In photography, through-the-lens (TTL) metering refers to a feature of cameras whereby the intensity of light reflected from the scene is measured through the lens; as opposed to using a separate metering window or external hand-held light meter.
Non-Nikon brand flashes bypass the TTL BL Zoom Problems
Basics Note: The flash menus generically say TTL (Through The Lens metering), but the Nikon system specifically actually defaults to be TTL BL (balanced flash mode). There is also a regular...
How to Understand the Difference Between TTL Versus Manual Flash...
A TTL enabled flash fires a "pre-flash" before the actual shot is taken. The camera then measures the pre-flash with the ambient light level to calculate the power needed from the actual flash to make a...