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Photo 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.

•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.

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

•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.

•Acceptance angle - see Angle of View.

•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.

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

•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.

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.

•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.

•Afocal 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.

•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.

•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.

•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.

•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.

•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 .

•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-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.

Aperture - circular hole in the front of the camera lens which controls the amount of light allowed to pass on to the film.

•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.

•Aplanat - lens which has been corrected for spherical aberration.

•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.

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.

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

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.

•Artificial daylight - artificial light having a similar color temperature to daylight.

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

•Artificial light film - color film balanced for use ion tungsten Artificial light, usually 3200 K.

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.

•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.

•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.

•Assignment - definite OK to take photos for a specific client with mutual understanding as to the provisions and terms involved.

•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.

•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.

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 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.

•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.

•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.

Photo Glossary - B

B (Bulb) - letter on the shutter dial indicating that the shutter will stay open while the release is depressed.

•Back focus - distance between the back surface of the lens and the image plane, when the lens is focused at infinity.

•Background - area shown behind the main subject in a picture.

•Background density - density of any selection of a negative or print on which there is no image. Also referred to as Fog level.

•Backing - dark coating, normally on the back of a film, but sometimes between emulsion and base, to reduce halation. The backing dye disappears during processing.

•Back-lighting - light coming from behind the subject.

•Back printing - information printed on the back of a picture by the photofinisher. The system standard requires the printing of frame number, film cassette number and processing date automatically on the back of each Advanced Photo System print.

•Back projection - projection system often used to create location backgrounds in the studio.

•Bag bellows - short flexible sleeve used on large format cameras in place of normal bellows when short focal length lenses are employed.

•Balance - placement of colors, light and dark masses, or large and small objects in a picture to create harmony and equilibrium.

•Ball and socket - swiveling mount used to attach a camera to a tripod, consisting of a large ball joint designed to move in a cup.

•Ballistic photography - photography of weapons, ammunition and projectiles usually used for analysis.

Barium sulfate - compound used in the manufacture of photographic printing paper to give bright white highlights in the final print.

•Barn doors - accessory used on spotlights and flood lamps to control the direction of light and width of the beam.

Barrel distortion - one of the common lens aberrations, where straight lines at the edge of the field are caused to bend into the shape of a barrel.

•Baryta - coating of barium sulfate applied as the foundation to fiber based printing papers.

•Base - support for photographic emulsions. Available in a choice of materials, including paper, cellulose, triacetate, glass and estar.

•Baseboard camera - portable large format camera with a folding base-board. Allows a limited use of camera movements. Also referred to as a field camera.

•Base Exposure Time - initial exposure time used for making a "straight" print.

•Base-relief - photographic image effect usually produced by printing from a negative and a positive sandwiched together in the enlarger, slightly out of register.

•Batch numbers - set of numbers printed on packages of sensitive materials to indicate common production coating.

•Beam splitter - mirror and prism system capable of partly reflecting, partly transmitting light.

•Belitski's reducer - solution used as a chemical reducer for negatives. It consists of ferric potassium citrate or oxalate in an acid fixing solution.

•Bellows - light tight, folding sleeve which can be fitted between the lens and the film plane.

•Bellows shutter - obsolete shutter consisting of a pair of bellows that, when closed together, form a hemisphere enclosing the lens.

Between the lens shutter - shutter usually placed within the components of a compound lens close to the diaphragm.

•Bichromate - refers to potassium bichromate or potassium dichromate, used for bleaching and as a sensitizer for gelatin.

Bi-concave lens - simple lens or lens shape within a compound lens, whose surfaces curve toward the optical center. Such a lens causes light rays to diverge.

•Bi-convex lens - simple lens shape whose surfaces curve outward, away from the optical center. Such a lens causes light rays to converge.

•Binocular vision - visual ability to determine three dimensions. Stereoscopic photography depends on the use of binocular vision.

•Bi-pack - combination of two films, differently sensitized, but exposed as one.

•Bi-refringence - splitting of light passing through certain kinds of crystals into two rays at polarized right angles to each other.

