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.
•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 Å.
•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.
•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.
Photography 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.
•C-41 - Kodak's standard chemical process for developing color negative film.
•Cable release - flexible cable used for firing a camera shutter. Particularly useful for slow shutter speeds and time exposures, when touching the camera may cause camera vibration and blurring of the image.
•Cadmium sulfide cell (CdS) - photo-sensitive cell used in exposure meters. Fed by an electric current from a battery, its electrical resistance varies according to the amount of light it receives.
•Callier effect - contrast effect in photographic printing caused by the scattering of directional light from an enlarger condenser system. The negative highlights are of high density and scatter more light with little or no scattering from negative shadow areas, which are of low density. This gives a print higher contrast than a contact print.
•Calotype process - first negative/positive process, invented by W.H. Fox Talbot in 1839. Paper was coated with silver iodide and a solution of silver nitrate and gallic acid. After exposure the paper was developed in a silver nitrate solution.
•Camera angles - various positions of the camera with respect to the subject being photographed, each giving a different viewpoint and perspective.
•Camera lucida - lens and prism system through which a virtual image was seen, apparently appearing on the surface of the drawing paper.
•Camera movements - mechanical systems most common on large format cameras which provide the facility for lens and film plane movement from a normal standard position.
•Camera obscura - origin of the present day camera. In its simplest form it consisted of a darkened room with a small hole in one wall. Light rays could pass through the hole to transmit on to a screen, and inverted image of the scene outside. It was first mentioned by Aristotle in the 4th Century B.C. and developed through the centuries as an aid to drawing.
•Camera shake - movement of the camera caused by an unsteady hold or support. It is a major cause of un-sharp pictures, especially with long focus lenses.
•Canada balsam - liquid resin with a refractive index similar to glass. It is used for bonding elements in compound lenses.
•Candela - unit which expresses the luminous intensity of a light source.
•Candid pictures - unposed pictures of people and animals, often taken without the subject's knowledge. These usually appear more natural and relaxed than posed pictures.
•Candle meter - also known as a lux and defined as the illumination measured on a surface at a distance of one meter from a light source of one international candle power.
•Candle meter second - unit of illumination related to exposure time, more often referred to as one lux-second.
•Capacitor - device that builds and stores electrical charges. Used in electronic flash and some forms of electronic shutters.
•Capping shutter - extra shutter used in some medium format cameras or in conjunction with a group of extreme high speed shutters.
•Carbon arc - see Arc lamp.
•Carbon process - contact printing process, introduced in 1866, using tissue coated with pigmented gelatin. The paper was sensitized in potassium bichromate and contact printed behind a negative in sunlight.
•Carbon tetrachloride - liquid used for removing grease and finger prints from negatives.
•Carrier - frame that holds a negative flat for enlarging.
•Carte-de-visite - portrait photograph on a mount about the size of a postcard. Introduced in 1854, carte-de-visite became a social craze in many countries during the 1860s.
•Cartridge - quick loading film container. pre-packed and sealed by the manufacturer.
•Cassette - light tight metal or plastic container holding measured lengths of 35mm or medium format film, which may be loaded straight into the camera.
•Cast - overall bias toward one color in a color photograph.
•Catadioptric lens - see Mirror lens.
•Catchlight - reflection of a light source in the subjects eyes.
•Cathode ray tube - evacuated bulb of glass containing pairs of plates between which electrodes pass.
•Caustic potash - high alkaline used in high contrast developing solutions to promote vigorous development. Highly corrosive and poisonous.
•Caustic soda - see Caustic potash.
•CCD - electronic sensor used by all autofocus cameras, capable of detecting subject contrast.
•CC filter - abbreviation for color compensating filter.CC filters are designed primarily for introducing or correcting color bias at the camera exposure stage.
•Centigrade - scale of temperature in which the freezing point of water is equal to 0° and boiling point to 100° C.
•Changing bag - opaque fabric bag, which is light tight and inside sensitive materials may be handled safely.
•Characteristic curve - performance graph showing the relationship between exposure and density under known developing conditions. It can provide immediate comparative information on factors such as emulsion speed, fog level, and contrast effect. The study of photographic chemicals in this way is known as sensitometry.
•Chemical focus - point at which a lens brings the actinic rays to focus. In a modern fully corrected lens, chemical and visual focus coincide.
•Chemical fog - even, overall density on film or paper. It is exaggerated by over-development.
•Chemical reducer - see Reducers.
•Chemical vapor - method of exposing negatives in a closed container to a small amount of mercury of sulfur dioxide. After approximately 24 hours the film is developed normally. It produces interesting yet very inconsistent results.
•Chiaroscuro - light and shade effect. The way in which objects can be emphasized by patches of light, or obscured by shadow.
