Pinholes used in these cameras are manufactured from 0.025mm (0.001") stainless steel and accurately micro cobalt drilled. The resulting pinholes are very clean and circular. See microscopic photo below:

Pinhole sizes and focal lengths are calculated using Pinhole Designer based on the following formula:
d = c
f x l
d = pinhole diameter
c = constant (1.59)
f = focal length
l = light wave length (0.00055)
The constant (1.59) accords with the pinhole edun specification and cameras built on this formula produce clean clear sharper images. This constant gives a different result to the Lord Raleigh constant of 1.9.

The tables below detail the specifications used in the construction of 4x5 and 10x8 cameras: