Reflex cameras contain a photocell, although sometimes more than one, inside the housing of pentaprism that measure the screen image brightness. The exposure reading is dependent upon the amount light passing through the camera lens, hence the name (TTL metering) which provides for close-up exposure adjustments, angle of view, vagrant
illumination, and other factors of the lens. A few TTL systems redirect... or in photography
terminology: (Automatic metering control ).
Cameras featuring through-the-lens (TTL) exposure metering and including hand-held meters aimed directly at a scene measure the average mirrored intensity of light which yields dependable exposures for scenes containing average distribution of contrast and brightness. Subjects containing extreme contrast or incredibly bright or areas
dominated by darkness need additional exposure.
Single-lens reflex cameras (SLR) most often come to mind when thinking of through-the-lens metering. A light sensor may be fitted inside the pentaprism (or perhaps a pentamirror) whatever the case may be and employed to create an upright image incorporating the scene the lens sees. Although, TTL metering has been integrated into other camera types.
TTL flash metering happens after the opening of the shutter. subsequently sensors take note of the amount light created by the flash coming back through the lens of the camera shuts off the flash automatically ("quench") when the correct light amount has been created.
Mar 3, 2014