Daguerreotype:  the first practical photographic process, invented by Daguerre and described by him in 1839.  The process produced a positive image formed by mercury vapor on a metal place coated with silver iodide.

Daylight film:  color film that is balanced to produce accurate color renditions when the light source illuminating the photographed scene has a color temperature of about 5500K, such as in midday sunlight or with electronic flash or blue flashbulb

Dense describes a negative or an area of a negative in which a large amount of silver has been deposited.  Dense negatives transmit relatively little light. Opposite: thin

Densitometer:  an instrument that measures the darkness or density of a negative or print

Density:  the relative amount of silver present in various areas of film or paper after exposure or development; therefore, the darkness of a photographic print or the light-stopping ability of a negative or transparency

Depth of field:  the area between the nearest and farthest points from the camera that is acceptably sharp in an image

Developer:  a chemical solution that changes the invisible, latent image produced during exposure into a visible one

Diffuse:  scattered, not all coming from the same direction; i.e., sunlight on a cloudy day

DIN:  a numerical rating used in Europe to describe the sensitivity of film to light.  The DIN rating increased by 3 as the sensitivity of the film doubles

Dodge:  to lighten an area of a print by shading it during part of the printing exposure

Dry down:  to become very slightly darker & less contrasty, as most photo printing papers do when dried after processing

Dry mount:  to attach a print to another surface, usually mat board, by placing a sheet of dry-mount adhesive between the print & the mounting surface.  This “sandwich” is placed in a heated mounting press and the adhesive melted.  Pressure sensitive adhesive that doesn’t require heat may also be used.

DX coding a checkered or bar code on some film cassettes for electronic scanning of information by automatic cameras and processing equipment that tells the speed of the film and number of exposures