A Glossary of Photographic Terms: D

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Some of the ready resources: Nikon - Terms, SLRs, lenses || Canon - A & T series SLRs , FD Lenses || Minolta -XK/XD11 || Pentax - LX || Olympus - OM1/OM2 series, Zuiko Lenses || Contax - RTS Series | Hasselblad - Bodies, older lenses | Rollei - bodies

D-type AF Nikkor lenses (Only apply to Nikon):

AF Nikkor lenses that send Distance Information to some of Nikon's top cameras, Used for 3D Color Matrix Metering or 3D Multi Sensor Balanced Fill Flash (with Nikon SB 27/SB 26/SB 25 Speedlight). Some third party lens manufacturers are catching up to supply with compatible functions lenses too.

DC (Defocus Image control)

A new type of lens family introduced by Nikon, designated as DC lens. Mainly for portrait photography. The lens enables to control background and foreground blur precisely, resulting in strikingly attractive portraits.


A light tight area used for processing films and for printing and processing papers; also for loading and unloading film holders and some cameras. For image purist, the cycle of photograph is not complete if the darkroom process is not handled personally.

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. A simple glance can differentiate by identifying the multiple contacts on the hot shoe (the place where the flash is mounted).


The clarity of detail in a photograph.

Delayed action.

Mechanism delaying the opening of the shutter for some seconds after the release has been operated. Also known as self-timer.


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


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 zone of acceptable sharpness in front of and behind the subject on which the lens is focused; extends approx. one-third in front of and two thirds behind the in-focus subject; dependent on three factors: aperture, focal length, and focused distance; the wider the aperture, the longer the focal length, and the closer the focused distance, the less the depth of field, and vice versa; in comparison to a normal lens, wideangle lenses have inherently more depth of field at each f-number and telephoto lenses have less.

Since this element is very important, another simpler way to explain is 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 or can explain as in simpler term as the zone of sharpest focus in front of, behind, and around the subject on which the lens is focused; can be previewed in the camera - very handy for critical work. Relating article in this site: Depth of field.

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. Also see "depth of field" section.


A solution used to make visible the image produced by allowing light to fall on the light-sensitive material. The basic constituent is a developing agent which reduces the light-struck silver halide to metallic silver. Colour developers include chemicals which produce coloured dyes coincidentally with reduction of the silver halides.

Developing Tank

A light tight container used for processing film, a darkroom's essential accessory.


An adjustable device inside the lens which is similar to the iris in the human eye; comprised of six or seven overlapping metal blades; continuously adjustable from "wide open" to "stopped down"; controls the amount of light allowed to pass through the lens and expose the film when a picture is taken; a]so controls the amount of depth of field the photograph will have; in lenses designed for single-lens reflex cameras, there are basically two types of diaphragms: 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. The more blades used will have a more natural and rounded spots.

There are two types of diaphragms:

Automatic: The most popular type; controlled by a single aperture ring; during viewing and focusing, the diaphragm remains wide open, allowing the maximum amount of light to go to the viewfinder for a bright and easy-to-focus image; at the instant of exposure, it stops down automatically to a particular aperture and then reopens to full aperture immediately afterward.

Manual Preset: Used in some specific lenses like, PC-Nikkor lenses for Nikon for instance; controlled by two separate rings; the preset ring is first set to the desired aperture, then the aperture ring is rotated to stop down the diaphragm manually for metering or prior to taking pictures.

Diffuse Lighting

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


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 minimised.


Deutche Industrie Norm (Film speed rating defined by the Deutscher Normenausschuss (German standards organisation).). Numeric rating used to describe emulsion speed for German Made photosensitive materials. Just as the same as ASA and ISO numbers.


The property of materials which have a refractive index that varies according to the wavelength of light, i.e., bend the rays of some colors more than others; a prism placed in the path of a ray of white light bends the blue and violet rays more than the orange and red, so that it spreads out or "disperses" the colors as a continuous spectrum.


Even if the other possible aberrations were totally eliminated, images could result that still have a distorted appearance. For an example, an rectangle may appear as a barrel or pin cushion-shaped object. A lens aberration which does not affect the sharpness of the image, but alters the shape of objects; the inability of a lens to render straight lines perfectly straight; does not improve by stopping down the lens; there are two types of distortion:

Barrel: Straight lines are bowed in at the edges of the picture frame re sembling the sides of a barrel; pres ent in small amounts in some wideangle or wideangle-zoom lenses, bu~ uncorrected in fisheye lenses.

Pincushion: The opposite of barrel distortion; straight lines are bowed in toward the middle to resemble the sides of a pincushion; present in smal amounts in some telephoto and telephoto-zoom lenses.


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. Some cameras can have double exposure level depressed with multiple exposures one even with a motor drive.

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.


Digital Index. Coding on the film cartridges used to transmit information in relation to film speed, the length of film and the exposure latitude to the camera. Most films - except some technical films are DX coded - means you need not to worry about wrong setting of the ISO setting of film speed anymore, reducing chances of mistakes. Common speed ISO 25 to 6400 - depends on camera models.

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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