, where I was able to find "standard" lens configurations.

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Gordon McLeod
Film God

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


 - posted 10-18-2003 08:31 PM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
the problem was as the trow get to a certain length the focal length of the lens gets so long that they are inefficient even at 4" in diameter so the reverse anamoprhic drops the focal length back into the ball park of reasonably efficient lens design

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Barry Floyd
Phenomenal Film Handler

Posts: 1079
From: Lebanon, Tennessee, USA
Registered: Mar 2000


 - posted 10-19-2003 12:43 AM      Profile for Barry Floyd   Author's Homepage   Email Barry Floyd   Send New Private Message       Edit/Delete Post 
I'm using a brand new Schnieder(sp?) Reverse Anamorphic Scope at our drive-in. Kind of pricey.... but it puts a great picture on the screen.

Our screen is 25' x 60' with a 325' throw, and finding other lenses for that throw was almost impossible.

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Ron Keillor
Expert Film Handler

Posts: 166
From: Vancouver, B.C. Canada
Registered: Jul 2003


 - posted 10-19-2003 01:02 AM      Profile for Ron Keillor   Email Ron Keillor   Send New Private Message       Edit/Delete Post 
Back in my univerity days we screened 16mm. in an auditorium whose screen could not be widened. To use 'Scope pictures we squashed the picture down using an anamorphic adapter installed at 90° to keep the width constant. The old Bay and Colonial Theatres had to do that, their screen widths were fixed by proscenium arches. We referred to the process as "SquashoScope".

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