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TOPIC: screen ratios

screen ratios 28 Jun 2000 15:06 #505

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Another question for the forum.
To show other aspect ratio besides flat or scope for older classic films, silents or foreign films, do I need new lens or can I just get appeture flats for the other formats?
thanks
Don Shafer
Blackwell Theatre
Marietta, GA
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Re: screen ratios 29 Jun 2000 00:27 #506

  • RoxyVaudeville
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You can use your existing flat lense, however your picture will be smaller which will require moving in the masking if you don't want to see blank screen. And yes you will need to file new aperture plates to the proper aspect ratio if you want to show the entire picture properly.

It depends also on whether or not you can move your top masking up or not. If you have more height to your screen then what you use for scope, move the top masking up and you will get a larger picture in the old formats, and won't have to mask as much on the sides. If you have a lot of extra height, you may not need to mask in the sides at all. You will need new lenses so that you can fill the higher screen height. Depending on the amount of extra height, you may still have to mask in the sides and you will have to cut new aperture plates.

It will all depend on what aspect ratio the picture is in.

I keep four different sets of lenses on hand so that I can cover virtually whatever comes along.
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Re: screen ratios 18 Jul 2000 12:30 #507

  • John Pytlak
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You can calculate the correct focal length of lens needed for any particular format, throw, and screen size. Strong International has a "Lens Selector and Picture Size Computer" slide rule. IscoOptic and Schneider have on-line lens calculator programs:
http://www.schneideroptics.com/theatre/desprodn.html
http://www.iscooptic.de/english.html

For a "one-of" showing of a 1.37:1 "Academy Format" film, you can usually use the same prime lens used for scope, but without the anamorphic attachment. With the correct 0.825 x 0.602 inch aperture, the image on the screen will not fill the screen height, but will be the correct composition (bring in the masking as needed).

If you own an art or repretory theatre, you really should have the lenses, apertures and masking for all the important formats:
2.39:1 scope, 1.85:1, 1.66:1, 1.37:1, Silent.
If you show silent films, consider a projector that can run 16 frames per second, and a 3-blade shutter.

John P. Pytlak
EI Worldwide Technical Services
Eastman Kodak Company RL/69
Rochester, NY 14650-1922
Telephone: 716-477-5325
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John P. Pytlak, Senior Technical Specialist
Customer Technical Services
Entertainment Imaging
Research Labs, Building 69, Room 7525A
Eastman Kodak Company
Rochester, NY 14650-1922
Telephone: +1 585-477-5325 Fax: +1 585-722-7243
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Website: http://www.kodak.com/go/motion
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