Photography glossary - A

Abbe number - denotes the degree of refraction of light of different wavelengths to different extents, given by a transparent material, such as glass. The lower the Abbe number, the greater the dispersion of colors.

Aberration - the inability of a lens to produce a perfect, sharp image, especially towards the edge of the lens field. These faults can be reduced by compound lens constructions, and the use of small apertures.

Abrasion marks - marks on the emulsion surface of a film, caused by scratching. It can be due to traces of dirt trapped between layers of film as it is wound on the spool, or to grit on the pressure plate. read more in color pipeline

Absolute released images - any images for which signed model or property releases are on file and immediately available.

Absolute temperature - the temperature at which most molecular movement ceases. It is often referred to as absolute zero (-273° C).

Absorption - the process by which light falling on a surface is partially absorbed by the surface.

Abstract - subjective, non-realistic image. An abstraction photograph generally contains a design of patterns or shapes where the identity of a subject is not evident.

AC adapter Mains adapter. Enables the connection of the digital camera to the mains electricity supply.

Accelerator - chemical added to a developing solution to speed up the slow working action of the reducing agents in the solution.

Acceptance (payment on) The buyer pays for certain rights to publish a picture at the time it is accepted, prior to its publication.

Acceptable Circle of Confusion - the size of the largest circle which the eye cannot distinguish from a dot. In 35mm format cameras, a 0.03mm diameter circle of confusion is considered acceptable. It is used to calculate depth-of-field or depth of focus.

Accessory shoe - metal or plastic fitting on the top of the camera which supports accessories such as viewfinder, rangefinder, or flash gun.

Acetate base- non-inflammable base support for film emulsions which replaced the highly inflammable cellulose nitrate base.

Acetic acid - chemical used for stop baths and to acidify acid fixing solution.

Acetone - solvent chemical used in certain processing solutions that contain materials not normally soluble in water.

Achromatic - lens system that has been corrected for chromatic aberration.

Acid - chemical substance with a pH value below 7.

Acid fixing solutions - solutions which contain an acid to neutralize any carry-over of alkaline developer on the negative or print.

Acid hardener - substance used in acid fixer to help harden the gelatin of the emulsion.

Acid rinse - weak acid solution used after development and before fixation. By neutralizing alkaline developer left on the photographic material it arrests development. •Actinic - the ability of light to cause a chemical or physical change in a substance.

Actinometer - early type of exposure calculator.

Acuity - subjective term for the visual sharpness of an image.

Acutance - objective measurement of image sharpness. Refers to how noticeable the transition is from one luminosity to another across an edge.

Adapter ring - circular mount, available in several sizes, enabling accessories such as filters to be used with lenses of different diameters.

AD conversion - Analog-Digital conversion. In order to process an analog signal(e.g. a photo) in a computer, it must first be digitised (converted into a specific mathematical format of binary code). Pictures are usually digitised with the help of a digital camera or a scanner.

ADC - Analog-Digital Converter. Hardware that converts analog information into digital data.

A/D Converter (Analog to Digital) A device that converts analog information (a photograph or video frame) into a series of numbers that a computer can store and manipulate.

Add-on / Add-in Extension to a program such as Excel or Word that increases the available functions. These add-ons/add-ins are developed and distributed by the respective software company or other firms.

Additive colour mixing - Describes a colour system that is based upon the addition of the three additive primary colours (red, green, and blue). For example, colour televisions and computer monitor displays use the principle of additive colour mixing.

Additive color - see Additive Printing.

Additive printing - color printing method which produces an image by giving three separate exposures, each filtered to one of the three primary color wavelengths, blue, green and red.

Additive synthesis - method of producing full-color images by mixing light of the three primary color wavelengths, blue, green and red.

Adobe RGB (1998) color space developed by Adobe

Aerial perspective - the distance or depth effect caused by atmospheric haze. Haze creates a large amount of extraneous ultra-violet light to which all photographic emulsions are sensitive.

Aerial Photography Photographs taken from airplane or other means to produc high altitude Photography

AE - Automatic exposure.

