• Originally Posted by RalphLambrecht
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)
Enh, this is how the world works .... maybe another decade or two of instant worldwide communications will clear some stuff up. In Pinhole Designer, there is a pull-down for that constant value. One of the choices is "1.9 Lord Rayleigh." I was under the impression that he gets credit for the number, but can't say I've ever delved into it at any detail and may have misspoken. Anyway, perhaps I should say:
One popular magic constant is 1.9
That is a good point about the angle of view business. The numbers I posted were from using Pinhole Designer, but I'm sure it is based on the "perfect pinhole," an infinitesimally thick sheet of absolutely opaque non-reflective material with a perfectly round hole (since it's infinitesimally thick, it's got a knife edge for sure. As anyone who has tried it well knows, the ideal is only a goal and some of us don't get anywhere close to it. And at the minimum, the light fall-off is an issue of the hole becoming a narrower and narrower ellipse viewed from an angle off the pinhole to film axis, eventually a (closed) line at 90º. But that too can be complicated by the actual fabrication.

Anyway, the calculations I suggested above were to illustrate my approach to the original poster's question. You have to pick some basic parameter(s) and work out the rest. When I did my pinhole body cap for the SQ-A, the film format and film to pinhole spacing were pretty much fixed, so there was no point in agonizing over angle of view calculations, other than to learn what it was.