fresnel use ?

[Err0r4o4]

I've read all I found on this forum to know why you r using a fresnel.. btw i'm new at this. I mean building projectors. I've owned 1 Infocus and 2 Panasonic but i did'nt know we could "build" one. okay so i'm I undersanding well that the fresnel is there only to be able to put the LCD to the farest position of the light to help from overheating ? Why not just isolate the light bulb in a room fully ventillated with a piece of glass between ?

 

[mhelin]

Wrong guess. Fresnels (two) are there to first collimate the light from the point source to parallel light rays that go through the LCD panel, then the other fresnel is there to condence the collimated ligh to one point close to the projector lens.

 

[Err0r4o4]

thanx a lot for this answer !!

 

[vudutek]

Fresnel questions

I've found these , which have an approximate 9" FL. Can anyone explain the pros and cons of using these over a 14" FL fresnel? Any benefit to using a matched pair of them?