PVC fresnel seem to come at a fraction of the price of traditional Acrylic based ones. Does anyone know how they perform in comparison? I can't find much more info about them. They are listed for less than $2 on 3DLens.com.

In my experience I have found that they never can go quite flat, I mean they bend and they have a permanent bend in them, not sure how to explain this better...I had two of them though so I'm sure it wasn't just a faulty one. You could always try, I mean they probably will look like crap, but for 2$'s a fresnels you can't lose, except that 10+ dollar shipping from 3dlens.com Check the search for them and maybe you will get some info about it.

Thanks. Did they bend after use or were they bent from the start? They may have a lower operating teperature compared to Acrylic ones. Did you use tempered glass in your arrangement?

I have yet to actually make my projector, but I have a few PVC fresnels, and a couple misc acrylic ones. Yes they came bent, I'm not sure if it matters or not its just they don't go perfectly flat like the acrylics do.

It is a page magnifier. Do not build a projector with page magnifiers.

Unless its a small screen, like the PS1 LCD.

Even then, the tiny amount that you save costs you so much in terms of light quality, it's hard to justify.