•Chloride paper - printing paper with a silver chloride emulsion. Much less sensitive than bromide paper. Mainly used for contact printing.
•Chlorobromide paper - photographic paper coated with an emulsion made up of both silver chloride and silver bromide. Used for producing enlargements with a warm, slightly brownish-black image, especially if processed in a warm tone developer.
•Chlorquinol - alternate term for chlorhydroquinone.
•Chromatic aberration - inability of a lens to bring light from the same subject plane but of different wavelengths to a common plane of image or focus.
•Chromaticity - objective measurement of the color of an object or light source.
•Chromatype - early type of extremely slow paper used for contact printing.
•Chrome alum - alternative term for potassium chromium sulfate.
•Chromogenic development - process in which the oxidation products of development combine with color couplers to form dyes during processing.
•Chromogenic materials - color photographic materials which form dyes during processing.
•Chronocyclograph - photograph used for the analysis of complex cyclic movements.
•Chronophotography - technique pioneered by Eadweard Muybridge, for recording objects in motion by taking photographs at regular intervals.
•Cibachrome - color printing process that produces color prints directly from color slides.
•CIE standard - system of standards adopted by the Commission Internationale de I'Eclairage, allowing accurate descriptions of colors.
•Circle of confusion - disks of light on the image, formed by the lens from points of light in the subject. The smaller these disks are in the image the sharper it appears.
•Clayden effect - desensitizing of an emulsion by means of exposure to a strong, brief flash of light.
•Clearing agent - processing solution used to remove stains or to cancel out the effect of chemicals left on the sensitive material left from previous stages in the process.
•Clearing time - length of time needed for a negative to clear in a fixing solution.
•Clear-spot focusing - method of lens focusing achieved by examining the image through a transparent area in a specific plane.
•Cliche-verre - designs painted on glass in varnish or oil paint, or scratched into the emulsion of a fogged and processed plate using an etching needle. The results are then printed or enlarged on photographic printing paper.
•Click-stops - lens aperture controls using a series of bearings that click audibly into place at each numbered setting.
•Clip test - short sample of film, cut from the main exposed roll, used to determine the appropriate development and/or fixing time.
•Close-up - general term for an image of a close subject, i.e. filling the frame.
•Close-up attachment - accessory that enables a camera to focus on subjects nearer than the lens normally allows.
•Close-up lens - see Close-up attachment.
•CMYK - abbreviation for cyan, magenta, yellow and black. It is the colors used in a four color printing process.
•Coated lens - lens with air-glass surfaces which have been coated with magnesium fluoride to reduce lens flare.
•Coherent light - light waves that vibrate with constant phase relationships. They can be produced by a laser or a combination of two prisms.
•Coincidence rangefinder - see Rangefinder.
•Cold cathode illumination - low temperature fluorescent light source common in many diffuser enlargers, which is inclined to reduce contrast and edge definition.
•Cold colors - colors at the blue end of the spectrum that suggest a cool atmosphere.
•Cold-light enlarger - enlarger using cold cathode illumination. A diffusion type of enlarger. These types of enlarger heads scatter the light more evenly across the surface of the negative. One advantage of the cold light head is that it can render more subtle tonal gradations and will minimize the effect of dust and scratches on the negative which are translated to the print.
•Collage - composition employing various different materials combined with original artwork attached to some type of backing.
•Collodion process - also known as "wet collodion" was invented by Frederick Scott Archer in 1851-52. It was a great improvement over the earlier calotype process because because of the large increase in speed gained by exposing the plate while still "wet", but it had the disadvantage of requiring bulky equipment.
•Color balance - adjustment in color photographic processes ensuring that a neutral scale of gray tones is reproduced accurately.
•Color balancing filters - filters used to balance color film with the color temperature of the light source and prevent the formation of color casts.
•Color circle - chart of spectrum hues presented as a circle.
•Color compensatory filters - pale colored filters used to warm or cool subject colors.
•Color contrast - subjective judgment on the apparent luminous difference or intensity of two colors when placed close to one another.
•Color conversion filter - see CC filters.
•Color developer - developer designed to reduce exposed silver halides of black silver and at the same time create oxidation byproducts that will react with color couplers to form specific dyes.
•Color development - chemical treatment in the color processing cycle that produces the colored dye image.
•Color head - enlarger illumination system that has built-in adjustable filters for color printing.
•Color masking - pink or orange mask built into color negative film to improve final reproduction on the print.
•Color mixing - practical application of either additive or subtractive color synthesis.
•Color Negative - film designed to produce color image with both tones and colors reversed for subsequent printing to a positive image, usually on paper.
•Color reversal - film designed to produce a normal color positive image on the film exposed in the camera for subsequent viewing by transmitted light.
