I'm trying to come up with a design for a circuit that can be used to accurately time the shutter speed of an SLR film camera. I'm basing it on this this project which uses a phototransistor and times how long it takes to go dark->bright->dark. I've got it working but I'd like to add more phototransistors to check consitency across the frame. I know I could just check them one after another in the main loop but given I want to be able to measure sub 1/1000 of a second exposures across multiple sensors I feel this might be too inaccurate. My first thought is to use hardware interrupt pins but I know that's not always the best design and hopefully some of the pins will be changing at the same time. So I was wondering what is the best general approach to measuring multiple inputs at high speed in this sort of situiation?
Would checking them all in the main loop be fast enough or is there some dedicated chip I could use that would solve this? I did think about using and RC circuit and then checking the charge of the capacitor after an exposure but I'd probably then get into the wormhole of having to calibrate for random components which I'd rather not do.