Color Screen

(See Color Filter.)

Prismatic Colors

(See Prismatic Colors.)


A defect in a lens caused by incomplete correction of the spherical aberration of oblique rays. It is a pear-shaped or comma-shaped blurr of light partly surrounding the image and a bright light.

Combination Printing

An operation requiring two or more negatives, from which the whole or portions are printed for securing the best of composition and the most pleasing effect in a picture.

Combined Toning Bath

(See Toning Bath, Combined.)


Chemical action producing the sensation of heat and sometimes light.

Comparative Exposure

(See Exposure, Comparative.)

Composite Photograph

Composite.) Composition (See Photograph

An art term which designates the difference between a good and a bad picture and constitutes the general arrangement of lines, lights, shades and masses.

Concave Lens

(See Lens, Concave.)

Double Concave

(See Lens, Concave, Double.)

Piano Concave

(See Lens, Concave, Piano.)

Concavo-Convex Lens

(See Lens, Concavo-Convex.)

Concentrated Solutions

(See Solutions, Concentrated.)


A lens used to collect the rays of light, concentrating them upon one point. Used in enlarging, and lantern-slide, lanterns.


(a) An optical term used to denote a pencil of rays of light which emanate from a point and diverge as they proceed on their course, (b) An attachment made of paper or tin (blackened) placed on the front of the lens to prevent the objectionable rays of light from entering the lens.

Conjugate Foci

(See Foci, Conjugate.)

Construction Work

Optical Contact

(See Optical Contact.)

Contact Printing

(See Printing, Contact.)

Continued Action of Light

(See Light, Continued Action of.)


The degree of difference between high-lights and shadows. (See Chalkiness.)


An optical term applied to rays of light which, if continued, will meet in a focus.

Convergent Lens

(See Lens, Convergent.)

Convertible Lens

(See Lens, Convertible.)

Convex Lens

(See Lens, Convex.)


(See Lens, Convexo-Concave.)


(See Lens, Convex, Double.)


(See Lens, Convexo-Plano.)

Cooke Lens

(See Lens, Cooke.)


Gum Copal; Resin Copal.

Yellowish to yellowish-brown pieces of various sizes. Glossy, odorless and tasteless. Soluble in alcohol, ether, turpentine and linseed oil, after having been fused. Used as a substitute for amber, also in varnishes and cements.



Granulated, sheet and filings. Reddish in color, ductile, malleable, hard metal. Used to precipitate the silver from old fixing baths.