•Color saturation - purity or strength of color, due to the absence of black, white or gray.
•Color sensitivity - response of a sensitive material to colors of different wavelengths.
•Color sensitometry - method of determining the sensitivity of color materials.
•Color separation - process of photographic an image through filters to produce three black and white negatives that represent red, green and blue content.
•Color synthesis - combinations of colored light or dye layers that will collectively produce a colored image.
•Color temperature - way of expressing the color quality of a light source. The color temperature is measured in Kelvin (K).
•Color temperature meter - device for measuring the color temperature of a light source.
•Color toning - system of changing the color of a black and white photograph by converting black metallic silver into a colored compound.
•Color weight - visual characteristic of fully saturated colors. Some of these colors appear darker than others. A color's visual weight may have a different appearance to the eye to its appearance on film.
•Coma - lens aberration producing asymmetrical distortion of points in the image.
•Combination printing - producing a composite image by printing more than one negative on a single sheet of paper.
•Compact camera - camera designed to allow easy portability or concealment.
•Compensating developer - developer designed to compress the general contrast range in a negative without influencing gradation in the shadow and highlight areas.
•Compensating positive - image on translucent material that can be printed together with the negative of the same image. When combined the result makes printing contrasty negatives easier.
•Complementary color - color of light which, when combined with another specified color in the correct proportions, will form gray or white.
•Completion - state of development when all the exposed silver halides have been reduced to metallic silver, and the image density will not increase with further development.
•Composite printing - alternative term for combination printing.
•Compound lens - lens system consisting of two or more elements. Compound lens designs can allow the lens designer to reduce lens aberrations, making maximum apertures larger and improve resolution.
•Compound shutter - shutter consisting of a number of metal leaves arranged symmetrically around the edge of the lens barrel.
•Compur shutter - well known German brand of compound shutter.
•Concave lens - see Bi-concave lens.
•Condenser - optical system which concentrates light rays from a wide source into a narrow beam. Condensers are used in spotlights and enlargers.
•Condenser enlarger - enlarger with a sharp, undiffused light that produces high contrast and high definition in a print.
•Cones - sensory organs on the retina of the eye, allowing color vision.
•Constructivism - art movement that begun in Russia c. 1913. Characterized by the use of everyday materials in abstract compositions.
•Contact paper - printing paper used only for contact printing. It is usually coated with a silver chloride emulsion of very slow speed.
•Contact print - negative sized photograph made by exposing printing paper in direct contact with the negative.
•Contact printer - apparatus used for making contact prints. Equipment ranges from a contact printing frame to more sophisticated boxes with safe lighting.
•Contact screen - type of half-tone screen in which the dots consist of slightly unsharp halos. Used to make half-tone images.
•Contamination - traces of chemicals that are present where they don't belong.
•Continuous tone - term applied to monochrome negatives and prints, where the image contains a gradation of density from white through gray to black, which represents a variety of subject luminosities.
•Contour film - special print film producing a equidensity line image from a continuous tone negative or print.
•Contrast - subjective judgment of the difference between densities or luminosities and their degree of tonal separation in a subject, negative or positive print.
•Contrast filters - filters used in black and white photography to darken or lighten the films rendition of particular colors in the subject.
•Contrast grade - numbers (usually 1-5) and names (soft, medium, hard, extra-hard, and ultra hard) of the contrast grades of photographic papers.
•Contrast values - perceived difference between the light areas (highlights) and the dark areas (shadows) of a scene. The range of contrast levels between the highlights and the shadows is called Contrast Values.
•Contrasty - negative, print or scene with great differences between the highlights and shadows.
•Contre-jour - backlighting. A photograph taken with the camera pointed directly at the light source.
•Converging lens - see Convex lens.
•Convertible lens - compound lens made in two sections, the elements of which are arranged so that when one part is unscrewed it provides a new lens with approximately twice the original focal length.
•Cooke triplet - one of the most important lenses in lens history, designed by H.D. Taylor in 1893. It consists of three basic elements and has a maximum aperture of 16.3. It is the basic design that most normal focal length lenses of today have evolved.
•Copper chloride - chemical contained in certain bleaches, toners, intensifiers, and reducers.
•Copper sulfate - chemical contained in certain bleaches, toners, intensifiers, and reducers.
•Copper toning - chemical process used for toning monochrome prints. See Toners.
•Copyright laws - laws which govern the legality of ownership of a particular photographer or piece of work.
•Correction filter - filter which alters the color rendition of a scene to suit the color response of the eye.
•Coupled rangefinder - system of lens focusing which combines the rangefinder and the focusing mechanism, so that the lens is automatically focused as the rangefinder is adjusted.
