I have a few questions about how flash really works. Bearing in mind i shoot a canon EOS-1, so any technical advice should be given to that. Okay, as I understand it: Shutter speed has no effect on the exposure/duration of the flash. How then? does a flash determine how long to flash for? Okay, just say to make a correct (18% grey) exposure without flash, you need f3.5 at 1/15th of a second. How would you get your flash involved for a correctly exposed forground- if your priority was to keep the f stop the same? --->>> i imagine it would work like this: you meter (SOMEHOW?) with regards to the flash and then expose with a higher shutter speed - okay, fair enough. But what if you want the background exposed well too and your flash doesnt have enough range to do it - how then does it work. These are some basic questions, you can answer them, or, assuming this gives you an idea of what i do and don't know, you can just give general advice/rules. ALL help apreciated.