Quote Originally Posted by Rlibersky
Has anyone built a LF pinhole? I have some film that is 10.5in x 120ft. I am thinking of building a 10.5x18 inch camera. My question is should I make it so the film plane at the same distance from the pinhole on a circle or flat like it would be in a normal camera. When I 've used shorter length, ~300mm, pinhole on my 8x10 the edges seem to get distorted. Was this a function of a badly made pinhole?
Depends what you want. If the film is flat, you'll get the exact same geometry you'd get with a perfect lens and the same relationship of film plane to scene -- that is, if the film is parallel to the front of a building, you'll get no convergence in either verticals or horizontals. However, that looks very unnatural with extremely wide angles, because you're used to moving your head to view angles that wide and in doing so, your brain automatically compensates for the convergences.

If you use a very wide angle, however, you'll also have significant exposure fall-off at the edges and especially corners of the frame; curving the film so the pinhole is at the center significantly reduces this fall-off, though it introduces distortion that, while looking very "normal" at the edges, leaves a strong curvature in what should be straight objects that cross the frame.

Since pinhole cameras are so easy to make, why not do both? You can make a semicircular camera from a large popcorn tin or two gallon bucket, and a flat one from a wood box with a suitable film retainer in the back, and then see which you like. I'm betting you'll like both, for different things...