Regarding f-stops, another quick way to think of it is that they found by doubling these two series of numbers:
1 2 4 8 16 32 64 128 256 512 1024 2048... ( find more by doubling )
1.4, 2.8. 5.6, 11, 22, 45, 90, 180, 360, 720 ... ( find more by doubling )
So all the "standard" f-stops are found by alternating the values from these two lists.
When I make a pinhole camera, I often figure out which one of these numbers it is closest to, which gives a ballpark place to start for exposures.
But quite honestly, each camera is a little different ( internal reflections, shape of film plane, etc... ), and even though this calculation will be about right I always make a series of quick tests to get my "full sun" sunny 16 exposure by testing the camera. Then you can take that exposure and change it depending on the available light.
If nobody else has answered, I'll try to come back by and write how I make my pinholes. Gotta get back to work now!
Last edited by NedL; 05-06-2013 at 07:54 PM. Click to view previous post history.
Reason: I left out the number 16!