pin holes and ASA for exposure timesgreenspun.com : LUSENET : Large format photography : One Thread
I have a 4X5 camera which I would like to do some pin hole photography with. Does anyone have an experience with this. I think I know how to figure the f-stop, but I have yet to find a table or formula for working out the exposures for very small pin holes. Thanks in advance.
-- david clark (firstname.lastname@example.org), September 26, 1998
Try the Pinhole Resource Page, at: http://www.pinholeresource.com/ However, I wouldn't rely on charts and tables to calculate exposures. The only real way is to make tests.
-- Peter Hughes (email@example.com), September 27, 1998.
Just calculating the f-stop is easy: it's the hole-to-film distance divided by the diameter of the hole. A 1mm diameter hole, 200mm from the film, is f/200. If your meter doesn't go this far, write down the series 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45, 64, 90, 128, 181, 256... until you get there, and you can now work out the shutter speed & aperture combinations.
Film manufacturers give you reciprocity failure compensations, which you will need, but they may not go far enough. The great thing about reciprocity failure is that it compensates for over-exposure. So if you expose for 40 minutes when the correct exposure was 10 minutes, the film won't be 2 stops over-exposed.
But instead of all this theory, you could just spend 10 minutes knocking up a pinhole, make a few exposures, and see what happens.
-- Alan Gibson (firstname.lastname@example.org), September 28, 1998.