Police Photography Definition of Terms
Actinic rays - light rays of short wavelengths occurring in the violet and ultraviolet parts of the spectrum, which produce chemical changes, as in photography.
Angle of incidence - the angle of incidence as used here conforms to that used in optics to describe reflection and refraction of light rays.The angle is measured with respect to the normal to the surface, rather than to the surface itself. The normal is an imaginary line perpendicular (90°) to the plane of the surface. Thus, a straight-on impact (along the normal) is said to have an angle of incidence of zero.
Aperture - Adjustable opening, also referred to as f-stop, that controls the amount of light that is focused on the film.
Aperture preference - Term used to describe the automatic exposure system used on some cameras, in which a specific aperture is selected but the shutter speed adjusts automatically to expose the film to the correct amount of light.
Artificial light - Any light other than daylight.
Artificial light film - Color film balanced for use in tungsten artificial light, usually of 3200°K. Packs are usually marked tungsten or Type B.
ASA - American Standard Association, formerly a standardized rating number for film based on its sensitivity to light.
Auto iris - Automatically regulates the amount of light entering the camera.
Auto white balance - Electronically adjusts camera color levels.
Auto focus - Automatically sets the focus (distance) from scene to camera.
Automatic camera - A camera with a built-in exposure meter that automatically adjusts the lens opening, shutter speed, or both for proper exposure.
Auxiliary lens - A lens element added to a regular lens to shorten or increase the focal length.
Background - The part of the scene that appears behind the principal subject of the picture.
Backlighting - Light shining on the subject from the direction opposite the camera; distinguished from frontlighting and sidelighting.
Backscatter - The light reflected back to the camera in underwater photography caused by flash reflection of particles suspended in the water.
Blur - Indistinct image caused by movement or inaccurate focusing.
Bounce lighting - A light source reflected off of another surface and then onto the subject.Flash or tungsten light bounced off the ceiling or walls in order to give the effect of natural or available light.
Bulb - A shutter speed setting used to hold the shutter open for extended periods with the use of a shutter release cord or continuous pressure on the shutter release button.
Cable release - A flexible, enclosed wire used to release the shutter mechanism.
Camera - A photographic apparatus used to expose sensitized film or plates to reflected light images formed by a lens. Also, an electronic device to change film or live action into video signals.
Camera angle - The photographer’s point of view of a subject or scene as viewed through the lens or viewfinder.
Cartridge - A lightproof container that is loaded with film in the dark and can be handled and placed in the camera in the light.
Cassette - A film cartridge or magazine. A lightproof holder used in autoradiography for exposing x-ray film to radioactive blots.
Circle of confusion - An optical term describing the size of an image point formed by a lens.
Close-up - A photograph taken close to the subject or evidence, often requiring an auxiliary lens. Macro and micro are degrees of close-up.
Color - The sensation produced in the eye by a particular wavelength or group of wavelengths of visible light.
Color balance - The ability of a film to reproduce the colors of a scene. Color films are balanced in manufacture for exposure to light of a certain color quality daylight, tungsten, etc. Color balance also refers to the reproduction of colors in color prints, which can be altered during the printing process.
Color balancing filter - Filters used to balance color film with the color temperature of the light source and to prevent the formation of colorcasts. An 85B filter is used with tungsten film in daylight, an 80A filter with daylight film in tungsten light.
Color compensating (CC) filters - Comparatively weak color filters used to correct for small differences between the color temperature of the illumination and that for which the film was manufactured.
Color conversion filters - Fairly strong color filters used for exposing film in light of a type markedly different from that for which the film was made.
Color negative film - Film that records the colors of the subject in complementary hues that are subsequently reversed again in the printing paper to give the correct colors.
Color reversing film - Film that produces a direct positive by effectively reversing the negative image during processing. Transparency (slide) film is of this type.
Contrast - The difference in intensities of light falling on various parts of a subject. The density range of a negative, print, or slide; the brightness range of a subject or the scene lighting.
Contrast filter - A colored filter used to make a colored subject stand out either lighter or darker (for black-and-white film).
Correction filter - Filters used to alter colors to suit the color response of the film.
Coupled exposure meter - Exposure meter built into the camera and linked with the aperture or shutter speed controls, or both.
Coupled rangefinder - A rangefinder connected to the focusing mechanism of the lens, which is focused while measuring the distance to the subject or object.
Cropping - The elimination of part of an original image on a single negative during printing either because of automation or enlargement.
Daylight color film - Color film designed to be used with daylight or a light source of equivalent color temperature, including blue flashbulbs and electronic flash. The film is balanced to 5400 EK.
Dense - Dark negative or positive film on paper that is overexposed, overdeveloped, or both.
Depth of field - The zone between the foreground and background that appears in sharpest focus for a particular lens, distance, and aperture.
