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Photo Glossary - H

Halation - diffused ring of light typically formed around small brilliant highlight areas in the subject. It is caused by light passing straight through the emulsion and being reflected back by the film base on the light sensitive layer. This records slightly out of register with the original image.

Halogens -a group of chemical elements. In photography, three of these, bromine, chlorine and iodine are used with silver to produce light sensitive material.

Half-frame - negative format of 18 x 24mm. Images are recorded on a vertical axis on standard 35mm film, thus giving 72 half-frame images on film designed for 36 exposures.

Half-frame camera - camera designed to use 35mm film in a half-frame format.

Half-plate - picture format measuring 4 ¾ x 6 ½ inches. Some early cameras produced negatives of this size.

Half-silvered mirror is a glass sheet evenly coated with a substance which transmits part of the light incident on it and reflects the remainder. Used for beam splitting devices in holography, and for front projection.

Halftone - mechanical process for printing continuous tone images in ink.

Halogens - collective term for the elements chlorine, bromine and iodine, which are combined with silver to produce the light sensitive crystals used as the basis for photographic emulsions.

Hand coloring - process of applying color tints, in the form of paint, to a photographic image to create or enhance the color effect.

Hanger - frame for holding sheet film for processing.

Hard - defines a scene, negative or print with high contrast.

Hardeners - chemicals often used with a fixing bath to strengthen the physical characteristics of an emulsion. The most common hardeners are potassium or chrome alum.

Hard gradation - term denoting the quality of harsh contrast in a photograph.

Heat filter - optical attachment made of thick infrared absorbing glass, used to absorb heat radiation from alight source without diminishing output.

Heliography - early photographic process invented by Niepce, employing a polished pewter plate coated with bitumen of Judea.

Herschel effect - the destruction of an exposed image by infrared radiation.

Hide - camouflaged barrier used by natural history and wildlife photographers.

High art photography - general term for an early form of artistic photography (1851-1870), in which photographers set out to match the style and subject matter of paintings of the period.

High contrast developer - solutions used to produce high contrast images.

High key - photograph which contains large areas of light tones, with few middle tomes or shadows.

Highlights - the brightest ares of the subject, represented on a negative by dense deposits of black metallic silver, but reproducing as bright areas on the positive print.

Hill cloud lens - lens with a 180° angle of view, used for photographing cloud formations and other meteorological work.

Holding back - 1. Shortening the development time given to film to help reduce image contrast. 2. Method of decreasing exposure given to selective areas of the print. Also referred to as dodging.

Holography - system of photography, using neither a camera not lens, in which laser beams create an interference patter recorded directly on appropriate light sensitive sheet film or plates. After processing, viewing the image by the light of a laser gives a three dimensional image.

Horizon - line at which earth and sky appear to meet. Its position, which can be altered by titling the camera or by cropping the image determines whether the sky or the landscape concentrates interest in the picture. A low horizon (tilting the camera up) concentrates interest in the sky while a high horizon (tilting the camera down) concentrates interest in the landscape.

Hot shoe - fitting on the top of many cameras designed to hold accessories, such as a flash gun.

Hot spot - often undesirable concentration of the central beam of a flood or spotlight on the subject.

Hue - name of the color (e.g. red, blue, yellow).

Hydrobromic acid - acid liberated during the developing process by the reduction of bromide.

Hydrochloric acid - chemical used in some bleaching solutions.

Hydrogen peroxide - chemical used in hypo clearing agents.

Hydroquinone - reducing agent. It is used in developers to provide high contrast results in the presence of a strong alkali.

Hyperfocal distance - distance between the camera and the hyperfocal point.

Hyperfocal point - nearest point to the camera which is considered acceptably sharp when the lens is focused on infinity. When a lens is focused on the hyperfocal point, depth of field extends from a distance halfway between this point and the camera to infinity.

Hypersensitizing - method of increasing the light sensitivity of a photographic emulsion prior to exposure.

Hypo - common name for a fixing agent, derived from an abbreviation of hyposulfite of soda, the misnomer applied to sodium thiosulfate during the 19th century.

Hypo eliminator - chemical bath which removes traces of fixing agent from an emulsion.