•Coupler - chemical present in different forms in all three layers of substantive color or a chemical incorporated into a developer.
•Covering power - maximum area of image of usable quality, which a lens will produce.
•Coving - plain curved background which has no edges, corners or folds and gives the impression of infinity.
•CP filters - abbreviation for color printing filters.
•C-print - any enlargement from a color negative.
•Critical aperture - setting at which a lens gives its best performance. The setting offers the best compromise between diffracting due to small aperture and lens aberrations apparent at wide apertures.
•Cronographic camera - camera used to photograph the sun.
•Cropping - omitting parts of an image when making a print or copy negative in order to improve the composition of the final image.
•Crossed polarization - system of using two polarizing filters, one over the light source and one between the subject and the lens. With certain materials crossed polarization causes bi-refringent effects which are exhibited as colored bands. Used in investigations of stress areas in engineering and architectural models.
•Cross front - camera movement which allows the lens to be moved laterally from its original position.
•Crown glass - low dispersion optical glass.
•Cubism - early twentieth century European art movement characterized by the rendering of forms as simplified planes, lines and geometric shapes.
•Curvilinear distortion - combination of barrel distortion and pincushion distortion.
•Curvature of field - lens aberration causing a curved plane of focus.
•Cyan - blue-green subtractive primary color which absorbs red and transmits blue-green.
•Daguerreotype - first practical and commercial photographic process, introduced by Louis Daguerre in 1839. The sensitive material comprised silver iodide, deposited on a polished silver plated copper base. A positive image was produced by camera exposure and mercury "development", which turned light struck halides gray-white. The image was made permanent by immersing the plate in a solution of sodium chloride.
•Darkcloth - cloth made of dark material placed over the photographers head and the camera back to facilitate the viewing of images on the ground glass screen of sheet film cameras.
•Darkfield - method of illumination used in photomicography that will show a specimen against a dark or black background.
•Darkroom - light tight room used for processing and printing. It usually incorporates safe lighting suitable for the materials in use.
•Darkslide - slide-in plastic sheet used on sheet film cameras over the front of the film holder to protect the emulsion from light.
•Daylight enlarger - early type of enlarger using light from a hole in a window to provide illumination of the negative.
•Daylight color film - color film intended for use with daylight or a light source of similar temperature. The film is color balanced to 5400 K.
•Daylight tank - light tight container for film processing.
•Dedicated flash - flash gun designed to integrate automatically into a cameras exposure reading and shutter circuitry.
•Definition - subjective term for the clarity of a negative or print.
•Delayed action - operation of the shutter some time after the release is depressed. Most shutters have a delayed action timer built in.
•Dense - describes a negative or an area of a negative in which a large amount of silver has been deposited.
•Densitometer - instrument for measuring the density of silver deposits on a developed image by transmitted or reflected light.
•Density - amount of silver deposit produced by exposure and development. It is measured in terms of the logarithm of opacity, where opacity is the light stopping power of a medium.
•Depth of field - distance between the nearest point and the farthest point in the subject which is perceived as acceptable sharp along a common image plane.
•Depth of field scale - scale on a lens barrel showing the near and far limits of depth of field possible when the lens is set at any particular focus and aperture.
•Depth of focus - distance which the film plane can be moved while maintaining an acceptably sharp image without refocusing the lens.
•Desensitizing - reducing an exposed emulsion's sensitivity to light. This can be done by the application of dyes or by using oxidation agents.
•Detective camera - popular Victorian camera which was designed to appear as a bowler hat, pocket watch or binoculars.
•Developer - chemical bath containing reducing agents, which converts exposed silver halides to black metallic silver, making the latent image visible.
•Development - process of converting exposed silver halides to a visible image.
•Diaphragm - term used to describe the adjustable aperture of a lens. It controls the amount of light passing into the camera and may be in front of, within or behind the lens.
•Diaphragm shutter - between the lens camera shutter that performs the function of the iris diaphragm.
•Diapositive - positive image produced on a transparent support for viewing by transmitted light, i.e. transparency.
•Diazo - abbreviation of diazonium compounds, which decompose under the action of intense blue or ultraviolet radiation, forming an image in an azo dye.
•Dichroic - displaying two colors - one by transmitted and one by reflected light.
•Dichroic filters - produced by metallic surface coatings on glass to form colors by interference of light. Used in high quality color enlarger heads.
•Dichroic fog - purple-green bloom usually seen on negatives and caused by the formation of silver in the presence of an acid.
•Differential focusing - setting the camera controls to produce minimum depth of field, so that image sharpness is limited to a particular subject element.
•Diffraction - light rays scattered and change direction when they are passed through a small hole or close to an opaque surface.
•Diffraction grating - optical attachment that separates light into its constituent colors.