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.
Developer - A solution used to turn the latent image into a visible image on exposed films or photographic papers.
Electronic flash - Lighting unit utilizing the flash of light produced by discharging a current between two electrodes in a gas-filled tube. _
Electronic viewfinder (EVF) - A small TV monitor attached to a video camera for viewing of recorded images.
Emulsion - a suspension of a salt of silver in gelatin or collodion used to coat film.
Existing light - That light present at any one time in a given area no matter what the source.
Exposure index - Methods of rating film speed developed by the American Standards Association (ASA), now known as the American National Standards Institute, Inc. (ANSI).
Exposure setting - The lens opening and shutter speed selected to expose the film.
Extension tube - Increases the distance between the lens and the sensitive film in the camera and changes the lens capability.
Eyepiece - The optic found on a camera, microscope, telescope, and so on, used to look through the instrument.
Fade-in/Fade-out - Gradually changing video from dark to picture or picture to dark.
Fast film - Film that has an emulsion that is very sensitive to light. Such films have high ASA ratings.
Fast lens - lens with a large aperture, requiring less light.
Field of vision - The area a person is able to see through the viewfinder, scope, or lens.
Fill-in - Secondary illumination to keep shadow areas from photographing too dark; also known as the fill light.
Film - A sheet or strip of celluloid coated with light-sensitive emulsion for exposure in a camera.
Film plane - That portion of the camera body that holds the sensitized film in place during the exposure process. It is also that position of the camera where the image is focused.
Film speed - A means of representing numerically the response of a photographic emulsion to light.
Finder - A viewer through which the picture to be taken may be seen and centered.
Fish-eye lens - Wide-angle lens with angle of view that may reach 180°. Depth of field is practically infinite.
Flash - A general term for any auxiliary, sudden, brilliant light. A unit holding flashbulbs is referred to as a flash.
Flash sensor - Electronic unit actuated by light flash.
Flood - Light source providing a wide, diffused beam of light.
Fluorescence - Property possessed by various substances that glow when exposed to light of a short wavelength. The phenomenon in which some substances absorb light and re-emit part of it as light of a longer wavelength. Fluorescence ceases when incident or exciting illumination ceases.
Focal length - The distance in millimeters (mm) from the center of the lens to the point where the image comes into critical view.
Focal plane shutter - A shutter that operates immediately in front of the focal plane. Usually contains a fixed or variable-sized slit in a curtain of cloth or metal that travels across the film to make the exposure.
Focus - Point at which converging rays of light from a lens meet.
Focusing - The adjustment of the lens-to-film distance to produce a sharp image of the subject.
Format - Size, shape, and general makeup of negatives, slides, photographic prints, camera viewing areas, or video equipment.
Frame - An individual picture on a roll of film or one full onscreen image of displayed computerized information.
Frame buffer - A separate area of memory where an image or frame is stored in a computer.
Frame counter - A dial on the camera indicating the number of exposures or frames used.
f-stop (f-number) - Focal setting for the diaphragm controlling the size of the aperture; the higher the f-stop, the smaller the aperture opening.
Fully automatic - Term indicates that camera aperture and speed settings can be combined to give complete automatic exposure for a picture.
Gain select - Increase sensitivity to light. Used when sufficient illumination is not available for video recording.
Gamma - A process that improves the video image by correcting for the lack of picture clarity.
Glare - Intense light reflected off highly reflective surfaces such as water, glass, and very light-toned objects.
Grain - Individual silver particles or groups of particles in the emulsion
which, when enlarged, become noticeable and sometimes objectionable.
Graininess - The grainy appearance of photographic enlargements. More prominent on higher-speed film. The sand-like or granular appearance of a negative, print, or slide resulting from the clumping of silver grains during development of the film. Graininess becomes more pronounced with faster film, increased density in the negative, and degree of enlargement.
Guide number - An indication of the power of a flash unit, enabling the correct aperture to be selected at a given distance between flash and subject. The number divided by the distance gives the f-stop that should be used. A film speed is specified with the guide number and recalculation is needed for different speeds.
Haze filter - Lens filter that reduces the effect of atmospheric haze. Red reduces most, green the least. A blue filter induces haze. _
Illumination - A specific amount of light present in any given area. Expressed in lux or foot-candles; the lower the lux of equipment, the less light required for a good picture.
Image - The photographic representation of an object or scene formed by optical or chemical action.
Image aspect ratio - Ratio of the width to the height of a displayed computer generated image.
Image resolution - Number of pixels displayed per unit of printed length in an image, usually measured in pixels per inch (ppi).
Infrared photography - Recording of images produced by infrared radiation.
Iris - The opening of a camera lens that controls the amount of light let in.
Lens cap - A cover used to protect a lens from dust and damage when not in use.