AF lock - stops autofocus operation once the subject is in focus. Useful when shooting a subject outside the focus area in the viewfinder. The photographer should first lock the focus with the subject inside the focus area, then recompose the shot as neccesary.

A focal lens - lens attachment that alters the focal length of the camera lens without disturbing the distance between the lens and the film plane.

AF Sensor - the sensor used to detect focus.

Aftertreatment - the treatment of negatives and prints to correct certain faults in exposure and development, or to create special effects.

Agitation - method by which fresh solution is brought into contact with the surface of sensitive materials during photographic processing.

Agency promotion rights. Request by stock agencies to reproduce images in promotional material.

Agent. Person who represents the photographer and his images on his behalf.

Air bells - bubbles of air clinging to the emulsion surface during processing.

Air brushing - method of retouching b&w or color photographs where dye is sprayed, under pressure, on to selected areas of the negative or print.

Air-to-air photography - photography of aircraft in flight from another aircraft.

Aliasing - Pixel-shaped curves on the diagonal edges of objects. This can sometimes occur since all graphics consist of individual pixels. Anti-aliasing reduces this unwelcome effect by recalculating the contrast values of the neighbouring pixels and matching them up with each other.

Altavista - Well-known search engine in the internet.

Albert effect - effect that creates a reversed image. An exposed frame of film, treated with dilute chromic acid is exposed to light. Development then gives a positive image by darkening the film grains that were not initially affected by exposure.

Albumen paper - printing paper invented by Blanquart-Evrard in the mid-19th century where egg whites were used to coat the paper base prior to sensitization. The albumen added to the brightness of the white base and substantially improved printed highlights.

Alcohol thermometer - instrument used for measuring temperature. It is an inexpensive and less accurate version of the mercury thermometer.

Algorithm - A set of processing or working instructions that, because of their high precision, can be carried out independently by a mechanical or electronic device. Algorithms are, for example, the set rules for addition and subtraction etc. However, they are also the instructions that are established in a programming language. Algorithms simply allow the computer to solve particular problems. In image editing, algorithms are used to alter images, e.g. 3 D Cubic Algorithm.

Alkalinity - denotes the degree of alkali in a solution, measured in pH values. All values above pH 7 are alkaline. Allegory - work of art that treats one subject in the guise of another. An allegoric photograph usually illustrates a subject that embodies a moral "inner meaning".

Alum - chemical used in acid hardening fixing baths.

Aluminum compounds - groups of chemicals often used as hardeners in fixing baths.

Alternative process. Word used for old recipes of photography methods that do not depend on silver based imagery. Cyanotype, Palladium-, Platinum- and salted paper print.

Ambient light - the available light surrounding a subject. Light already existing in an indoor or outdoor setting that is not caused by any illumination supplied by the photographer.

Ambrotype - Mid-19th century photographic process introduced in 1851-52 by Frederick Scott Archer and Peter Fry. It used weak collodion negatives which were bleached and backed by a black background which produced the effect of a positive image.

Amidol - soluble reducing agent which works at low pH values.

Ammonium chloride - chemical used in toners and bleachers.

Ammonium persulfate - chemical used in super-proportional reducers.

Ammonium sulfide - pungent but essential chemical in sulfide or sepia toning.

Ammonium thiosulfate - highly active fixing agent used in rapid fixing solutions which works by converting unused silver halides to soluble complexes.

Amphitype - Mid-19th Century process based on an underexposed albumen-on-glass negative. This was viewed by reflected light against a black background to give a positive image similar to a ambrotype.

Analog - Opposite of digital. Analog data merges continuously into each other without clearly defined steps (e.g. the colours of a rainbow are not obviously separable from one another).

Anaglyph - result of forming stereoscopic pairs from two positives each dyed a different color, usually green or red.

Analyzer - chart, grid or electronic instrument used to determine correct color filtration when making color prints.

Anamorphic lens - lens capable of compressing a wide angle of view into a standard frame.

