Lighting
Metering Flash: Understanding TTL vs Manual
Every external flash operates in one of two modes: TTL (Through The Lens) automatic metering, or manual power control. Understanding when each mode is appropriate, and how to meter effectively in both, eliminates the most common flash exposure problems. How TTL Works TTL metering fires a pre-flash, an extremely brief burst of light, milliseconds before the actual exposure. The camera’s meter reads the light reflected from this pre-flash through the lens, calculates the flash power needed for correct exposure, and sets the main flash output accordingly.