Background

The most remote portion of a landscape, or the space and objects behind the principal figures. In portraiture an artificial background is made of plain or painted cloth, canvas, or stout paper, fastened, for convenience, to a wooden frame on rollers.

Revolving Background

A form of background circular in construction, which can be revolved on a pivot until the correct light and shade effect is obtained back of the sitter.

Worked-in Background

The process of building on the negative or print (usually the negative) a background effect. Full instruction is given in the above reference.

Backing for Plates

(See Plates, Backing for.)

Backing for Prints

(See Prints, Backing for.)

Balance

(a) An instrument (scales) for determining the relative weights of materials. (b) A term used to describe an artistic combination or proportion and arrangement in a picture.

Canada Balsam

Balsam of Fir; Balm of Gilead (improperly); Canada Turpentine.

Yellowish, transparent, solid mass; pine-like odor; bitter taste. Soluble in ether, chloroform, benzene, oils, etc. Used for cementing lenses, attaching cover-glasses to lantern-slides, mounting microscopic objects, etc.

Barium Bromide

BaBr2 + 2H2O.

Colorless, tabular crystals. Soluble in water, alcohol and ether. Poisonous. Used sometimes in collodion.

Barium Chloride

BaCl2 + 2H2O.

Colorless, flat, four-sided crystals; bitter, salty taste. Poisonous. Soluble in 2.5 parts water; almost insoluble in alcohol. Used, sometimes, in the preparation of sensitized papers, instead of the more commonly used chlorides.

Barium Nitrate

Ba(NO3)2.

Lustrous, colorless crystals, or white powder. Poisonous. Soluble in 20 parts cold, 2.8 parts boiling, water; insoluble in absolute alcohol. Used as a wet-plate developer together with ferrous sulphate, and serves to prevent pinholes.

Barium Sulphate

BaSO4.

Heavy, white powder. Soluble in ammonium-nitrate solution; insoluble in water and acids. Used in the manufacture of transfer paper for the carbon process; also in the forming of an emulsion to coat paper.

Bas-Relief Photographs

Prints in relief, obtained by either handwork on the back of the print while damp, or by the action of light on a thick film of bichromated gelatin, swelling it in water and from it taking a cast in plaster-of-paris.

Bath

A term applied to various solutions in which plates, papers or films are immersed, and also to the vessel holding such solutions.

Swing Bed

Many of the modern folding cameras have the front portion which forms the bed so adjusted that it is possible to change its position from the horizontal, thus permitting of the lens being pointed upward or downward. The swing-bed takes the place of the swing-back and when a camera is equipped with a swing-bed, usually there is only one swing to the back, which is the side-swing.