Mystery Anamorphic Cinemascope Lens - AVS Forum
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post #1 of 6 Old 05-31-2001, 11:26 AM - Thread Starter
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Hi,

I have the opportunity to buy an anamorphic lens used for projecting movies. The place selling it does not have much information on it. I was wondering if anyone in this forum may have an idea, or know where to look.

Here is what I know so far:

- It is a Bell & Howell Anamorphic Cinemascope lens.

- The side where the light goes in is about 70 mm. (The exit side is much larger, but I did not get a chance to measure it.)

- It is adjustable by turning the front half of the lens, and there are gradiations from 50 to 300. (Is this a focal length in feet? Or some other spec expressed in mm?)


I would like to use this on a project, which I will purchase soon. Thinking about the NEC LT-150, but want to see some of the newer DLPs with 6 section color wheels before I take the plunge.

Will this lens work? What would be the minimum focus distance that I can get? What is best way to examine it at the shop without taking it home (and paying for it)? They have a no refund policy.

Thanks in advance!
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post #2 of 6 Old 05-31-2001, 12:13 PM
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Don't pay more than $70 for this lens. It's an old CinemaScope lens meant for a large commercial theater. I have a couple that I got from eBay a while back. They do work and are generally of high quality, but there are some limitations that make them less than useful in home theater applications.

There are two problems that seem apparent from the description you have provided.

1) It's almost impossible to get a standard business projector to zoom small enough to fit the entire image through the lens. The result is that the corners are cut off or are much dimmer than the rest of the image. Some DLP projectors produce small enough beams at the primary lens so that this type of lens can be used, but most LCD and many DLP business projectors do not.

2) The focus adjustment doesn't allow for use in a normal sized home theater. 50-300 is the focus adjustment. 50 feet - 300 feet. Some other anamoprhic lenses will focus down to 15 feet or so, but it's a soft focus at that distance.

Overall, it may be worth playing with for ~$70, but don't purchase the lens with the expectation of using it within your eventual home theater.

Alan has been using a commercial ISCO short throw CinemaScope lens that was designed for the newer stadium seating type theaters that generally have shorter throw distances. He paid about $500 for this more modern lens/ Using this DLP projector he is able to just barely get the entire projected image through the lens. That particular lens works well in this particular case, but your mileage may and most likely will vary.
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post #3 of 6 Old 05-31-2001, 12:22 PM - Thread Starter
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Thanks a lot, this answers exactly what I wanted to know.

I guess old cinema projection lenses are all designed for 50 ft to 300 ft, and I probably will not find something used that can handle a shorter focal length. 15 ft is really the upper limit for me in terms of size, and a soft focus does not sound like a good thing. Also, I was just going to use it on a LT-150 (or equivalent), and it probably projects a large image because it is designed for presentations. Probably would not have fit.

And I was going to pay $200 for it..... Thanks!

---Ben

P.S. Yes, I saw Alan's thread, and that was when I started looking around for this.
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post #4 of 6 Old 05-31-2001, 12:33 PM
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Guys,
Don't forget that the cinemascope lenses overstretch the image with a 2x stretch instead of the necessary 1.76x horizontal stretch. This means you have to drop horizontal resolution (with PC software like YXY) to obtain the correct geometry. Also, vertical pixel gap can be an issue if you are using a (relatively) lower res SVGA (800x600) projector. Plus, there are vignetting issues (darkened out corners) if your projector's image isn't small enough. To correct that, you would need to buy a longer throw spherical lens, or scope lens with a wider entrance aperture. The Panamorph 2 makes more sense to me, unless you just want to fool around.
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post #5 of 6 Old 05-31-2001, 12:35 PM
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every few days I plug 'anamorphic prism' and 'anamorphic lens' through ebay in the hopes of either a cheap ISCO or turning up a super panatar or other Gottschalk Lens...

No luck on the prism front but there are regularly 35mm (70 mm +- input) anamorphics in the 25 - 50 $$ range... as mentioned above these have focal lengths 50 feet and up...

I have now missed 3 Super Panatars in the last month sold via web pages etc all for sub 100 dollars... At this price I would buy one to play with a variable rate device to look at its limitations v my much awaited Pannie...

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post #6 of 6 Old 05-31-2001, 12:42 PM - Thread Starter
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Thanks for all the responses. I guess $200 is way over the market price, especially for something just to fool around.

Has anyone tried a single lens that is flat on one side, and curved on the other (but only in one axis)? Would focusing be impossible on a setup like this? I am not very good with optics, that is why I am asking. It would seem to me that the curvature on the one side would determine the amount of stretching, etc. By finely tailoring that curvature (got no idea how to do that), it would seem possible. Perhaps getting a optometrist friend would be a good idea at this point.

---Ben
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