----- Original Message ----- From: "stephen" <ifstep...@yahoo.com>
> hi phillip I am not Phillip, but pls allow me to try to answer your question: > curious to know what are you using to create the > pinhole? > or do you know the approx f/stop? > well, that is the question isnt it? > so many different charts have this or that f/stop > assigned to a fixed sized. > so has anyone come accross an 'accurate' mm (or inch) > to f/stop guide? There are several ways to find the f/stop of your pinhole camera set up. One method is to shoot an "average" scene under a sunny day, bracket several exposures and record the different times, process the film and select the "best" exposure, then find the f/stop of your pinhole making use of the fact that under sunny skies f/16 @ 1/iso seconds is the "correct" exposure. Another method is by knowing the diameter of your pinhole, then the f/stop will be given by the quotient of the distance between pinhole and film and the diameter of the pinhole. The hard part is measuring the pinhole. Knowing the diameter of needles you use to make the pinholes is a way to get an approximate size of the pinhole, measuring the pinhole itself is even more accurate. I wrote a small article on how to measure pinholes using your cheap (mine is anyway) flatbed scanner, what you then do is make a bunch of pinholes, measure them and use the one that approximates best to what you need. Here is the link to the small article: http://members.rogers.com/penate/diameter.htm > where can i get a #10 (0.46 mm/0.018 in) needle? > thanks! I know the following doesn't answer your question directly, but it may, indirectly: If you own a dremel or similar drill, you could also use wire gauge drill bits, a wire gauge drill bit #77 is 0.018" exactly what you need. see this 2 sets, for instance: http://www.mytoolstore.com/irwin/numbers.html there may be cheaper sets out there. Guillermo
