Film-Tech Forum ARCHIVE: Are there anamorphics that squeeze rather than stretch?

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Posted by George May (Member # 1060) on 04-02-2003, 03:34 AM:

All the anamorphics I have seen stretch the width of the picture leaving the height the same to get the required aspect ratio.

Are there any that squeeze the height instead? The reason I ask is that I have been asked to do a film at a venue with a lovely projection box (I run two side by side "portables"). Using a 120mm lens (the longest focal length I have) and with a flat negative I get just the picture width I want at the place the screen will be. But the client wants to mix flat and 'scope in their programme. I can't move the projectors to reduce the width before adding the anamorphic. What I need is to keep the width the same and reduce the height.

Any ideas? Do such lenses exist?

Thanks

George

Posted by Brad Miller (Member # 2) on 04-02-2003, 03:48 AM:

You need to get a different prime lens to use with your anamorphic. Tell us the distance to the screen and the width of your screen and it is easily calculated.

Posted by Lindsay Morris (Member # 1430) on 04-02-2003, 04:12 AM:

George,
Such lens did exist in the mid fifties and sixties when scope was in its early years but they were cheap and nasty. Lost a lot of light, gave vertical lines the bends and added a horrible brown cast to the screen image. Cannot remember the name of them but did use some at a cinema when the B&L anamorophics were taken up to do the job at the new owners drive in.

But what a lot of DI operators did later on when they were trying to get more screen light was to REVERSE the anamorphic in the holder so it squeeezed the height and changed the backing lens to a shorter focal length which was faster in terms of light loss than lens of 190mm or so which they otherwise used and it worked well.
I think there is still one country DI here in West Australia still using that setup.
To my mind I think if you just changed your aperture plate to scope and reversed the anamorphic it might just work OK with your W/S lens... nothing to lose... try it.
Lindsay

Posted by Darryl Spicer (Member # 711) on 04-02-2003, 08:37 AM:

I am a little confused about how you can take an anamorphic lens and make it squeeze an image that is already squeezed. All it can do is stretch the image. the only way it can squeeze is by sending informatiopn thru the anamorphic to a negative during photography and optical processing. You need to do as Brad stated in his post and everything will be fine.

Posted by John Pytlak (Member # 331) on 04-02-2003, 08:45 AM:

quote:
I am a little confused about how you can take an anamorphic lens and make it squeeze an image that is already squeezed.

As discussed, "reversing" an anamorphic would leave the width of the image as determined by the prime lens, but compress the height of the image on the film by a factor of 2.

Posted by Stephen Furley (Member # 1277) on 04-02-2003, 10:48 AM:

Hi George, are those the rather nice little Chineese made portables, where the take-up spoolbox door is hinged at the bottom, rather than the side. The photograph looks rather like one, but I'm not sure. If not, then I think the Chineese ones may be a copy of what you have.

Posted by Steve Guttag (Member # 268) on 04-02-2003, 11:32 AM:

Ya know both Schneider and ISCO still manufacture reverse anamorphics...not bad ones either...though a normal anamorphic is always preferred. Remember if your prime lens is over 140mm...your effective f-stop will be getting progressively larger than 2.0 and you will loose light.

Steve

Posted by Mark Gulbrandsen (Member # 72) on 04-02-2003, 04:30 PM:

I ahve typically gotten far more sharpness from the Schneider or ISCO reverse anamorphic that you get out of a standard 2X, but keep in mind that they are not meant for short throws.
Mark

Posted by Michael Brown (Member # 890) on 04-02-2003, 05:29 PM:

Am I being dumb? But all it seems is that George needs a
smaller sized Anamorphic lense.

One that will stretch the width out to the same width that the flat lense puts out.

All George wants to do is put out a scope image that has the same width as his flat image. The same that is done in cinemas that have top (or top and bottom) masking to change between flat and scope.

George, Give us some sizes.

Posted by Alan Gouger (Member # 543) on 04-03-2003, 10:54 AM:

George

There is such a lens from a few companies and they are very good quality. I have tried them.
While thier target market is for electronic display devises they also work perfect for film. They use a prisim design. The prismasonic is adjusyable so it will work with films aspect ratio verses videos. One is liquid filled an they also have a smaller solid model. They use very good coatings and contrast and light transmission are on par with isco. They also have plenty of apreture [Big Grin]

http://www.visr.com/
http://www.prismasonic.com/

[ 04-03-2003, 12:08 PM: Message edited by: Alan Gouger ]

Posted by Mark Gulbrandsen (Member # 72) on 04-04-2003, 06:02 AM:

Even with modern coatings that prismatic lens would have some inherent light loss. Looks no more to me than a copy of the original Panavision Panatar Anamorphic...... I also wonder how the focus is at short throws. The Panamorph lens says it has to be customized for long throws.... Interesting....
MArk @ CLACO

Posted by George May (Member # 1060) on 08-04-2003, 09:10 AM:

I return to this having not found a solution. A number of you, and other projectionists, have told me that simply inserting the anamorphic 'back to front' will do what I want. And indeed it does squueze the height except that I can't get the arrangement to focus. I've been told I should set the anamorphic range setting to the lens to screen distance _first_ and then focus the backing lens, but that doesn't seem to work either. I am experimenting with relatively short throws (down the drive at my house!). I don't have enough detailed optical knowledge to know what should happen. I am using French Chre'tien Hypergonar anamorphic lenses, which have throw markings on the barrel of 7-10-15-50-infinity (metres?) They are marked "Made in France" so perhaps it's feet after all. 50 metres is pretty close to infinity.

Can anyone help?

Thank you.

Posted by Barry Floyd (Member # 385) on 08-04-2003, 10:05 AM:

Reverse Anamorphic... that's what we're doing at our drive-in. Trying to find a lens that will produce a 25' x 58' picture from 325 feet away is a difficult, if not impossible task.

I've got a theatre tech in Pennsylvannia who is working on rounding up my lenses. So far, the best bet has been the use of the reverse anamorphic.

He said something about a "magnacon"(??) coupled with the flat lens. I'll have to see what he comes up with.