I just tested iKspozher (weird name) a program for the iPhone. Which calculates correct exposure for a given setting of scene, ISO and aperture/shtter speed. It works very well, all nature photographers should check out the program.. its a must have! http://venkykrishnamani.com Check out iFotobacus as well, for $0.99 its a steal, there are other programs like Photocalc, and DOF calculator but they are priced @ $2.99 and I don't use most of the features they offer except for hyper focal distance calculations for which purpose iFotobacus does a great job. NOTE: Photocalc esp doesn't have keypad input for distance/focal length input which is annoying.