Lumen - Photometric unit equal to the luminous flux on 1 ft2 of
surface from a standard candle 1 ft away.
Luster - The gloss or shine possessed by a fiber, resulting from its reflection of light. The luster of manufactured fibers is often modified by use of a delustering pigment.
_Macro lens - Lens designed to work at close distance, permitting image
Macro photography - Photography usually involving close-up capabilities,whether with lens or bellows, with a magnification from life size (110) up to 50 times (501).
Magenta - A reddish-blue (minus green) color.
Micro photography - The term used in Europe for the making of large photographs of small objects, usually through a microscope. In the United Kingdom and the United States this is called photomicrography, and microphotography is used to refer to the technique of making microscopically small photographs by the process of optical reduction.
Monochrome - Single colored; for instance, black-and-white photographs and sepia- or other-toned images in one color. Similar light rays of one color wavelength (i.e., a single, pure color).
Motor drive- Device for advancing the film and retensioning the shutter by means of an electric motor.
Multiple flash - The use of more than one flash unit, usually operating
Natural size - A photograph enlarged to the true size of the content.
Near point - The closet object to the camera in focus for a given distance.
Negative - Photographic image in which the amount of silver present is more or less based on the reflectivity from the original object. Black is white, white is black. The developed film that contains a reversed-tone image of the original scene.
Normal lens - A lens that makes the image in a photograph appear in a perspective similar to that of the original scene.
Objective - The first lens, lens system, or mirror through which light passes or from which it is reflected in an optical system.
Open flash - Method of using the flash in which the shutter is opened, the flash is fired, and then the shutter is closed. It is used when the shutter speed is unimportant because existing lighting is poor or nonexistent.
Open up - The term used in reference to changing to a larger aperture (f-stop) opening.
Optical microscope - An instrument used to obtain an enlarged image of a small object, utilizing visible light; in general, it consists of a light source, a condenser, an objective lens, and an ocular or eyepiece that can be replaced by a recording device. Also known as a light microscope.
Pan-and-tilt head - Tripod head with separate locks for horizontal (pan) and vertical (tilt) movements of the camera.
Panning - The movement from left to right and right to left of the camera; normally associated with movie and video cameras.
Parallax - Difference between the image seen in a viewfinder and that
recorded by the taking lens. Most pronounced at close distance with twin-lens reflex and rangefinder cameras. Single-lens reflex and studio cameras are free from parallax error.
Peak - The visual image representing an allele on an electropherogram.
Photo flash lamp - An electronic lamp working at higher than the normal voltage,giving brighter light.
Photoelectric cell - Light-sensitive cell used in exposure meters and for remote triggering of the shutter.
Photoflood - Photographic lamp designed to produce a high output of light during a comparatively short life.
Photogrammetry - The process of surveying or mapping through analysis of photographs. A scientific method used to determine from photographs the length of skid marks, width of roadways, or any other types of measurements needed.
Photographic negative - A transparency produced when black-and-white film is exposed in a camera and then developed. The term is derived from the appearance of the transparency, in which white areas of the original appear the darkest or most opaque, while the darkest portions of the original are almost clear. With color film the light–dark reversal is coupled with a change of colors to the complements of those in the original material.
Photographic positive - A print made by passing light through the negative generally onto photographic paper. In this print the tonal values are directly proportional to those of the original; i.e., light areas of the original appear light, and the dark areas are dark.
Photography - To write or draw with light. Recording with light is closer to the modern meaning of the word.
Photomicrographs - Photographs that are made through a compound microscope and may be a greatly enlarged image of a small area. Similarly, enlarged photographs, which may be prepared with only a lens of very short focal length, are accurately termed photomacrographs. It is extremely difficult to distinguish between photographs made by these two processes, and both are often incorrectly referred to as a photomicrograph.
Projected prints - A print made by focusing light from the negative on the printing paper by means of a lens system. These positives are generally enlargements. Some workers refer to them as bromides because of the type of paper emulsion originally used.
_Quartz lens - A special lens used for ultraviolet photography.
Rangefinder - A viewer system found on cameras without a through-the-lens viewing capacity (SLR cameras).
Record/review - Automatically rewinds and plays back the last few seconds of videotape recording. Provides a smooth transition from one segment to another.
Reflection - The bouncing back of rays of light striking a surface.
Reflex camera - A camera in which the image can be seen right side up and full size on the ground-glass focusing screen.
Refraction - The bending of a light ray when passing obliquely from one medium to a medium of different density.
Refractive index (N) - The change in direction (apparent bending) of a light ray passing from one medium to another of different density, as from air to water or glass. The ratio of the sine of the angle of incidence to the sine of the angle of refraction is the index of refraction of the second medium. Index of refraction of a substance may also be expressed as the ratio of the velocity of light in a vacuum to its velocity in the substance.
