A Glossary of Photographic Terms: D

Darkroom

A lighttight area used for processing films and for printing and processing papers; also for loading and unloading film holders and some cameras.

Data Disk

A circular, rotating disk at the end of Advanced Photo System film cassettes that functions as a circular bar code, communicating the film speed, type and exposure length through a sequence of reflective bars to an optical sensor in the camera.

Dedicated Flash

A fully automatic flash that works only with specific cameras. Dedicated flash units automatically set the proper flash sync speed and lens aperture, and electronic sensors within the camera automatically control exposure by regulating the amount of light from the flash.

Definition

The clarity of detail in a photograph.

Densitometer

An instrument used for measuring the optical density of an area in a negative or print.

Density

The blackness of an area in a negative or print that determines the amount of light that will pass through it or reflect from it. Sometimes referred to as contrast.

Depth of Field

The amount of distance between the nearest and farthest objects that appear in acceptably sharp focus in a photograph. Depth of field depends on the lens opening, the focal length of the lens, and the distance from the lens to the subject.

Photographer: Iliana Cornejo KINSA/KODAK Photo Contest Film: KODAK EKTAPRESS 1600 Film Size: 35 mm

Depth of Focus

The distance range over which the film could be shifted at the film plane inside the camera and still have the subject appear in sharp focus; often misused to mean depth of field.

Developer

A solution used to turn the latent image into a visible image on exposed films or photographic papers.

Developing Tank

A lighttight container used for processing film.

Diaphragm

Lens opening. A perforated plate or adjustable opening mounted behind or between the elements of a lens used to control the amount of light that reaches the film. Openings are usually calibrated in f-numbers.

Diffuse Lighting

Lighting that is low or moderate in contrast, such as on an overcast day.

Diffusing

Softening detail in a print with a diffusion disk or other material that scatters light.

Diffusion-Condenser Enlarger

An enlarger that combines diffuse light with a condenser system, producing more contrast and sharper detail than a diffusion enlarger but less contrast and blemish emphasis than a condenser enlarger.

Diffusion Enlarger

An enlarger that scatters light before it strikes the negative, distributing light evenly on the negative. Detail is not as sharp as with a condenser enlarger; negative blemishes are minimized.

Dodging

Holding back the image-forming light from a part of the image projected on an enlarger easel during part of the basic exposure time to make that area of the print lighter.

Double Exposure

Two pictures taken on one frame of film, or two images printed on one piece of photographic paper.

Photographer: Paul Michael Leeder KINSA/KODAK Photo Contest Film: KODAK EKTAR 100 Film Size: 35 mm

Drop-in-Loading (DIL)

Film cassette loading feature in all Advanced Photo System cameras that virtually eliminates film-loading problems by automatically accepting the leaderless cassette and thrusting the film forward to the first unexposed frame without any user intervention.

Dropouts

Those black or white streaks, spots, and comets zipping across the screen. We count as dropouts any loss of playback signal that is 20 decibels or more below the nominal playback level (16 decibels for extra high-grade and 8mm tapes) and lasting for 15 microseconds or longer (about one quarter of one horizontal scan on the TV screen).

DX Data Exchange

Electrical coding system employed in 35 mm format film that communicates film speed, type and exposure length to the camera.

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