Latent image An image formed by the changes to the silver halide grains in photographic emulsion on exposure to light.  The image is not visible until chemical development takes place. 

Latitude:  The amount of over- or underexposure possible without a significant loss in the quality of an image.

Leaf shutter:  A camera mechanism that admits light to expose film by opening and shutting a circle of overlapping metal leaves.

Lens A piece of several pieces of optical glass shaped to focus an image of a subject.

Lens shade A shield that fits around a lens that prevents unwanted light from hitting the front of the lens and causing flare.  Also called a lens hood.

Light meter:  See exposure meter.

Light tight:  Absolutely dark.

Lith film:  A type of film made primarily for use in graphic arts and printing.  It produces an image with very high contrast.

Local reduction:  See reduction (3).

Long lens A lens whose focal length is longer than the diagonal measurement of the film with which it is used.  The angle of view with such a lens-film size combination is narrower at a given distance than the angle that the human eye sees.

Luminance The light reflected or produced by a given area of a subject in a specific direction.  Measurable by a reflected-light (luminance) meter. 

Luminance meter:  See reflected-light meter.