•Diffuse lighting - lighting that is low or moderate in contrast, such as on an overcast day.
•Diffuser - any material that can scatter or diffuse light. The effect is to soften the character of light. The closer a diffuser is to a light source the less it scatters light.
•Diffusing - process of softening detail in a print with a diffusion disk or other material that scatters light.
•Diffusion condenser enlarger - enlarger that combines diffuse light with a condenser system, producing more contrast and sharper detail than a diffusion enlarger but less contrast than a condenser enlarger.
•Diffusion enlarger - enlarger that scatters light before it strikes the negative, distributing light evenly on the negative. Detail is not as sharp as with a condenser enlarger.
•Dilution - reduction in the strength of a liquid by mixing it with an appropriate quantity of water.
•Dimensional stability - substance's ability to remain unchanging in size when subjected to processing and drying.
•DIN speed - system used by the German Standards Organization.
•Diopter - unit used to express the power of a lens. It is the reciprocal of the focal length expressed in meters.
•Direct vision viewfinder - sighting device with which the subject is viewed directly, without the aid of a prism or mirror.
•Discharge lamp - light source that provides illumination when an electrical charge is applied to gas particles in a glass tube. An example of this device is electronic flash.
•Dish development - method of development used for processing single sheet, cut film or paper by immersing in a shallow dish of developer and agitating by rocking the dish.
•Dispersion - ability of glass to bend light rays of deferent wavelengths to varying degrees.
•Distance symbols - symbols used on the focus control of simple cameras, as a focusing guide.
•Distortion - alteration in shape and/or proportions of an image.
•Diverging lens - lens which causes rays of light coming from the subject to bend away from the optical axis.
•Documentary photography - taking of photographs to provide a record of social and political situations with the aim of conveying information.
•Dodging - control of exposure in photographic printing achieved by reducing exposure to specific areas of the paper.
•Dolly - frame with lockable wheels, designed to support s tripod, and allow easy movement around a studio.
•Double exposure - see Multiple exposure.
•Double extension - characteristic of large format cameras which enables the bellows to be extended to twice that of the focal length of the lens in use. It is used for close-up photography.-
•Drop-in-loading - feature in all Advanced Photo System cameras that virtually eliminates film-loading problems by automatically accepting the leader less cassette.
•Dry down - refers to the amount a print darkens after drying.
•Drying cabinet - vented cabinet equipped with suspension clips for drying films.
•Drying marks - marks on the film emulsion caused by uneven drying and resulting in areas of uneven density, which may show up in the final print.
•Dry mounting - method of attaching prints to mounting surfaces by heating shellac tissue between the mount and the print.
•Dry plates - term used to describe gelatin coated plates in the days when wet collodion process was still popular.
•DX coding - method, whereby films can automatically set the film ISO speed.
•Dyad - pair of complementary colors or any two colors considered visually harmonious.
•Dye coupling - process creating a colored image from the reaction between by-products of color development and couplers.
•Dye destruction process - method of producing a colored image by partially bleaching fully formed dye layers incorporated in the sensitive material.
•Dye-image monochrome films - black & white negative films designed for color processing.
•Dye sensitizing - defined as all silver halides used in black & white emulsions are sensitive to blue light. Early photographic materials possessed only this sensitivity.
•Dye transfer print - method of producing color prints via three color separation negatives. Negatives are used to make positive matrixes, which are dyed in subtractive primaries and printed in register.
•Dynamism - picture structuring which relates to a sense of movement and action.
Photography Glossary - E
•E6 - Kodak's standard chemical process for developing Ektachrome or compatible slide films.
•Easel - device to hold photographic paper flat during exposure, usually equipped with an adjustable metal mask for framing.
•Eberhard effect - border effect occurring in a developed image. It appears as a dense line along an edge of high density and as a light line along an edge of low density. It occurs most often in plates developed flat in solution that is not sufficiently agitated. The effect was described by Gistav Eberhard in 1926.
•Edge numbers - reference numbers printed by light at regular intervals along the edge of 35mm and roll films during manufacture.
•Effective aperture - diameter of the bundle of light rays striking the first lens element that actually pass through the lens at any given diaphragm setting.
•EIS - Electronic Image Stabilizer. A feature that minimizes effect of camera shake.
•Electroluminescence - conversion of electric energy directly into visible light.
•Electronic flash - artificial lighting produced by an electronic discharge in a gas filled tube. A single tube can produce a large number of flashes.
•Electronic shutter - shutter system timed by electronic rather than mechanical means.
•Electrophotography - creation of images by alteration to the electrical properties of the sensitive material as a result of the action of light.
•Element - single lens shaped piece of glass that forms part of a compound lens system.
