You may have seen my previous inquiry regarding projecting a movie through
achromatic lenses.

I've run into a snag. When I put the achromats together in the path of the
projected image and bounce it off a mirror, I see an image that fits nicely
within the boundaries of the lens diameter. Looks sharp, clear.

However, I find that when I align my camcorder at about the same place my
eyes were, it won't bring the image into focus even if the zoom on the cam
is pulled all the way back  - i.e. the focus point is outside the range of
the cam's ability to focus unless I move the camera way back, but doing this
yields a very small image in relation to the field of view of the camcorder.
Fiddling with the focus on the projector doesn't help other than making it
less out of focus if it's a point where the image looks sharp to my unaided
eye.

I find that if I extend the distance between the projector and the
reflecting mirror without moving the achromats, it's getting closer to
focused, but don't have enough room where it is to move it farther back, so
I plan to set up all the components where I have more room to see how far
apart they need to be to get a sharp focus at the size I need. The distance
the achromats are from each other seems to have a bearing as well. Closer
together seems better.

Obviously some issues at work here that I'm unfamiliar with. Didn't have
this problem when projecting through a condenser lens - I could zoom the
image larger or smaller with the projector and easily find a focus point no
matter the size of the image. Didn't even have to be particularly picky
about how far the condenser was from the projector. I thought if the image
looked focused to my eye, the cam would also see it the same way since I'd
never encountered a situation where it wouldn't. But this is clearly not
universally true.

Another issue that no doubt is related to this. The FL on these lenses is
supposed to be 235mm. What exactly does that mean? I thought maybe this was
the distance at which you would see a focused image but I can look through
either or both lenses and see in focus images of things at varying
distances. Someone mentioned that if I use two lenses, I can cut the FL in
half. If so, to do this, how far do they need to be from each other?

All input is appreciated.