Photo Glossary - I

"Ideal" format - film format in the proportion of 4 to 3, e.g. 6 x 4.5cm. This ratio is considered the ideal shape by some manufacturers and many photographers for both vertical and horizontal composition.

IF (Internal Focusing) - system in which only the internal lens group shifts during focusing. IF benefits include focusing without changing the physical length of a lens body, faster focusing, reduced diameter of the focusing ring, closer minimum focusing distance, and aberrations corrected throughout the entire focusing distance range.

Illuminance - term quantifying the illumination of, or incident light falling on a surface.

Image - two dimensional representation of a real object, produced by focusing rays of light.

Image plane - plane commonly at right angles to the optical axis at which a sharp image of the subject is formed. The nearer the subject is to the camera, the greater the lens image plane distance.

Impressionism - art movement in which painters broke away from the techniques of continuous brushstrokes and clearly expressed detail. They were largely concerned with the effects of light and color.

Incident light - light falling on a surface, as opposed to reflected by it.

Incident light attachment - accessory for a hand held exposure meter which allows it to give incident light readings. Many models come with this accessory permanently attached.

Incident light reading - measurement, by light meter, of the amount of incident light falling upon a subject. The light meter is placed close to the subject, pointing towards the main light source.

Indicator chemical - neutral chemical which can be added to a sample of a solution to indicate its pH level or the presence of hypo.

Infectious development - development action which occurs in processing "lith" materials. The oxidation of hydroquinone produces new and highly active reducing agents, semiquinones, in the presence of a low quantity of sodium sulfite. This results in a very high contrast image.

Infinity - in photographic terms is a distance great enough to be unaffected by finite variations. In practice this relates to most subjects beyond 1000 meters or, in landscape terms, the horizon.

Infrared - rays that occur beyond the red end of the electro-magnetic spectrum and are invisible to the human eye. They can be recorded on specially sensitized films, producing images in black & white or color.

Infrared compensation index - used to compensate the focus for black and white infrared film. Color IR film generally does not require compensation.

Infrared focus - see IR setting.

Instamatic camera - compact camera popular in the 1960s and 70s with very simple controls, taking 126 film and yielding a 28 x28 mm negative.

Instant picture camera - camera, usually with simple controls, producing a finished photographic print within minutes of the film being exposed, (e.g. Polaroid cameras and materials).

Integral tri-pack - three emulsions, usually of different character, coated on the same film base. The system is used mainly on color materials and also on some special purpose black & white materials.

Integrating - term used to describe a method of arriving at an exposure setting by taking an average of the light readings from the bright areas and the and the shadow areas of the subject.

Intensification - chemical method of increasing the density of the photographic image. It is only suitable for treating negative materials and works better on negatives that have been underdeveloped rather than underexposed.

Intensity scale - exposure scale in which the time of exposure remains constant but the intensity of light increases in regular stops.

Interchangeable lens system - system of lenses of different focal lengths made to fit the same camera body.

Interference - interaction of light waves when they meet and either reinforce or cancel each other (e.g. holograms).

Interleaving - method of agitating more than one sheet of photographic paper in the same tray of chemicals.

Intermittency effect - states that, a number of short, separate exposures will not produce the same photographic result when combined as a single exposure of equivalent total duration.

Internegative - negative made on special color film designed for making copy prints from color slides.

Intersection of thirds - compositional technique whereby the image area is divided horizontally and vertically into equal thirds by means of four imaginary lines. The main subject is considered strongly placed it it is positioned at the intersection of any two of these lines.

Interspersed aspect ratio - basic requirement of certified photofinishers and certified photo finishing equipment. It specifies the three APS system print formats - C, H and P.

Inverse square law - states that, when the light source is a point, illumination on a surface is inversely proportional to the square of the distance of the light source.

Inverted telephoto lens - lens construction which gives a short focal length with a long back focus or lens-film distance. It enable wide-angle lenses to be produced for small format cameras, where space is required for mirrors, shutters, etc.

Iodine - chemical used in reducers and bleachers.

Iris diaphragm - continuously adjustable lens aperture consisting of interposed metal leaves.

Irradiation - by the physical structure of the emulsion and the distribution of the silver halide grains cause rays of light to be scattered as they travel through the emulsion.