•Bispheric lens - lens having different curvatures at the center and the edge, each of which forms part of a sphere. The different edge curvature brings the peripheral rays more closely to the same point of focus as the center rays.

•Bitumen - hydro-carbon which hardens by the action of light. It was used by Joseph Nicephore Niepce to produce the worlds first photograph in the early 19th century.

•Black silver - finely divided metallic silver formed from silver halides by exposure and development.

•Bleach - chemical bath capable of rehalogenizing black metallic silver.

•Bleaching - stage in most toning, reducing and color processing systems.

•Bleach-out - method of producing line drawings from photographic images. The photographic is processed in the normal way, its outlines sketched, and the black metallic silver image is then bleached away to leave a drawn outline.

•Bleed - term used to describe a picture with no borders, which has been printed to the edge of the paper.

•Blocked up - a portion of an overexposed and/or overdeveloped negative so dense with silver halides that texture and detail in the subject are unclear.

•Blocking out - method of painting selected areas of a negative with an opaque liquid on the non-emulsion side. Since light is unable to penetrate these areas they appear white on the final print.

•Blotter - sheet or sheets of absorbent material made expressly for photographic prints. Wet prints dry flat and quickly when placed between blotters.

•Blowup - enlargement; a print that is made larger than the negative or slide.

•Blue print - alternative term for cyanotype.

•Blue sensitive - sensitive to blue light only. All silver halides used in traditional black and white emulsions are sensitive to blue light, but early photographic materials had only this sensitivity.

•Blur - unsharp image areas, created or caused by subject or camera movement, or by selective or inaccurate focusing.

•Boom - adjustable metal arm, attached to a firm stand, on which lighting can be mounted. Some booms are also made to support cameras.

•Borax - mild alkali used in fine grain developing solutions to speed up the action of the solution.

•Border - edge of a photographic print - either left white, or printed black.

•Boric acid - compound used in certain fixers to prolong shier hardening life.

•Bounce light - light that is directed away from the subject toward a reflective surface.

•Box camera - simplest type of camera manufactured, and first introduced by George Eastman in 1888. It consists of a simple, single element lens, a light tight box and a place for film in the back.

•Bracketing - technique of shooting a number of pictures of the same subject and viewpoint at different levels of exposure.

•Brightfield - method of illumination used in photomicrography which will show a specimen against a white or light background.

•Brightline viewfinder - viewfinder in which the subject is outlined by a bright frame, apparently suspended in space. This may show parallax correction marks, or lines indicating the fields of view of different focal lengths.

•Brightness range - subjective term describing the difference in illumination between the darkest and lightest areas of the subject.

•Brilliance - intensity of light reflected from a surface. It is sometimes an alternative term for luminosity.

•Broad lighting - portrait lighting in which the main light source illuminates the side of the face closes to the camera.

•Brometching - obsolete, special method of producing a bromide print. The result acquired the texture of its support and appeared similar to an etching.

•Bromide paper - most common type of photographic printing paper. It is coated with an emulsion of silver bromide to reproduce black & white images.

•Bromoil process - old printing process invented in 1907, consisting of three stages. First, an enlargement is made on bromide paper and processed. Second, the silver image is removed in a bleacher which also modifies the gelatin so it will accept lithographic ink. Third, while still damp the gelatin is inked up by hand to create the image.

•Brownie - trade name given to early Kodak box cameras.

•Brush development - method of development in which developer is applied to the material with a brush or similar instrument.

•BSI - abbreviation for British Standards Institute.

•Bubble chamber photography - method of analyzing the paths of high-speed sub-atomic particles.

•Buffer - chemical substance used to maintain the alkalinity of a developing solution, particularly in the presence of bromine which is produced during development.

•Built-in meter - reflective light meter built directly into the camera so that exposures can be easily made for the cameras position.

•Bulb - See B.

•Bulk film - film purchased in long lengths. Used in a bulk camera back or with a bulk film loader.

•Burning in - see Printing-in.

•Butterfly lighting - lighting in which the main source of light is -placed high and directly in front of the subject.

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