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What about using our anamorphic lenses in the vertical position so that they stretch 4:3 films to fill the entire 1920 raster? I did the math just now, and the optical stretch used to get 2.35 out of 16:9 (1.32x) is pretty much the same we'd need vertically to get a 4:3 image out of a 16:9 image. There's a difference, but it seems close enough.
It;s not "close enough" it's exact... as long as your system has a way of expanding by one-third, instead of vertically stretching by one third. Of course a pre-expanded anamorphic version of the movie (the subject of this thread) would help. Otherwise you need to have the feature available on your projector. Not all have it.
Re. "Close enough": You're probably getting slightly confused by using "2.35:1" as your widescreen bench mark. A 16:9 screen expanded is actually 2.37:1.
How to...
1. You expand a 4:3 movie by one third (or get a pre-expanded version from Folded Space). Everyone on-screen suddenly gets short and fat (art echoing life here, I think).
2. Rotate your anamorphic lens by 90 degrees (probably not a good idea for square prism systems - and some cylindricals - that don't rotate)
3. Your image will now be in 4:3 aspect, but larger, so you have to re-align your anamorphic, zoom your projector smaller (to 3/4 height), re-offset and re-focus it too (At last! A use for those "zoom memory" functions!")
You actually end up with a slightly brighter picture.
Here's why...
The reduction in size from having to zoom smaller increases the brightness by a theoretical 16/9 (1.78 times) - the inverse of 3/4-squared.
You then lose a few percent due to the reduced aperture (increased
f-number) that zooming smaller causes, plus about 38% from the anamorphic lens (33% plus a few percent for transmission loss).
Say, 50% in all of your new brightness due to the smaller image is lost.
But you have an extra 78% to play with, so nett gain is around 25% to 30% in brightness over a same sized non-anamorphic image. Anamorphic finally makes something BRIGHTER!
There's some fiddling involved, but it does work OK. However, it's NOT something you'd do routinely. Best to save up a whole bunch of 4:3 movies for a marathon to make the best of the altered settings.