DIY Lens angle

There is no actual fast rule for this as the exact angle for the prism rotation is based on the angles of the prism themselves and the throw ratio of the set up. Example, if you set up a lens using prisms for a short throw, the decide to increase the throw ratio, you will need further rotation for the longer longer throw. This happens mainly because of grid distortion.

The best you can do is to make a 2.37:1 screen, then project your 16:9 image (top to bottom is framed, left to right is centered), then add the prisms and rotate until you get the edges aligned.

+1

If I may, my friend just put together his DIY lens and if his 16.9 pic is set correctly and he slides the lens in front, his 2.4 pic is now two inches below. Does he have his prism angles incorrect or is it just as simple as tilting the lens to fix it?

He said he lined up the 16.9 pic perfect and worked off that to set his prism angles, but maybe when solidifying the prisms they got skewed?

John

My friend flipped the lens unside down and all aligns perfectly.