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Photo Glossary - C

•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.

Carbro process - early color print process using an adaptation of the carbon printing process.

•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.

Chlorhydroquinone - developing agent contained in warm tone developers.

•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 - soluble gun-cotton, dissolved in a mixture of ether and alcohol.

•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.

Composition - visual arrangement of all the elements in a photograph.

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.

Convex lens - simple lens which causes rays of light from a subject to converge and form an image.

•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.

Cut film - negative film available in flat sheets. The most common sizes are 4x5, and 8x10 inches.

•Cyan - blue-green subtractive primary color which absorbs red and transmits blue-green.

Cyanotype - contact printing process producing a blue image on a white background.

Photo Glossary - D

•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 - Deutsche Industrie Norm (German Standards Organization).

•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.

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