I am wondering if there is a mathematical equation for working out shutter times and angles

for example if a shutter is set to 180 degrees and the camera is running at 24 fps then the exposure is 1/48th of a second, but say we increase the speed to 40fps we are exposing the film for 1/80th of a second how do i arrive at this conclusion what is the formulae for working this out, with different shutter angles and frame speeds. I have seen the charts but i think this would be good knowledge to have.

Warm regards,

Allyn

**Edited by Allyn Laing, 18 July 2006 - 12:41 AM.**