Quote Originally Posted by Nick Kanellos
Quote Originally Posted by michaelbsc View Post

What function describes the image's circle of confusion from the diffraction and the CoC from just the hole?


MB
d=1.56√λf

where
d = the pinhole diameter
λ = the wave length (about 0.000555mm)
f = the focal length

Taken from "Way Beyond Monochrome. 2nd ed." p. 155
Is this the Formula for an optimum size?