A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Daguerre, Louis Jacques Mandé, 1789-1851 - French painter who, in 1839, with Nicéphone Niépce, invented the daguerrotype.

Daguerrotype - (1) An obsolete photographic process in which a picture made on a silver surface sensitized with iodine was developed by exposure to mercury vapor. (2) A picture made by this process.

Darkcloth - Material used to cover the photographer’s head and camera to block surrounding light in order to better view the image on the camera’s ground glass viewing screen.

Darkroom - A room in which total darkness is achievable, permitting light-sensitive materials such as film to be handled without fear of their exposure to light.

Darkslide - An opaque sheet that is slid in place over the front of a sheet film holder to protect the film from exposure to light.

Daylight film - Film balanced to give accurate colors when exposed to a subject lit by daylight or light of similar color-temperature- for example, electronic flash. Dedicated flash

Dedicated Flash - A flash unit made for a specific make of camera or range of makes, that uses the camera's TTL metering system to control light output automatically.

Definition - Sharpness of an image (as seen by the clarity of detail) formed by an optical system.

Densitometer - Instrument that measures optical density of part of a negative or print.

Density - The relative opacity (blackness) of an area of a negative, a transparency or a print. The greater the density, the less light can be transmitted through it. (Sometimes density is also referred to as "Contrast.")

Depth of field - The zone of acceptable sharpness in a picture, extending in front of and behind the plane of the subject, that is most precisely focused by the lens. You can control or exploit depth of field by varying three factors: the size of the aperture: the distance of the camera from the subject and the focal length of the lens. If you decrease the size of the aperture, the depth of field increases; if you focus on a distant subject, depth of field will be greater than if you focus on a near subject; and if you fit a wide-angle lens to your camera, it will give you greater depth of field than a normal lens viewing the same scene. Many SLRs have a depth of field preview control - a button that closes the lens diaphragm to the aperture selected for an exposure so that the depth of field in the image can be checked on the viewing screen first.

Depth of field preview button - Many cameras are equipped with a preview button that, when pressed and held in, stops the lens down to the preselected aperture, allowing you to see how much foreground or background are in focus.

Depth of field scale - Markings on the barrel of a lens that show the depth of field for a particular aperture and a particular focus setting.

Depth of focus  - A zone of focus in the camera. If an image is focused on a ground glass screen in a camera, depth of focus makes it possible to move the screen slightly backward or forward and still have the image in acceptable focus.

Developer - A solution containing a number of chemicals that will convert a latent image on an exposed photographic material to a visible image.

Developing tank - A light-tight container, made of plastic or steel, in which film is developed. The exposed film is loaded into the tank in complete darkness, and temperature-controlled chemicals are added at pre­cisely timed intervals to make the image visible and stable.

Diaphragm - The part of the camera that governs the size of the aperture. The most common type is the iris diaphragm - a system of curved, overlapping metal blades that form a roughly circular opening similar to the iris of the eye. It varies in size to control the amount of light.

Diffraction - A phenomenon exhibited by a light’s wave front when passing the edge of an opaque object (one that does not allow light to pass through it). The light becomes modulated, causing a redistribution of the light’s energy within the wave front. You will see it at the edges of the object’s shadow, in the form of minute dark and light bands. The edges of the shadow have a fuzzy appearance. Think of ripples meeting a rock in a pond. They go around the rock in a new series of ripples that can be seen on the sides of the rock. Light waves behaving in a similar manner are said to be diffracted.

Diffraction filter - A colorless filter inscribed with a network of parallel grooves. These break white light up into its component colors, giving a prism-like effect to highlights.

Diffused light - Light that has Post some if its intensity by being reflected or by passing through a translucent material. Diffusion softens light, eliminating both glare and harsh shadows, and thus can be of great value in photography, notably in portraiture.

Diffuser - Material that diffuses light. A diffuser may be a translucent material or a rough-surfaced reflective material, both of which scatter light’s rays, thereby softening the light.

Diffusion-condenser enlarger  - An enlarger that has both a condenser system (for greater contrast) and a diffused light, producing less contrast than a condenser enlarger but more contrast and sharper detail than a diffusion enlarger.

Diffusion enlarger - An enlarger in which the light is diffused, and therefore spread more evenly as it strikes and passes through the negative, resulting in less sharpness of detail. Negative flaws (scratches, etc.) are de-emphasized with a diffusion enlarger.

Digital camera- A camera that takes pictures without film, but instead records the image on an image sensor chip in a format that is readable by a computer.

Digital capture - In photographic context, all electronic (non-film) registration of pictures.

DIN see FILM SPEED Dodging (shading) - German standards system that expressed a film speed rating by a number followed by a degrees sign ( ° ). DIN derives its name from the initials of the Deutsche Industrie Normen or Deutsche Industries Norm. The DIN system has been replaced by the more universal ISO system.

Diopter - A unit of measure of the refractive power of a lens.

Distortion - Misrepresentation of proportions of objects or of their arrangement in a scene. The two main types of lens distortion are: (1) Barrel distortion, in which the straight lines near the edges of the viewframe appear bowed outward from the centre, like a barrel-shape; and (2) Pincushion distortion in which the same lines bend in towards the centre.

Dodging - Blocking a portion of the light when printing a photograph so that an area of the print will be made lighter.

Drop-in loading  - Camera system that automatically advances film to the first frame when the camera's back is closed.

Double exposure - The recording of two images on the same frame of film. When more than two images are recorded, the term "multiple exposure is used.

Dry mounting  - A means of attaching a print to a backing using a thin paper stock coated on each side with a dry cement that melts under heat.

DX - A coding system using a pattern of squares printed on a film cassette that can be read by a DX-enabled camera to automatically set film speed for the camera’s exposure meter, to set the number of frames and other data. Also called "DX coding" or "DX encoding."

DRY MOUNTING - A means of attaching a print to a backing using a thin paper stock coated on each side with a dry cement that melts under heat.

DX - A coding system using a pattern of squares printed on a film cassette that can be read by a DX-enabled camera to automatically set film speed for the camera’s exposure meter, to set the number of frames and other data. Also called "DX coding" or "DX encoding."