A flexible cable used to release a camera shutter without causing movement and consequent blurring of an image. It is normally used in conjunction with a tripod and a slow shutter speed.
RAM used to hold computer data recently read from a mass storage device. Its purpose is to speed up processing.
The size and aspect ratio of an image produced on film or a digital sensor by a camera body. The format is determined by the physical dimensions of the focal plane or image sensor.
Movement of a camera during the exposure period, perhaps causing loss of detail or blurring.
The camera obscura consists of a darkened room with a small aperture opened in one wall. An inverted image of the scene outside the room is projected through the aperture and onto the opposite (usually white) wall. Eventually a converging lens was fitted in to the aperture to produce clearer and sharper images.
The quantity of computer data that can be held by a storage device, usually quoted in MB or GB or TB.
A long focal length lens using mirrors within its construction. The mirrors allow a long focal length to be achieved within a comparatively short lens barrel. This type of lens is also known as a mirror or reflex lens.
Small specular reflections of a light source usually seen in the eyes in portraiture. Lack of catch lights in portraits may be regarded as a deficiency.
Silicon chip used as an electronic sensor to replace film in a digital camera. It has electrodes arranged in a rectangular array. The electrodes a light sensitive and correspond to pixels. The light level measured by each electrode is turned into a digital code.
Exposure determination system commonly found in SLRs and DSLRs giving greater emphasis to brightness in the centre of the field of view.
A light-proof black fabric bag used to handle film and other light-sensitive materials in daylight. Most have two separate layers equipped with zips, and a pair of sleeves with elastic armholes.
The purity of a colour measured as a product of hue and brightness, or the degree of departure of a colour from the neutral. Colours having a low chroma value are usually described as weak, whereas those with a high chroma are said to be strong or highly saturated.
B&W films that can be processed using standard C-41 colour chemistry to produce monochrome prints.
The diameter of a spot that cannot be distinguished from a point in an image at a normal viewing distance of 250mm. This measurement is an essential element in calculating depth of field.
An adjustment made in a photographic process to ensure that neutral greys in a subject remain neutral in an image.
A false predominance or bias of a particular colour spread evenly throughout an image, and usually most apparent in light neutral tones.
The process of controlling the colours in an image reproduction system such that they are repeatable and acceptably accurate. Key components of colour management are monitor and printer calibration.
A quantitative measure of the ability of a light source to reproduce colours - measured against their perceived appearance in natural light or under a reference illuminant. natural sunlight is considered to have a CRI of 100.
Measure of the colour of a light source in terms of physical temperature (degrees Kelvin) of a black body radiator. Daylight approximates to 5,400oK and a sunset to 2,800oK.
The inability of a lens to render off-axis point sources of light as circular. Points appear as comet-shaped blurs, from which the name coma is derived, with the tails flaring toward the centre of an image. The problem is minimized by closing down the lens diaphragm.The aberration is difficult to eliminate in wide-angle lenses with large maximum apertures.
A memory card designed to store images within a digital camera. Many digital cameras with PC card interfaces use this storage technology which conforms to a standard supported by the CompactFlash Association. CompactFlash is ATA compatible and the cards fit Type II or Type III slots when used with a passive adapter.
Pairs of colours of light which, when combined in equal proportions, produce white light - ie cyan and red, yellow and blue.
The process of encoding digital files in a space-efficient manner. Compression algorithms remove unnecessary information from files in a way that allows it later to be replaced. No compression of physical storage is involved.
A same-size print of all the negatives on a roll of film used to select images for enlargement.
The brightness range in a scene, or the difference in brightness between adjacent areas of tone. Also, the rate at which processed film density increases with greater exposure.
The appearance of parallel lines in a view, as seen in an image, when photographed from an angle.
An electronic component that controls the principal functions of a computer or camera. Automatic cameras have at least one CPU to control essential functions. More sophisticated models may have numerous CPUs to handle exposure, autofocus etc. Some autofocus lenses also have built-in CPUs to communicate information such as focal length, focus distance, and lens type to the body of the camera.
To use or remove part of an image typically to improve composition or make it fit a given space.
A sensor in a digital camera having dimensions smaller than those of the comparable film-based format.