•Elon - another term for Methylaminophenol sulfate. It is more commonly known as metol.
•Emulsion side - side of the film coated with emulsion.
•Endoscope - optical device allowing the viewing and photography of small inaccessible subjects.
•Enhanced back printing - Advanced Photo System feature available in some cameras that enables users to encode detailed information at the time of picture-taking.
•Enlargement - term used to describe a print larger than the negative used to produce it.
•Enlargement ratio - ratio denoting the amount of linear (not area) enlargement between a print and the negative from which it is made.
•Enlarger - apparatus for producing prints by projecting a negative or transparency on sensitive paper.
•Enprint - small enlarged print, with dimensions of a fixed ration, produced commercially in an automatic printer. Usually 3 ½" wide.
•Entrance pupil - size of the beam of light which, entering the elements of a compound lens that are in front of the aperture, completely fills the iris diaphragm.
•Equivalent focal length - distance in a lens between the front nodal point and the focal plane when the lens is set to focus a subject at infinity. In a telephoto lens the equivalent focal length is shorter than the back focus. The reverse is true in a wide angle lens.
•Etch - process of removing small imperfections in a print or negative by scraping away part of the emulsion.
•Etching - dissolving away selected areas of a surface while shielding the other portions with a resistant. The process is used as a creative drawing medium as well as for making half-tone plates on copper or zinc.
•Ever-ready case - camera case that can be opened, allowing the camera to be used without removing it. A front flap hinges down to uncover the lens, viewfinder and camera controls.
•Everset shutter - simple camera shutter mechanism on which a single depression of the release both tensions and fires the shutter.
•Exit pupil - image of the iris diaphragm formed on the back surface of a compound lens by the elements behind the aperture.
•Expiry date - date stamp on most film boxes indicating the useful life of the material in terms of maintaining its published speed and contrast.
•Exposure - product of the intensity of light and the time the light is allowed to act on the emulsion (I x T = E).
•Exposure index - see Speed.
•Exposure latitude - amount by which it is possible to over or underexpose a light sensitive material and, with standard processing, still produce acceptable results.
•Exposure meter - instrument for measuring the amount of light falling on or being reflected by a subject.
•Exposure value (EV) - scale of values used to indicate the sensitivity range of a TTL or off-camera meter system within which accurate exposure measurement is guaranteed.
•Extension bellows - device used to provide the additional separation between lens and film required for close-up photography.
•Extension tubes - metal or plastic tubes used on small format cameras, to extend lens-to-film distance, enabling magnification greater than 1x.
•Extinction meter - early type of exposure calculator.
•Factor - number that tells how many times exposure must be increased in order to compensate from loss of light.
•Fahrenheit scale - scale of temperature named after its German originator, G. D. Fahrenheit. On this scale, the freezing point of water is 32° F, and the boiling point of water is 212° F.
•False attachment - part of one object seen behind another so that lines, shapes or tones seem to join up. A composition device used in various ways to produce images in which foreground and background objects appear to occupy the same plane.
•Farmer's reducer - used for bleaching negatives and prints.
See reducers
See reducers
•Farraday shutter - high-speed shutter using a pair of crossed polarizers, between which is a glass block within a coil. When a voltage passes through the coil, the plane of polarization changes, allowing light to pass through the second polarizer.
•Fast film - film which has an emulsion that is very sensitive to light. These films have high ISO ratings.
•Fast lens - lens with a wide maximum aperture (low f number).
•Ferric chloride - bleaching solution used on negative materials.
•Ferrotype process - method of creating direct positive images with dark enameled metal plates as a base. Also known as the tin-type process.
•Fiber based paper - photographic paper without a resin coating. Processing times are longer than for other papers, but the paper is more archivally permanent.
•Field camera - sheet film camera suitable for use in location work.
•Fill light - source of illumination that lightens shadows. See Fill-in.
•Film - photographic material consisting of a thin transparent plastic base coated with a light sensitive emulsion.
•Film characteristic curve - describes a graphical relationship between the logarithm of the exposure value (horizontal axis) and density (vertical axis) of film. Each brand of film exhibits a different characteristic curve.
•Film clips - metal or plastic clips used to prevent the curling of a length of drying film.
•Film holder - light tight container to hold sheet film.
•Film pack - container holding several sheets of film, so devised that when fitted to the camera the photographer can pull a tab to remove an exposed sheet and replace it with another. Film packs are typical with Polaroid film.
•Film speed - see Speed.
•Filter factor - number by which an unfiltered exposure reading must be multiplied to give the same effective exposure through the filter. This compensates for the absorption of light by the filter. This process is unnecessary with TTL metering systems as long as the filter is attached during the metering process.
