A single-lens reflex camera that uses a digital sensor rather than film.

The process of changing a series of representative digitized values into continuously varying analogue data.

Dark current noise is caused by the accumulation of stray electrons in sensor pixels not exposed to light. It reveals itself as random noise in shadow or dark areas of images. The phenomenon is cumulative over time and so becomes more noticeable when exposure periods are very long.

An assessment of the clarity of an image, or of the amount of detail which can be perceived within it.

The range of distances from a lens within which an object is considered acceptably sharp.

The range of distances, measured along the optical axis, through which the image of an object (on the film or sensor side of a lens) may be moved whilst retaining acceptable sharpness (as defined by the diameter of the acceptable circle of blur).

A control that shuts lens aperture down to a pre-selected level and makes depth of field visible through the viewfinder.

A set of crescent-shaped blades forming a near-circular hole at the centre of the lens, and used to control the amount of light reaching a film or sensor. The diameter of the hole varies as the blades slide over each other under the control of an external ring. The aperture can typically be varied from a tiny opening a few millimetres in diameter to the maximum diameter of the lens.

Control of shallow depth of field envelope to focus sharply upon a particular part of an image, allowing other areas to drop out of focus.

This is an open format file format similar to a RAW file that is consequently independent of manufacturer-specific software. Digital negatives require processing before they can be viewed or processed, but are capable of delivering more colour and dynamic range than TIFF or JPEG files.

Dispersion is a phenomena which separates spatially the various wavelengths (colours) of which white light is comprised. A dispersive material has a different refractive index for each wavelength of light, and consequently refracts (deflects) each wavelength by a different angle. The simplest demonstration of dispersion is the rainbow of colours produced by passing a ray of white light through a prism.

A darkroom or equivalent digital technique for decreasing local contrast and density in an image.

To transfer computer files to a more local or less significant location ie from a personal computer to a CD.

A unit used to measure the resolution of an image produced by an output device such as a printer. The greater the number of dots per inch the higher the resolution of the image.

A mode of printing an image using two colours.

Digital versatile disk; similar to a CD but offering larger storage capacity.

A system that reads bar codes on film cassettes and uses the information to set ISO rating automatically.

The range of energy levels that can be captured by a recording or reproduction device. A good digital camera might manage 10 stops and a film scanner perhaps 8 stops.