Stopping down

Changing the lens aperture to a smaller opening. For example, from f/8 to f/11.

Telephoto lens

A lens that makes a subject appear larger than does a normal lens at the same camera to subject distance. A telephoto lens has a longer focal length and narrower field of view than a normal lens and have a shallower depth of field than wide angle lenses.

TTL

Through the lens

TTL focusing

Viewing a scene to be photographed through the same lens that admits light.

TTL viewing

In a single lens-reflex (SLR) camera the view seen through the viewfinder is that seen through the lens.

TTL Metering

The light meter built into the camera determines exposure for the scene by reading light that passes through the lens during picture-taking. SLR cameras have built in meters which measure light after it has passed through the lens, a feature that enables exposure readings to be taken from the actual image about to be recorded, whatever the lens angle of view and regardless of whether a filter is used or not.

Vignetting

Underexposure of image corners produced deliberately by shading or unintentionally by inappropriate equipment, such as unsuitable lens hood or badly designed lens. A common fault of wide angle lenses, owing to reflection cut-off of some of the very oblique rays. May be caused in some long-focus lenses by the length of the lens barrel.

Wide angle lens

A lens that has a shorter focal length and a wider field of view (includes more subject area) than a normal lens.

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