> By chance, I photographed a needle and projected it, > only to find it had 2 different angles of taper and > the diameter was different everywhere along the length > of the needle! Checked a lot more needles and found the > same thing. The question: where on the needle does the > diameter from the much published chart of needle > size / diameter apply? If this chart turns out to be > mythological, it will only increase my esteem for the > inexact art of pinhole photography.
Needle? You shouldn't be using needles, you must use pins!, after all, that's why it is called pinhole photography. :-) I get my needles from "The Dollar store" and they are very consistent from where the tapering of tip starts to about where the needle's eye is (not that it matters to me, tho, as I measure my pinholes and zone plates with a microscope). BTW, needles I buy are uncalibrated, I measure my pinholes with a microscope. Alternatives ways to measure pinholes have been discussed in the past, tell us if you need help with that. Guillermo
