Quote Originally Posted by Ric Johnson View Post
On my 4x5 camera, the film back is 6 inches from the pinhole (f400). No drop off at all corner to corner.
Should only be slight less than 7" (sq root of 47) from the pinhole to the corner -- there will be some falling off of the light, but probably less than people usually burn down the corners/sides when enlarging standard negatives. Six inches should give about a normal view on 4x5.

I did hear about a fellow who use to sell pinholes -- the edges of the holes were actually micro-filed to a knife edge. No other info, I am afraid.