Quote Originally Posted by wildbillbugman View Post
. . . I have been working with some of the online pinhole calculators, But their are signifigant diffrences in the "optimal" pinhole diameter for each wavelength, given a constant focal length.
Pinhole Designer lets one choose Lord Rayleigh's constant, first Fresnel zone constant, or a user constant. The first two yield pinholes rather larger than optimum for on-axis sharpness. Many of us prefer a 1.5 or 1.4 user constant. The larger constants may sacrifice a little on-axis sharpness for improved off-axis sharpness, and reduce exposure time slightly. This has often been discussed on http://www.f295.org/Pinholeforum/forum/Blah.pl?