>>Does use of a 2.35:1 lens like yours reduce the brightness of the projector? I mean, I wouldn't expect it to be noticable or anything, but when you use a 2x teleconverter on a camera, the effective f-stop changes. Maybe it's a different principle.
Good question. It took me a while to get my head around it... in fact after a couple of attempts I am on the verge of giving up and waiting for Randy to answer.
The short answer is "if you zoom out so the 2.35 image ends up the same width it was before you added horizontal stretch from the lens and vertical stretch from the projector/player, then the image is actually BRIGHTER than before because you are using all of the LCD panel rather than just the middle 3/4.
I imagine that if you just stick the lens in front and make the image wider then it will be less bright, exactly as you would expect.
The trick is that you do a number of other things at the same time, none of which can be done without the lens, and the result of all those actions together is a sharper, brighter 2.35 image.
EDIT -- you can tell this isn't simple -- I had to edit my own post three times before it was what I considered "readable". Hint -- if you think about a vertical compression lens rather than a horizontal expansion lens it's a bit easier to grasp, even if the trend seems to be towards horizontal expansion lenses these days.
FWIW, I think the big advantage of vertical compression lenses is that if the projector is already mounted you don't need to move it or change the zoom settings. Many projectors still don't have the 1.33 zoom range you need to compensate for the horizontal expansion, and even the ones that do are rarely mounted in a position where you have enough unused zoom range.
Last edited by bridgman; 09/04/06 06:14 PM.
