For a 4x5 image, 6.4 inches will give 1/3 stop fall off at the corners. 3 inches will give about 1 stop fall off. Regards, Bob... -------------------------------------------- "Do not suppose that abuses are eliminated by destroying the object which is abused. Men can go wrong with wine and women. Shall we then prohibit and abolish women?" -Martin Luther From: "Gregory Fraser" <Gregory.Fraser@pwgsc.gc.ca> > I went to a web site that had a calculator for the image circle diameter of pinhole setups. I calculated that a focal length of 3 inches would give me an image circle that would cover 4x5 inch film. I forget the pinhole diameter. Then I remembered how drastic the falloff is at the edges of pinhole images so I thought perhaps by increasing the focal length, I would have more of the brighter central part of the image and that would reduce the effects of falloff. 'But wait,' I yelled, 'if this were the case wouldn't Guy have been able to find a hotel room long enough to prevent the falloff he experienced in Montreal? Certainly someone as intimate with pinholes as Guy would know about that.' > > So, does the light falloff of a pinhole camera image follow an inverse square rule? Will it always be an issue no matter how big your shoebox, cigar tube or Quaker Oats box is?