IR setting - mark usually in red, found on many camera lens mounts. It indicates the focus change required for infrared photography.

IS (Image Stabilizer) - feature that minimizes the effects of camera shake. Originally designed for video cameras. Canon has transferee the technology to its EF lenses.

I setting - mark found on some cheap box cameras which indicates an instantaneous shutter speed of approximately 1/50 second.

ISO - International Standards Organization. Used instead of ASA as prefix to film speeds. The scale is identical to the ASA scale.

Ivorytype - obsolete printing process designed to give the impression of a painting on ivory. A hand colored print was impregnated with wax and squeegeed face down on hot glass. The paper base was then back by ivory tinted paper.

IX (Information Exchange) - ability of APS film to communicate with devices, and devices to communicate with film.

Photo Glossary - J

JCII - Japan Camera Inspection and Testing Institute. It is an organization in Japan to monitor export quality of Japanese made cameras.

JPEG - format for compressed graphics files. JPEG graphics are commonly used as part of World Wide Web.

Joule - unit used to quantify the light output of electronic flash. A joule is equal to one watt second of 40 lumen-seconds. The measure is used to compare flash units in terms of power output.

Photo Glossary - K

K14 - Kodak's chemical process for developing Kodachrome slides.

Kallitype - obsolete printing process, resembling the platinum process. The image is formed in metallic silver rather than expensive platinum.

Kelvin (K) - unit of measurement on the absolute temperature scale, used to describe the color content of continuous spectrum light sources.

Kerr cell - high speed shutter without moving parts, using two crossed polarizing filters at either end of a cylinder filled with nitrobenzine.

Keyed emulsion sensitivity - term used to describe the color response of color printing papers which have peak sensitivities to the three dye colors present in the same manufacturers color negatives.

Key light - studio light used to control the tonal level of the main area of the subject.

Kilowatt - unit of 1000 watts. Used to measure the power of an electrical light source.

Kinetic - concerned with movement and motion.

Knifing - method of removing marks and other blemishes from the surface of a print by gentle scraping with the tip of a sharp knife.

Kostinsky effect - development effect in which dense image points are inclined to move apart, relative to each other, and light image points to move together, relative to each other. This occurs because developer is not being equally distributed over the image point and is rapidly exhausted when to heavily exposed image points are close together.

Kromskop - early viewing instrument invented by F.E. Ives, embodying a system of mirrors and color filters to synthesize a full color image. This enabled monochrome transparencies made from separation negatives to be rear-illuminated through blue, green and red filters, and then been seen combined in register as a single image.

Photo Glossary - L

Lamp - general term used to describe the various kinds of artificial light sources used in photography.

Lamp black - pure carbon pigment, made from soot deposited from burning oils.

Lamp house - light tight housing of an enlarger or projector, which contains the light source.

Lantern slides - old term used to describe transparencies.

Large format camera - general term for any camera having a picture format of 4 x 5 inches or larger.

Laser - abbreviation for Light Amplification by Stimulated Emission of Radiation.

Latensification - method of increasing relative film speed by fogging after exposure and before development. It can be achieved by chemical or light means.

Latent image - invisible image produced by exposure which can be made visible by development.

Lateral reversal - mirror image reversal of the subject from left to right, as found in the viewfinders of some reflex cameras.

Latitude - degree by which exposure can be varied and still produce an acceptable image. The degree of latitude varies by film type. Faster films tend to have greater latitude than slower films.

LCD - liquid crystal diode. LCD is an electronic solid state display system commonly used for the face of wrist watches, and also used to display exposure information in the viewfinder of most modern day cameras. A surface can be temporarily changed from transparent to dense black by application of a charge. The LCD can be programmed to display any required black shape.

Lead acetate - crystalline, highly poisonous powder used in some toning and intensifying solutions.

Leader - beginning of a roll of film, which is attached to the camera's take up spool.

Leaf shutter - see Between the lens shutter.

LED - light emitting diode. LED is an indicator light used to convey exposure information.

Lens - optical element made of glass or plastic and capable of bending light. A lens may be constructed of single or multiple elements.

Lens barrel - metal or plastic tube with a blackened inner surface, in which the lens elements and mechanical components of the lens are mounted.

