Distilled Water

(See Water, Distilled.)

Distortion

A defect which will occur when photographing objects having perpendicular lines, if the camera is tilted upward and the ground-glass is not kept parallel to the subject; also an optical defect consisting of the curving of straight lines, which occurs with a single lens.

Divergent

An optical term denoting the departing or receding of lines from each other.

Dividing the Focus

Doctoring Negatives

(See Negatives, Doctoring.)

Dodging in Printing

As comparatively few negatives are perfect, it is often necessary to hold back certain portions while printing. For example; a hard, contrasty negative with almost opaque highlights and clear shadows can be greatly improved by holding back the printing of the shadows. This is called dodging.

Double Concave

(See Lens Concave, Double.)

Double Convex

(See Lens Convex, Double.)

Double Exposure

(See Exposure, Double.)

Double Extension

(See Extension, Double.)

Double Image

(See Image, Double.)

Double Mounting

(See Mounting, Double.)

Double Plate-Holder

A plate-holder which will hold two plates. (See Plate-Holders.)

Double Printing

(See Combination Printing.)

Doublet Lens

(See Lens, Doublet.)

Drachm or Dram

A small weight, being 1/8 of an ounce in apothecaries' weight, or 1/16 of an ounce in avoirdupois weight; also 1/8 of an ounce fluid measure.

Dragon's Blood

A resin so named because of its red color. Very opaque and brittle, tasteless and without odor. Dissolves in alcohol or ether. Used in the preparation of varnishes.

Drain Rack

Rack made of wood on which to drain dry plates; also racks placed in sinks on which to rest trays, etc.

Drawing Paper

A special, tough paper, obtainable at stationery stores. Often used as a base for the Kallitype and other home-sensitizing processes.

Dropping Bottle

(See Bottle, Dropping.)

Drop Shutter

(See Shutters, Drop.)

Dry Distillation

(See Distillation, Destructive.)

Dry Mounting

(See Mounting, Dry.)

Dry Mounting Tissue

(See Mounting Tissue, Dry.)

Dry Plates

Plates of glass coated with an emulsion composed of gelatin and sensitive silver salts.

Drying Negatives

(See Negatives, Drying.)

Dynar Lens

(See Lens, Dynar.)

Eau de Javelle

A reducing solution composed of chloride of lime and potassium carbonate. Used for eliminating sodium hyposulphite from negatives or prints after fixing. It is also a stain remover and a reducer. It may be prepared as follows:

Potassium Carbonate.......................................

2 ozs.

Chloride of Lime (dry)....................................

1 oz.

Water ................................

20 ozs.

Mix the chloride of lime with 15 ounces of water and dissolve the potassium carbonate with the remainder. Then mix the two solutions. Boil and afterwards filter. When cool it is ready for use.