Lenses for vertically stretching 16:9 to 4:3?

No, it's not a stupid question.


Whether you use an expansion or (rare nowadays) a vertical compression lens, all you need to do is rotate the lens 90 degrees to the side and zoom your projector to get the image to fit the screen.

Expansion Lens:

Rotating the lens 90 degrees will stretch the vertical by 1.33x, making the "9" in 16:9 now 12.


16:12 = 4:3... got it?

Note: picture - although in the correct aspect ratio - will be too high, need to zoom projector smaller to fit screen.


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Compression Lens:

Rotating a compression lens 90 degrees sideways will make the "16" in 16:9 "12", leaving you with a ... boom-tish!


12:9 = 4:3 aspect ratio.

Note: no zooming required when using a Vertical Compression lens, as you are only compressing width, therefore height does not change.


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Does it work? Sure does. I do it myself a lot when we're having a B&W Classic Movie Night. The picture is amazingly bright, as you are fitting more light (from the full panel) into a smaller space, instead of the other way around.



Quote:
So I'd just need an anamorphic lens that can be rotated 90 degrees, then.

Click to expand...

Yep.


Another thing that occurred to me is that if you use a standard horizontal expansion lens and are therefore zooming the projecter a bit smaller (to shrink the stretched vertical back to a fixed screen height), this would give you more glass to work with, or rather the same amount of glass with a smaller back-end image impinging upon it.


Rotating a Vertical Compression lens would give you less glass to work with if you were utilising a rectangular rear lens device like any of the prism systems.


There's some fiddling to do it right if you use an expansion lens. That's why I usually leave it until I'm having an old movie might... a special occasion. But yeah, it works really well.