Lens cap - plastic, rubber or metal cover which fits over the front or back of the lens to protect it.

Lens coating - layer or multiple layers of thin anti-reflective materials applied to the surface of lens elements to reduce light reflection and increase the amount of transmitted light.

Lens drive system - used in autofocus SLR cameras. One type has a motor located inside the lens; in another, a motor inside the camera body turns the lens via a drive shaft.

Lens hood - opaque tube, either cylindrical, square of funnel shaped, use to shield a lens from stray light outside the field of view.

Lens shade - see Lens hood.

Lens shutter camera - camera with the shutter built into the lens.

Lens speed - largest lens opening (smallest f-number) at which a lens can be set. A fast lens transmits more light and has a larger opening than a slow lens. Determined by the maximum aperture of the lens in relation to its focal length. The speed of a lens is relative to it's focal length. A 400 mm lens with a maximum aperture of f/3.5 is considered extremely fast, while a 28mm f/3.5 lens is thought to be relatively slow.

Lens system - describes the type and quantity of lenses available for use with a particular camera.

Lenticular screen - lens system consisting of a screen containing a number of small lenses.There are two applications of lenticular systems. They are used in some exposure meters to gather light and to determine the angle of acceptance of light by the meter. A lenticular screen consisting of a number of lenses et into rows can be used at the camera stage to produce stereoscopic images by synthesizing binocular vision.

Light - visible radiated energy which forms part of the electro-magnetic spectrum in the wavelength range of 4000-7000 Å (400-720 nm).

Lightbox - box of fluorescent tubes balanced for white light and covered with translucent glass or plastic. Used for viewing, registering or correcting film negatives and positives.

Lighting ratio - ratio of the brightness of light falling on the subject from the main (key) light and other (fill) lights. A ratio of about 3:1 is normal for color photography.

Light meter - alternate term for exposure meter.

Light sources - general term applied to any source of light used in photography.

Light tent - tent like structure made of translucent material hung around a frame. The fabric diffuses the light coming from outside the tent so that highly reflective subjects placed inside the tent can be photographed without reflections.

Light-tight - term denoting a material or piece of equipment that is impervious to light.

Light trail - image track recorded on photographic material when a point of light is shifted during exposure.

Light trap - system of entry to a darkroom which allows easy access, but prevents unwanted light from entering.

Light value - alternative term for exposure value (EV).

Limiting aperture - actual size of the aperture formed by the iris diaphragm at any setting.

Linear perspective - apparent convergence of parallel lines with increasing distance in a two dimensional image.

Line film - high contrast film which, after correct development, gives negatives of black and white only (with no grays).

Line image - photographic image consisting of black areas and clear film i.e. white.

Linked Ring Brotherhood - group of pictorialist photographers who broke away from the Photographic Society of Great Britain. Existed between 1892-1910.

Lippman process - early color process invented by Professor Gabriel Lippmann (1845-1921). Light first passed through an almost transparent emulsion layer and was then reflected back by a layer of mercury. The interference between reflected and incident light produced a latent image in the emulsion which could be given b&w processing, but when backed with a mirror appeared in color.

Lith film - extreme form of line film, which produces very high contrast images when used in conjunction with a special lith developer.

Local control - method of controlling the final quality of a print by increasing or decreasing the exposure given to localized areas of the print by selective masking.

Log e - logarithmic value (to the base 10) of the relative brightness exposed on the film when undergoing sensitometric testing.

Long focus - a lens in which the focal length is much greater than the diagonal of the film format with which it is used.

Low key - photograph in which tones are predominantly dark and there are few highlights.

Lumen - unit of light intensity falling onto a surface.

Lumen second - unit to measure the total light output of a photographic source.

Luminance - measurable amount of light which is emitted by or reflected from a source.

Luminance meter - alternate term for exposure meter.

Luminescence - visible light produced from a surface submitted to invisible radiation such as UV, X rays and son on. Unlike fluorescent light it continues to be emitted after the existing source is removed, gradually fading away.

Luminosity - brightness of either a light source or a reflective surface.

Luminous flux - intensity of a light source, measured in lumens.

Photo Glossary M-O to page top Photo Glossary E-G

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