Another idea I thought of, would using an old film camera lens work for a projection lens, assuming that the lens was in good shape (i.e.- no scratches on the lens elements)? If people have already tried this, I am sorry for posting a topic that has been already answered.

Probably not. What's the diameter and focal length?

Actually the more important question is what is the Image circle of the lens. For non photo guys that is sort of like asking what the Field of view of the lens is. for 15 inch lcd you need large format camera lenses and you will pay more then the pro triplet for them haha. They are much sharper then a triplet ofcourse but for our lcd its overkill.

Most 35mm camera lenses have focal lengths in the 30-50mm range and are optimized to get a good picture on a 42mm image circle with is just too too too narrow even for a small LCD.

So basically my best bet is to get a standard projection lens (from LL or spare part from another projector)...hm. even if the setup was like so:Click to view attachment

is this even feasible?

not even sure what your trying to show. what is the green blob on top of the blue stick?

Is the lcd in the middle?

Okay... This is kind of backwards...

Assuming that the "green blob on a stick" is a tree, that's more a description of the photographic process, and not so much projection. (Unless you're projecting an image of a tree. )

The problem here is the size of the LCD, and the distance between it and the lens. For a photographic lens, the LCD would need to be small, ie, the size of a 35mm negative, maybe a tiny bit larger. It also would need to be much closer to the LCD than we could allow. Camera lenses are a completely different scale of focal length.

For example, a regular camera lens is about 28mm focal length. A general purpose zoom lens (Such as I use for regular snapshots) will be 28-50mm. A telephoto lens might go as high as 120mm, but certainly not more. The standard LL triplet, on the other hand is 320mm. The pro lens, which gives the projector a good throw is even longer at 500mm. This is a completely different scale.

So unless you have some serious cash to invest in the lenses, and can find 1.5" LCDs around somewhere, this isn't going to work so well for a projector. The GOOD news is that if you could find these things, you could probably manage with no fresnel lenses at all.

A CRT lens has been done before http://www.lumenlab.com/forums/index.php?showtopic=6722&st=0 But I don't think a camera lens has.

Thx for all the info