Through-The-Lens – Refers to a light meter built into the camera that measures light through the lens and single-lens reflex cameras that allow the photographer to see exactly what the lens is pointed at.
TLR – Abbreviation for “twin lens reflex”
Tonal Range – Various shades of gray between white and black.
Tripod – A three-legged post used for support heavy cameras during operation and minimizing blur during long exposures. May also be used for panning and tilting techniques.
TTL - Abbreviation for "through-the-lens".
TTL Meter – A light meter built-in cameras to provide accurate light metering directly through the lens.
Twin Lens Reflex - A camera having two separate lenses of the same focal length – one for viewing and focusing; the other for exposing the film. The lenses are mechanically-coupled so that both are focused at the same time.