Am looking at building a projector using a 17" panel... have got an overhead projector i can use to pull off the triplet / lightsource etc etc... but of course i'll need bigger fresnels... the focal length of the triplet is 316mm, but the pro fresnels sold here have a foca length of 600mm... so are these parts entirely uncompatible? or do i just use the fresnels focal length and put a gap of 600mm between the Fresnel and the center of the triplet?

on another note...
has anybody found a 17" (or even a 15") monitor that does uxga (1600x1200) natively?
i can't find any that do

bump - anyone?
can i just ignore the rear focal length of a triplet and apply the focal length of the fresnel?

The field (front) fresnel has to be matched to the projection lens. It is usually a 330mm ƒ field to 320mm ƒ triplet. For your 316mm triplet, you want something like a 326mm ƒ field fresnel. You can get this, but your throw using a 17" panel and a 316mm ƒ triplet is going to be very short; better suited to rear projection. You'll also notice that your triplet can barely resolve the corners of your LCD. The pro lenses were made to solve this problem.

mmkay, so to use the pro fresnels i'd need the pro lense... *looks in wallet* *sigh*

future upgrade i guess...

So how does one calculate if a fresnel matches a triplet?
When looking for parts this would be nice to know.

Download the program here:

http://www.lumenlab.com/forums/index.php?showtopic=7912

I am not sure that does it...

The fresnel need to match the triplet correct? angle of light going in and out.

This just calculates what the focal length should be at a given distance with a given lcd etc... that is, if I understand correctly.

With this calculator I can get a 500mm triplet to match a 330mm fresnel just by adjusting the screen size or the throw distance.

Basically I just need to know if I can use a Fresnel with:Focal length: 550mm and the pro triplet.