Sorry if this is a dumb question. I also didn't find a similar in search. On the exposure calculation, there are fn, shutter speed and iso. Also flash / light meters gives you the fn and speed for a given iso. However light intensity drops drastically with distance. It may not be a problem for ttl metering since it measures amount of reflected light from the subject that reaches the camera but using a flash meter reads the light hitting the subject and gives you a set of fn and ss regardless of where the camera is located. Why is it so? I've seen a lot of photographers that take a measurement from under the chin and then move around, how is this a proper metering?