• Originally Posted by DWThomas
OK, I ran through some numbers ...

Typically a focal length equal to the diagonal of the film frame is provides a "normal" lens field of view.

Using the square root of the height squared plus width squared for a 6 x 7 frame comes out to about 9.3 cm = 93 mm for the frame diagonal dimension. The angle of view is about 53º.

Going into Pinhole Designer with a focal (pinhole to film distance) length of 93 mm, using 1.9, Rayleigh's constant, in the calculation, I get a pinhole diameter of 0.43 mm, which results in an effective aperture of f216.
If I use the constant of 1.6, which some folks use, I get a pinhole of 0.36 mm for f258...
I agree with your calculations, but have a couple remarks:

There is such a thing as a Raleigh's constant, but it has nothing to do with Pinhole photography:
http://hal.archives-ouvertes.fr/docs...97132C1135.pdf
I think what you're referring to is simply the square root of the Airy disc's diameter (square root of 2.44 or 3.66, respectively). One maximizes sharpness (2.44). The other maximizes resolution (3.66).

You correctly referred to the angle of view, which is calculated from the negative-format diagonal and the focal length, but we need to make sure that we are not confusing it with the 'actual' angle of view, which is highly dependent on the thickness of the pinhole material and responsible for the image circle? (see attachment)