TTL Flash Metering
Automatic flash exposure in which the camera fires a brief preflash, measures the light returning through the lens, and sets the main burst accordingly.
Measured in
stops (EV)
In depth
TTL is fast and adaptive, which is why it dominates event and reportage work where distance changes constantly. It shares the weakness of every reflected-light meter: a dark suit or a white dress fools it, and the preflash can be confused by mirrors or by the subject blinking. Flash exposure compensation is the standard correction.
Examples in practice
Photographing a receiving line, TTL adjusts correctly as each guest steps closer to the camera.