Capable of being altered by the action of light.


A term used in connection with plates and papers designating the amount of time required for a certain strength of light to impress itself on the emulsion, either visibly or invisibly.


An instrument for testing and comparing the sensitiveness of various photographic emulsions on plates and papers.


A color or tone of print. Some of the various black and white printing processes will give a sepia or brownish-colored image, if the print is developed or toned with a suitable solution. There are some printing processes which will give a sepia or brownish-colored image by means of a single solution; other printing processes require simply washing the print in water in order to get the sepia tone.

Sepia Paper

A paper which will give a sepia-colored image.


A metallic frame or carrier used in magazine cameras for holding dry plates in position.

Shellac. Gum Lac

Reddish-brown, brittle, inflammable substance; thin sheets. Bleached shellac is white opaque, brittle masses. Soluble in alcohol and in water containing borax, sodium carbonate, caustic soda or ammonia. Used principally in varnishes.


An instrument or attachment to regulate the amount of exposure to be given the sensitive plate in the camera. Shutters are of various forms, some fitting in front of the lens, some between the lens, some immediately back of the lens, while others are operated just in front of the sensitive plate. A complete description of the various forms of shutters is given in the text.

Automatic Shutter

A form of shutter working between the cells of a doublet lens or in front of a single lens, setting itself automatically after each exposure.

Behind-the-Lens Shutter

A behind-the-lens shutter is practically any form of shutter placed back of the lens.

Between-the-Lens Shutter

A between-the-lens shutter is practically any form of shutter fitted between the two combinations of a doublet lens or lens cells of any other form of lens.

Cloud Shutter

A specially constructed shutter giving much less exposure to the clouds than the foreground.

Diaphragm Shutter

A shutter working between the cells of a double lens, and also acting as a diaphragm for the lens.

Drop Shutter

A form of shutter for making quick exposures, its principle being; a slide, containing an aperture which admits light to the lens, is set in a frame and allowed to drop in front of the lens.

Focal Plane Shutter

A shutter working at a very slight distance in front of the plate. Theoretically, it should work in identically the same plane as the sensitive plate.

Instantaneous Shutter

A shutter so regulated as to allow of extremely short exposures being made.