Anastigmat - compound lens which has been corrected for the lens aberration "astigmatism".

Angle of incidence - when light strikes a surface it forms an angle with an imaginary line known as the :normal," which is perpendicular to the surface. The angle created between the incident ray and the normal is referred to as the angle of incidence.

Angle of view - is the maximum angle of acceptance of a lens which is capable of producing an image of usable quality on the film.

Angstrom - unit of measurement used to indicate specific points of wavelengths within the electromagnetic spectrum. Visible light rays occur between 4000 - 7000 Ã….

Angular field- the angle subtended at the lens by the diameter of the largest circle within which the lens gives an image of acceptable sharpness and even illumination.

Anhydrous - dehydrated form of chemical. More concentrated, so that less weight is needed in a formula than the crystalline kind.

ANSI - speed rating system for photographic materials devised by the American National Standards Institute.

Anti-aliasing The process of reducing stair-stepping by smoothing edges where individual pixels are visible.

Anti-fogging agent - constituent of a developer that inhibits or reduces fogging during development.

Antihalation backing - dye used on the back of most films capable of absorbing light which passes straight through the emulsion. In this way it reduces the amount of extraneous light that can be reflected from the camera back through the emulsion.

Antinous release - alternate term for a camera cable release.

Antiscreen plates - photographic plates containing dyes that reduce the blue sensitivity. Used unfiltered, they can give results similar to those obtained with yellow filtered orthochromatic plates.

A-PEN - annealed polyethylene naphthalate. A polyester material used as the base on Advanced Photo System film.

APS - Advanced Photo System. Developed together by five companies, this film system is distinguished by simple operation, a new picture format (16 x 30 mm) as well as a choice of three picture formats. Additional information (such as exposure, aperture and date) can be recorded on the magnetic strip of the APS film.

Aperture - Mechanism behind/in front or in the lens that controls the amount of light entering the camera and falls on to the film plane/censor. The aperture not only influences picture brightness but also regulates focus depth. Most cameras are equipped with an iris aperture that can be freely adjusted or set according to pre-selected values.

Aperture software - Software developed by Apple Computers for cataloging and working with digital images

Aperture priority camera - semi-automatic camera on which the photographer sets the aperture and the camera automatically sets the shutter speed.

Aperture ring - ring located on the outside of the lens usually behind the focusing ring, which is linked mechanically to the diaphragm to control the size of the aperture.

AppleTalk - A network protocol used by Macintosh computers.

Aplanat - lens which has been corrected for spherical aberration.

Application â A computer program, such as an image editor or image browser.

Apochromat - lens corrected for chromatic aberration in all three primary colors.

APO (Apochromatic) - the ability to bring all colors of the visible spectrum to a common plane of focus, within close tolerances. It usually refers to a lens with such superior color correction.

Apodization - lens treatment designed to cut down diffraction fringes that appear around the images bright points of light.

APS (Advanced Photo System) - consumer photography developed by Kodak and four other companies - Canon, Fuji, Minolta and Nikon . It is based on a new film format and photofinishing technologies.

Aqua Case - Waterproof plastic casing for digital cameras.

Aquatint - etching technique allowing control of tonal areas to produce almost unlimited gradations from pale gray to black. Because of this it has also been used in photography as an alternative term for gum bichromate process.

Arhival - Storage of material in a non harmful way that prevents them from fading.

Archival permanence treatments - various treatments given to prints to make them fade-resistant.

Artist statement. Short essay describing a photographers mission and creative process.

Arc lamp - photographic lamp in which light is produced by passing an electric current through two carbon rods.

Argentotype - Mid-19th century silver print process, on which the kallitype and sepia paper processes are based.

Aristotype - early commercial print type made on collodion- chloride or gelatin-chloride paper.

Artifact(ing) Distortions or excess noise which are caused by the sensor, the optical system or image processing (such as compression).

Artificial daylight - artificial light having a similar color temperature to daylight. (5000K - 5500K)

Artificial light - all light not originating from a natural source - normally the sun.

