TTL Abbreviation

TTL stands for Through The Lens metering. The TTL metering system meters the light that comes through the lens, bounces off a mirror and onto a sensor inside the camera.

There’s also TTL flash metering. It’s a type of flash exposure metering that is used to measure the flash light that reaches the sensor when the camera’s shutter is open. When the needed amount of light is detected by the camera, the latter instructs the flash unit to shut off.