Hey Everyone,

One on of the project galleries someone stated that you could use multiple fresnels together to shrink the focal length. Is this correct? Could we then shrink the length of the box in the simple plans just by using two or three fresnels?

Scott

Does anyone know if this really works? I might just have to buy another set of lenses to try it out

Scott

Hmmm. Just spitballing here, but even if it shortened the effective FL of the other fresnels, I don't see how it would shorten the FL of the triplet. i.e. the FL of the fresnels and triplet have to be in sync.

That's right, you can't change the focal length of the objective lens. If you could your throw distance would also decrease making the image even bigger.

Hey Brain,

I would just like to understand a bit more how the focal length matters, so i have anotehr question. According to GRA_PELAYO multiple fresnels will reduce the focal length of the fresnel. So what I was thinking is that this would allow us to move the triplet back (and allow us to shrink the box). I added a picture to show my point. To my non-scientific mind, it seems like this would be possible. The light at the triplet should be no different in either instance. Anyways if you could explain a bit more why this wouldnt work I would appreciate it.

Thanks,

scott

It's quite simple really. The projection lens can NOT focus at a shorter distance than its focal length, 320mm. The projection lens focuses on the panel and the panel alone. The fresnels have no bearing on the pj lens' focus.

Thanks Brain.

Scott