F STOP

Definition: number that equals the focal length of the lens divided by the diameter of the aperture.

F-NUMBER

Definition: The number resulting when the focal length of a lens is divided by the diameter of the aperture. A sequence of f-numbers calibrates the aperture in regular steps (know as stops) between the minimum and maximum openings of the lens. The f-numbers generally follow a standard sequence, in such a way that the interval between one full stop and the next represents halving or doubling in the image brightness. Also called f-stop or relative aperture. The f-number becomes progressively higher as the aperture is reduced to allow in less light; i. e. f/5. 6, f/8, f/11, f/16, f/22, f/32. . . Theoretically, all lenses at the same f-number produce images of equal brightness.

Definition: A number that indicates the size of the lens opening on an adjustable camera. The common f-numbers are f/1. 4, f/2, f/2. 8, f/4, f/5. 6, f/8, f/11, f/16, and f/22. The larger the fnumber, the smaller the lens opening. In this series, f/1. 4 is the largest lens opening and f/22 is the smallest. Also called f-stops, they work in conjunction with shutter speeds to indicate exposure settings.

F-STOP

Definition: A number that indicates the relative size of the opening of the lens (aperture) and written, for example, as f/16. Because the number is obtained by dividing the focal length of a lens by it's effective aperture, the larger the aperture, the smaller the f-number. In the conventional series, each number represents an aperture that admits half as much light as the preceding one. Thus f/16 lets half as much light as a lens opened to f/11.

Definition: The common term for the aperture setting of a lens. see also f-number.

FACTOR

Definition: See filter factor

Definition: number that tells how many times exposure must be increased in order to compensate from loss of light.

Definition: A number that tells how many times exposure must be increased to compensate for loss of light (for example, due to use of a filter).

FADING

Definition: The loss of or change of colour density, generally accelerated by exposure to sunlight.

FAHRENHEIT SCALE

Definition: scale of temperature named after its German originator, G. D. Fahrenheit. On this scale, the freezing point of water is 32° F, and the boiling point of water is 212° F.

FALLOFF

Definition: Decrease in the intensity of light as it spreads out from the source.

FALSE ATTACHMENT

Definition: part of one object seen behind another so that lines, shapes or tones seem to join up. A composition device used in various ways to produce images in which foreground and background objects appear to occupy the same plane.

FARMER'S REDUCER

Definition: used for bleaching negatives and prints. See reducers

Definition: A solution of potassium ferricyanide and sodium thiosulfate that is used to decrease the amount of silver in a developed image.

FARRADAY SHUTTER

Definition: high-speed shutter using a pair of crossed polarizers, between which is a glass block within a coil. When a voltage passes through the coil, the plane of polarization changes, allowing light to pass through the second polarizer.

FAST

Definition: Describes 1. a film or paper that is very sensitive to light; 2 a lens of wide maximum aperture, relative to its focal length, allowing maximum light into the camera in minimum time. The speed of a lens - its relative ability to take in light - is an important measure of its optical efficiency: fast lenses are more difficult to design and manufacture than slow lenses, and consequently cost more. ; 3. a short shutter speed. Opposite: slow.

FAST FILM

Definition: Film which has an emulsion that is very sensitive to light. These film have high ISO ratings.

FAST LENS

Definition: Lens with a wide maximum aperture (low f number).

FAT

Definition: File Allocation Table. A table that an operating system maintains on a hard disk that provides a map of the clusters that a file has been stored in.

FEATHERING

Definition: A technique in many image editing programs that allows for the softening of the edge around a selection.

FERRIC CHLORIDE

Definition: bleaching solution used on negative materials.

FERROTYPE

Definition: To give a glossy printing paper a very high sheen by drying the print with its emulsion pressed against a smooth metal plate, usually the hot metal drum or plate of a heat dryer.

FERROTYPE PROCESS

Definition: method of creating direct positive images with dark enameled metal plates as a base. Also known as the tin-type process.

FIBER BASED PAPER

Definition: photographic paper without a resin coating. Processing times are longer than for other papers, but the paper is more archivally permanent.

FIBER OPTICS

Definition: An optical system that uses glass or transparent plastic fibers as light transmitting media. These cables have greater bandwidth than electrical transmission through wires.