I wanted to build my projector using unsplit optics because I heard it results in a much brighter picture.
I would need to adjust for keystone using lens shifting and was wondering whether the lens shifting would reduce the brightness of the picture so much that I would get better results by using split optics and tilting the collector fresnel. Has anyone had any experience with this?

Check here I do not believe that you can keystone with a one piece setup, you have to use a split setup to do keystoning.


I could be wrong but that is how I read and understand the guide.

i wass thinking to make an unsplit to, but iff im correct, shifting the lens will give you loss of brightness...
so you can better use a split,
except, when you have an nvidia vga card, then you could do keystoning by software....
but i have ati, so, cant say it for sure...

I'm using lens shifting to fix the keystone effect with my projector. I don't recall ever hearing that you'll get a brightness loss by using lens shifting. One thing you will get is an off center "hot spot". You can alleviate this by shifting both lenses (I'm pretty sure that's the theory at least). My projection's hotspot seems to be a little lower than center, but this could be because of my viewing angle to the screen as well. My screen is a Da-Lite "High Gain" which is very angle dependent. Also, the off center hotspot is probably not any more noticeable than the centered hotspot that you'd get anyway.

Also remember that using software keystone correction will fix the distorted shapes, but will not fix the focus. Lens shifting produces a straight image with uniform focus.

What do you mean by "shifting both the lenses"? I thought lens shifting just moved the projection lens and the lamp.

To do lens shifting you actually shift one or both of the lenses upward or downward. What you're doing is moving the focal point up or down...

The projector wiki (which I'm pretty sure is not a wiki...) has a pretty good write up of lens shifting...