OK...
To take a photograph, you need to expose the film to enough light for it to work. The amount of light getting into the camera can be changed by opening the shutter for longer or shorter periods of time, and opening or closing the Iris - the appature (Also know as 'stopping' up or down).

A small appature (for some reason given a large 'f' number) means more of the pic is in focus. a wide appature, or small 'f' number means only the bit that you focus on (by mucking around with the lens) is crisp, and the rest is blured.

Now, with a pinhole camera your apature is fixed, and really small. so you don't really need to bother with trying to focus anything, cos a small appature means more will be in focus. What you need to do is open the shutter for long enough to get the light onto the film - with pin hole cameras this can take several mins. (Normall shutter speeds - the time shutters are open for - are between 1/30th and 1/500 of a second).

I really hope this hasn't been patronising but its just about all the theory you need to make an SLR work as a pin hole camera.

You will need to try out different exposure times (Bracketing as it s known in the trade) to get a good image.

Hope this helps...
(wirepimp, Tue 12 Apr 2005, 1:29, archived)