E-TTL flash exposure system and wireless control with optional Speedlites
E-TTL Autoflash System
E-TTL (Evaluative Through-The Lens) autoflash is Canon's most advanced flash metering system. It is featured in the latest EOS cameras and Speedlites (EX series). With the EOS-3, the E-TTL autoflash system uses a 21-zone evaluative metering sensor to obtain natural looking, balanced flash pictures.
Three variables are taken into account to determine the optimum flash exposure:
1. Ambient light reading
2. Preflash reading
3. Focusing point-weighted reading
After recongnizing the scene's brightness distribution and subject position, the camera calculates the proper flash output for the main flash. With non-E-TTL EOS-dedicated Speedlites, the EOS-3 uses off-the-film A-TTL or TTL 3-zone flash metering.