•Filters - colored glass, gelatin or plastic disks, which modify the light passing through them, mainly in terms of color content. They can be used at the camera or printing stages.
•Finality development - prolonged development, reducing silver halides affected by light to silver until no further image density improvement occurs.
•Finder - abbreviation for viewfinder.
•Fine grain developers - film developers which help to keep grain size in the photographic image to a minimum.
•Fisheye lens - extreme wide-angle lens with an angle of view exceeding 100° and sometimes in excess of 180°. Depth of field is practically infinite and focusing is not required.
•Fixation - chemical bath which converts unused halides to a soluble silver complex in both negatives and prints, making the image stable in white light.
•Fixed focal length - camera system whose lens cannot be interchanged for a lens of different focal length.
•Fixed focus - lens camera system that has no method of focusing on a fixed point, usually at the hyperfocal distance.
•Fixer - chemical solution used for fixation.
•Flare - non-image forming light scattered by the lens or reflected from the camera interior.
•Flash - artificial light source giving brief but very bright illumination. It is produced by a combination of certain gases within a transparent tube. There are two types; electronic, which may be used repeatedly, and expendable in which the bulb can be used only once.
•Flash bulb - replaceable bulb for use in expendable flash units. A glass bulb contains a pyrotechnic wire or paste which burns out in a brilliant flash when a low voltage firing current is applied.
•Flash cube - obsolete bulb containing four small flash bulbs built into a single unit.
•Flash factor - number which provides a guide to correct exposure when using flash. See also Guide number.
•Flashing - briefly and evenly exposing photographic materials to white light.Often used to lower contrast of printing paper, when the flashing exposure is made in addition to the regular exposure.
•Flash powder - chemical powder consisting of a mixture of metallic magnesium and an oxidizing agent. Ignited by heat to produce a brilliant flash of light.
•Flash synchronization - method of synchronizing flash light duration with maximum shutter opening. There are usually two settings on a camera, X and M. X is the setting used for electronic flash. M is for most expendable types of flash (bulbs) which require a delay in shutter opening.
•Flat - used to describe a negative or print with very low contrast.
•Flat-bed camera - camera designed for copying artwork and documents. Mounted on a vertical column, like an enlarger, allowing the photographer to accommodate different documents or artwork for duplication.
•Flat gradation - subjective term used to describe low-contrast values.
•Flat lighting - lighting that produces very little contrast or modeling on the subject and a minimum of shadows.
•Floating elements - one or more elements in a lens which adjust position relative to other components during focusing or zooming. Used to maintain correction of lens aberrations at all settings.
•Floodlight - artificial light source with a dish shaped reflector and a 125-500+ watt tungsten filament lamp producing evenly spread illumination over the subject.
•Fluorescent whites - brilliant highlights produced by applying a fluorescent agent to a printing paper base. The print can also be treated after washing with a fluorescent whitener or dye solution.
•f numbers -e numbers on the lens barrel indicating the size of the aperture relative to the focal length of the lens. f numbers are calculated by dividing the focal length of the lens by the effective diameter of the aperture.
•Focal length - distance between the rear nodal point of the lens and the focal plane, when the focus is at infinity.
•Focal plane - imaginary line perpendicular to the optical axis which passes through the focal point. It forms the plane of sharp focus when the lens is set at infinity
•Focal plane shutter - shutter which lies just in front of the focal plane. Light sensitive film positioned at the focal plane is progressively exposed as the shutter blinds move across it.
•Focal point - point of light on the optical axis where all rays of light from a given subject meet at a common point of sharp focus.
•Focus - position in which rays of light from a lens converge to form a sharp image.
•Focusing - system of moving the lens in relation to the image plane so as to obtain the required degree of sharpness of the film.
•Focusing cloth - dark cloth used in view camera photography.
•Focusing hood - light proof cowl used on TLR and most roll film SLR cameras to prevent extraneous light falling on the focusing screen.
•Focusing magnifier - device to magnify the optical image and aid visual focusing.
•Focusing scale - scale of distances marked on a lens focusing ring.
•Focusing screen - ground glass screen fixed to the camera at the image-forming plane, enabling the image to be viewed and focused.
•Focus range - range within which a camera is able to focus on the selected picture subject.
•Fogging (Fog) - produces an overall veil of density on a negative or print, which does not form part of the image. It can be achieved by chemicals or exposing the sensitive material to light.
•Foreground - area in an image closer than the main subject.
•Format - size of negative paper or camera viewing area.
•Frame 1. single exposure on a roll of film. 2. viewfinder image boundary.
3. Decorative border applied to finished, mounted prints.
3. Decorative border applied to finished, mounted prints.
•Frames per second (fps) - used to describe how many frames can a motor drive or winder handle automatically.
