Glossary

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Factor:  a number that tells how many times exposure must be increased to compensate for loss of light (for example, when using a filter on the lens)

Farmer’s Reducer:  a solution of potassium ferricyanide and sodium thiosulfate that is used to decrease the silver in a developed image

Fast: describes 1) a film or paper that is very sensitive to light, 2) a lens that opens to a very wide aperture, 3) a short shutter speed. Opposite: slow

Fiber-base paper:  formerly the standard type of paper available, now replaced to an extent by resin-coated papers.   The optimum paper for longevity of prints, and best choice for exhibition quality prints

Fill light:  a source of illumination that lightens shadows cast by the main light and thereby reduces the contrast in a photograph

Film plane:  see focal plane

Film speed:  the relative sensitivity to light of a film.   Several rating systems are used: ISO (most common in the U.S. & Great Britain), DIN (common in Europe), & others.  Film speed ratings increase as the sensitivity of the film increases

Filter:  1) a piece of colored glass, plastic, or other material that selectively absorbs some of the wavelengths of light passing through it.  2) To use such a filter to modify the wavelengths of light reaching a light-sensitive material

Filter factor: see factor

Fixer:  chemical solution (sodium thiosulfate or ammonium thiosulfate) that makes a photographic image insensitive to light.   It dissolves unexposed silver halide crystals while leaving the developed silver image.  Also called hypo

Flare: unwanted light that reflects & scatters inside the lens of a camera.  Upon reaching the film, it causes a loss of contrast in the image

Flash:  1) a light source, such as a flashbulb or electronic flash, which emits a very brief, bright burst of light. 2) To blacken an area in a print by exposing it to white light, such as from a penlight flashlight

Flash meter:  an exposure meter that measures the brightness of flash lighting to determine the correct exposure for a particular setup

Flat:  a scene, negative, or print with very little difference in brightness between light and dark areas. Opposite: contrasty.  Also see: reflector.

Floodlight: an electric light designed to produce a broad, relatively diffused beam of light

f-number: a number that equals the focal length of a lens divided by the diameter of the aperture at a given setting.  Theoretically, all lenses at the same f-number produce images of equal brightness.   Also called f-stop or relative aperture.

Focal length:  the distance from the lens to the focal plane when the lens is focused on infinity.  The longer the focal length, the greater the magnification of the image

Focal plane:  the plane or surface on which a focused lens forms a sharp image.  Also called the film plane.

Focal-plane shutter:  a camera mechanism that admits light to expose film by moving a slit or opening in a roller blind just in front of the film  (focal) plane

Focal point:  the point on a focused image where the rays of light intersect after reflecting from a single point of a subject

Focus: 1) the position at which rays of light from a lens converge to form a sharp image. 2) to adjust the distance between lens and image to make the image as sharp as possible

Focusing cloth:  a dark cloth used in focusing a view camera.  The cloth fits over the camera back & the photographer’s head to keep out light and to make the ground-glass image easier to see

Fog:  an overall density in the photographic image caused by unintentional exposure to light or unwanted chemical activity

Frame: 1) the edges of an image. 2) a single image in a roll of film

f-stop: the common term for the aperture setting of a lens.

Full-scale:  describes a print having a wide range of tonal values from deep, rich black through many shades of gray to brilliant white

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