I found a neat little program for the iphone... called pinhole assist. it's $1.99

With "Pinhole Assist"

Compute exposure time ;
Measure light;
Enter your camera aperture from the predefined list or compute it;
Let the assistant automatically compensate for reciprocity of film (correction for long exposures), or use your own curves.


http://itunes.apple.com/us/app/pinho...7473?mt=8&ls=1