It depends on the size of the beam. 4''x6'' should be fine for
most PJ's. Just put a white paper in front of the lens and measure
the size of the rectangle.
where are you planning to get the prisms?
If you are getting those plaques from massillon plaque, dont waste your money.http://www.massillonplaque.com/produ...4&productid=85
I just got the 5''x7''. it is almost like mirror finish and gives too much reflection.
Even if this prism is coated it may not be good as they probably have polished
it like a mirror purposefully.
Even if you get it from elsewhere in US like crystal factory it might be the same
as it might come from the same glass manufacturer. These online places are
I have not yet seen posts from any one who bought the prisms from crystal factory
and got them coated.
I have ordered a set of prisms from Sam. They are much smaller. have to
wait and see how they perform.
The image quality will not be bad but the main drawback of the DIY
lenses is the reflection from those uncoated prisms.
Those massillonplaque prisms also put reflections right on the image.
Didnt mean to be discouraging, just my experience.