•Free working distance - distance between the front of the lens and the subject.
•Fresnel lens - condenser lens used on a spotlight to gather together the rays of light coming from a source and direct them into a narrow beam.
•Fresnel magnifier - condenser lens used at the center of some ground glass viewing screens to aid focusing.
•Frilling - wrinkling and separation of the emulsion along the edges of its support material.
•Front curtain synchronization - when the flash fires an instant after the front curtain of a focal plane shutter has completed its travel across the film plane.
•Front element focusing - system of lens focusing in which only the front component of a compound lens moves backward and forward to adjust focus.
•Front projection - method of projection which allows you to combine a figure in a studio with a previously photographed background scene. The image is projected from the camera position onto a special reflective background screen.
•F stop - number that equals the focal length of the lens divided by the diameter of the aperture.
•Full scale print - print having a wide range of tonalities.
•Futurism - art movement started in Italy c. 1910, characterized by an aggressive rejection of tradition, and the representation of the dynamic movement of machinery.
•Galvanography - technique of electroplating a gelatin relief image created photographically to produce a photomechanical printing plate.
•Gamma - measurement used in sensitometry to describe the angle made between the straight line portion of the characteristic curve of the photograph emulsion and the base of the graph. The gamma is the tangent of the angle so formed.
•G curve - average gradient of a characteristic curve, describing similar characteristics to gamma, but measuring the slope from a line joining the lower and upper limits of the curve actually used in practice.
•Gelatin - natural protein used as a transparent medium to hold light sensitive silver halide crystals in suspension, binding them to the printing paper or film, yet swelling to allow entry of processing solutions.
•Gelatin filters - filters cut from dyed gelatin sheets and held in front of the lens or studio light.
•Gelatin sugar process - daylight printing process using paper with a sugar and dichromate coating, which hardens on exposure to light.
•Ghost images - bright spots of light, often taking the shape of the aperture, which appear in the camera viewfinder or in the final photograph when a lens is pointed at a bright light like the sun. Ghost images have been almost eliminated through the use of multi layer coatings of the lens elements.
•Glaze - glossy surface produced on some (non resin coated) printing papers. It is achieved by placing a wet print to to a heated drum or clean polished surface. Glazed print produce denser medium blacks than their matte counterparts.
•Glazer - machine on which wet fiber base prints are placed face down in contact with a polished surface, such a chromed steel, and held by tension. The surface is then heated to dry the print.
•Glossy paper - printing paper with a smooth shiny surface finish to give maximum detail and tonal range.
•Gold chloride - soluble chemical used in gold toners.
•Gold mean - compositional technique used to determine the "ideal" position of the main subject in the frame. It is based on creating a rectangle from a square. A line drawn from the center of one side of the square to the opposite corner becomes the radius of an arc. The side of the square is then protracted until it meets the arc, and from this point a rectangle is constructed. The side of the square which remains in the rectangle indicates the point at which the subject should be placed.
•GOST - arithmetical system of rating film speed used in Soviet bloc countries.
•Graduated filter - filter with a colored section, which gradually reduces in density toward the center of the filter. The rest of the filter is clear. Also referred to as a Graduated filter
•Gradation - tonal contrast range of an image.
•Grade - system of terms and numbers used to denote the contrast characteristics of black and white printing papers.
•Graduate - vessel used for measuring liquids.
•Grain - clumps of silver-halide grains in film and paper that constitute the image. These grains are produced both in the exposure process (film grain) and in the development process (paper grain). Unlike film, the grain in printing paper is largely responsible for the image tone.
•Graininess - clumps of silver halide crystals in the emulsion which are visible to the human eye because of spaces between the crystals.
•Grains - exposed and developed silver halides which have formed black metallic silver grains, producing the visible photographic image.
•Granularity - objective term describing the amount that silver halide grains have clumped together within the emulsion.
•Gray card - card with an 18 percent gray tint (reflectance) used to determine exposure by taking a meter reading from subject light reflected by the card.
•Ground glass screen - translucent glass sheet used for viewing and focusing the image on all large format and some reflex cameras.
•Guide number - term sometimes used to describe a flash factor, which provides a guide to correct exposure when using flash.
•Gum arabic - water soluble gum obtained from the Acacia tree and used in coatings of a number of photographic processes.
•Gum bichromate - contact printing process once very popular for the manipulative, impressionistic effects it makes possible. Drawing paper is coated with a mixture of gum, potassium bichromate and a pigment of any chosen color. This is then exposed to light behind a negative. Also known as the photo aquatint process.
•Gum platinum process - combination of gum and platinum printing.
•Gyroscopic camera mount - device employing a gyroscope to help stabilize hand held cameras subject to movement or vibration from outside sources.