Artificial light film - color film balanced for use in tungsten situation usually around 3400k

Assignment. Request from a client to Photographer to with take on the job of making pictures.

Assignment of copyrights, rights. Transfer of the photographers copy right over to a an other party in written contract.

ASA - original system of rating photographic materials, which was devised by the American standards Association. The ISO rating system is now used in place of the ASA.

ASCII - American Standard Code for Information Interchange. The commonly used binary code for a total of 128 symbols (letters, numbers, punctuation and special symbols, how ever, not for umlauts) enables the correct data transfer between software and hardware. The ASCII-code employs the first seven bits of a byte. The first 32 symbols are used as control symbols, e.g. to control a printer.

Aspect ratio - ratio of width to height in photographic prints. The ratio is 2:3 in 35 mm pictures which produces photographs most commonly measuring 3.5 x 5 inches or 4 x 6 inches.

Aspect Ratio (digital)The ratio between the width and height of an image or image sensor.

Aspherical lens - lens with a curved, non-spherical surface. Used to reduce aberrations and enable a more compact lens size.

Aspherical surface - lens surface with more than one radius of curvature, i.e. the surface does not form part of a sphere.

Assembly printing - method of printing using image separations. Yellow, magenta, and cyan films are stacked to make a final, full color print.

Astigmatism - lens aberration making a single point light source impossible to focus as a true point.

ATA - term used to describe a camera, which supports the electrical interface standard, defined by the PC Card Association (formerly PCMCIA), known as ATA (AT Attachment). This is the mobile computing equivalent of the IDE standard for desktop computers.

ATA-Flash- Cards Space-saving integrated plugin memory cards.

Attachment A file sent along with an e-mail message so that it can be viewed or saved by the recipient.

Atmospheric perspective - alternative term for aerial perspective.

Audiovisual - materials such as filmstrips, motion pictures and overhead transparencies which use audio backup for visual material.

Autochrome - early commercial color photography process in which the principles of additive color synthesis were applied.

Autofocus - device used in certain cameras, projectors and enlargers that focuses the image automatically. There are basically two main AF methods in digital camera: the focus detecting method, or passive auto focus usually employs a CCD and works by evaluating the amount of con- trast or the phase difference in a scene. Distance metering or active autofocus utilises an (infrared) light emitter and receiver in a triangular surveying system. Alternatively, the camera uses ultrasound (sonar) and measures the time taken for the sound signal to return. This data is converted by a microprocessor into information about distance and thereby enables the automatic focusing of the lens.

Automatic aperture - lens aperture mechanism that stops down to s preset size just as the shutter is fired, afterwards returning to the maximum aperture again for focusing and composing the next image.

Automatic exposure control - system of exposure setting in a camera, in which the electric current produced or inhibited by the action of light on a photoelectric cell operates a mechanism that adjusts the aperture and/or the shutter speed automatically.

Automatic Flash A flash unit with a light-sensitive cell that determines the length of the flash for proper exposure by measuring the light reflected back from the subject.

Automatic iris - lens diaphragm which is controlled by a mechanism in the camera body coupled to the shutter release.

Automatic lens - lens which remains at full aperture whatever working aperture is set, until the shutter is released. This allows optimum focusing, without affecting metering. Also referred to as Automatic aperture.

Automatic renewal clause. Used in contracts between Potographr and stock agency and usually is in connection with the photographer delivering images and by thus automatically extending the life of the original contract between both party to ceartain amount of time or years.

Autowinder - film wind-on mechanism which moves the film on one frame each time the shutter is released.

AV - see Audiovisual.

Available light - term applying to light normally occurring in a scene, not supplemented by illumination intended specifically for photography.

Average metering - A special exposure metering technique that measures the average light intensity across the entire frame.

AVI A video format used by Microsoft Windows®.

Avant Garde. Photography tat is innovative in, style or subject matter Axis lighting - light pointed at the subject from a position close to the lens.

Azo dyes - compounds forming colors of great strength and purity. Used in camera filters and integral tripack dye-bleach materials.

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