Photographic Terms

Albumen photograph
An image created using a silver halide (a silver-containing compound) as the light-sensitive agent and egg whites (albumen) as the binder.*

Baryta paper, fiber-based paper
A photographic paper base with an intermediate layer of barium sulfate suspended in gelatin, sometimes with optical brighteners

Cellulose acetate base or support
A plastic photographic support material made from cellulose (wood pulp or cotton) broken down in water and dissolved in acetone. It replaced chemically unstable cellulose nitrate.

Cellulose nitrate base or support
A plastic photographic support material made from a mixture of cellulose and compounds that include nitric ester. It replaced the glass used in earlier photographic negatives. A highly unstable and flammable material, it was banned in 1951. Cellulose nitrate-base film must be identified and stored under stable conditions.

Chromogenic dyes
Yellow, magenta (purplish-red), and cyan (greenish-blue) dyes used to create color photographs.

Cibachrome print
A color print made from a color transparency in a positive-to- positive process. The image is printed on paper that has the dyes incorporated into the emulsion of the paper, instead of being formed chemically.*

Colloidal silver
Very fine silver particles suspended in a medium, such as gelatin, that produce a colored appearance.

Collodion print
A photographic print that uses collodion (cellulose nitrate dissolved in ether) as the emulsion that holds the light- sensitive salts to the base.*

Color transparency
A positive color image photographically produced on transparent film or glass and viewed by transmitted light, usually via projection. Examples are Kodachrome and Ektachrome.*

Direct positive
A positive image made directly in the camera, such as a daguerreotype, ambrotype, or tintype.

Fiber-based paper
A paper base coated with a light-sensitive chemical formula used for making fine photographic prints.

Fixing
A chemical process intended to eliminate residual photosensitive salts. After the fixing bath, the image is stable and may be viewed in light without undergoing alteration.

Gampi paper
Paper made from the bark of the gampi bush (Wikstroemia sp.), which is found in the mountainous, warm areas of Japan.

Gelatin
A protein extracted from animal matter that is used as the basic binder in photographs.

Gelatin dry plate negative
A photographic negative with an image formed from metallic silver in a gelatin emulsion on a base of glass.

Gelatin emulsion
A layer in film or prints of light-sensitive salts in a gelatinous substance (see Silver emulsion).

Gelatin printing-out paper
A photographic paper in which the base is made of gelatin and the image is formed through the action of light alone; no chemistry is used.

Glass plate negative
A photographic image that uses glass as a base and in which the image appears reversed and has tones that are the reverse of those in a photographic print made from the negative.

Holland Van Gelder paper
A heavyweight paper used for etching (like photogravures) produced by the Van Gelder Company.

Image binder
The component of a photograph, such as albumen, collodion, gelatin, or synthetic polymers, used to hold and suspend the image material above the support.

Image material
The material that creates the image in a photograph; can be metal, pigment, dye, or ink.

Negative
A photographic image, usually on transparent film or glass, with tones that are the reverse of those in a photographic print.

Oxidation-reduction
The chemical reaction that is the basis for the chemical development of photographs. As it oxidizes, the developer solution reduces silver halides (silver-containing compounds) that have been exposed to light and changes them into metallic silver.

Photogravure
A photographic image produced from an engraving plate by a three-step process that includes taking the picture, producing a printing plate of the image, and printing the image on paper.

Platinum print
A print made with platinum instead of silver.

Positive
An image on either an opaque or transparent support that appears as we see it.

Print
A positive image on an opaque support.

Printing-out paper
Photographic paper on which the image is formed through the action of light alone; no chemistry is used.

Silver emulsion
Suspension of silver halide (a silver-containing compound) in gelatin, which, when applied to a substrate, constitutes the photosensitive layer of a photograph (see Gelatin emulsion).

Silver gelatin
A photographic print, negative, or transparency with an image formed from metallic silver in a gelatin emulsion on a base of paper, plastic film, glass, or other material. A silver gelatin photograph usually has black-and-white tones. It was the main photographic process after the 1890s.

Silver halide
Light-sensitive crystals used to make photographic film and prints. When the crystals are exposed to light, a chemical reaction darkens the film to produce an image.