Resolution - The capability of an optical device to separate into
two or more objects (or points) what to the unaided eye appears to be one object (or point), thus yielding details not otherwise perceptible. Measurement in units per inch of the amount of detail in an image file: dpi = dots per inch; ppi = pixels per inch; lpi = liners per inch.
Reversal - A positive film such as slide film (either color or black-and-white).
Rogues’ gallery - A file of photographs of arrested individuals; usually includes fullface and profile photographs (mug shots) along with detailed physical description, age and place of birth, Social Security number, fingerprint classification, nicknames and aliases, modus operandi, etc. (also called mug shot file).
Scale - The enlargement or reduction of an object or texture.
Schlieren optics - Imaging system in which the transparent or translucent object to be examined is placed between two spherical mirrors. The illuminant is a point light source placed at the focal point of one of the mirrors. Parallel light rays from the mirror pass through the object to the second mirror, which projects the image onto a screen. A knife edge is placed at the focal point of the second mirror to block unrefracted light rays. Only light rays refracted by the object reach the screen.Schlieren optics can produce images of thickness, density, and refractive index differences.
Self-timer - A timing device permitting the photographer to delay shutter.
Shoot (shot) - A slang term for taking or having taken a photograph.
Shot sheet - A form for recording all pertinent photographic information on a particular roll of film.
Shutter - Mechanical device that regulates the time light can act upon the film.
Shutter preference - An automatic exposure system in which shutter speed may be selected and the aperture is adjusted automatically to give correct exposure.
Shutter speed - The action of the shutter that controls the duration of an exposure.The faster the speed, the shorter the exposure.
Silhouette - A photograph that shows only the mass of a subject in black against a white or colored background.
Single-lens reflex - Camera system utilizing a hinged mirror between the lens and the film that swings out of the light path when the shutter is open, allowing the taking and viewing functions of a lens to be combined.
Slide - A positive film mounted in a slide mount or a positive print on glass for projection upon a screen.
Slide film - Direct reversal film; usually color film used in cameras for full-color projection positives. Sometimes called color transparency film.
Slit-width - Size of the opening of the slit through which light emerges. Size depends on wavelength range, separation ability of wavelength selector,and desired isolation of specific wavelength.
Slow film - Film having an emulsion with low sensitivity to light. Typically such films have an ASA rating of 32 or less.
Slow lens - A lens with a relatively small maximum apertura, such as f-8.
Snapshot - A casual picture taken by amateurs, usually with simple equipment.
Snow Print Wax - Registered name of an aerosol product used to assist in the photography and casting of footwear impressions in snow.
Speed - The sensitivity of a photographic emulsion to light. ISO, ASA, or DIN numbers indicate their relative speed characteristics. The higher the number, the faster the film reacts to light.
Spotlight - Lamp unit with a reflector and lens that can either focus light into a small, concentrated circle or give a wider beam.
Standard lens - Lens whose focal length is approximately equal to the diagonal of the film format with which it is used. It is also referred to as the prime or normal lens.
Static streak- Light streak that appears on photographic film, usually in cold weather when film is advanced too quickly. Static streaks can be harmful to development of clear photographic images.
Still - A photograph lacking motion; a single frame.
Stop - A lens aperture or diaphragm opening, such as f-4 and f-5.6.
Strobe - Electronic flash unit. An electrical power supply charges the gas-filled flash tube emitting light between 1/1000 sec and 1/50,000 sec. A strobe can be manual or manual and automatic.
Surveillance photography - A secretive, continuous, and sometimes periodic visual documentation of activities involving persons, places, or objects of importance to an investigation.
Sync-cord - An electrical power cord used to connect the flash unit to a power source.
Synchroflash - A term applied to flash photography in which a flash bulb is ignited at the same instant that the shutter is opened.
Time exposure - The camera shutter is opened and closed manually, not automatically.
Time-lapse - A timing device that can be set to take a photograph every few seconds, minutes, hours, etc.
Transmission - The ratio of the light passed through an object to the light falling upon it.
Transmitted light - Light that is passed through a transparent or translucent medium.
Transparency - A positive photographic image on film, viewed or projected by transmitted light (light shining through film).
Trash mark - Mark left on a finished copy during photocopying; results from imperfections or dirt on the cover glass, cover sheet, drum, or camera lens of a photocopy machine.
Tripod - A three-legged stand used to support a camera or lens and camera.
Tungsten light - Incandescent light, from a bulb having filaments usually of lower wattage, 15 to 500 W.
Tungsten light film - Color film balanced to suit tungsten light sources, with a color temperature of 3200°K.
Twin-lens reflex (TLR) - Camera having two lenses of the same focal length; one is used for viewing and focusing, the other for exposing the film. The lenses are mounted above each other.
Ultraviolet filter - A filter that transmits ultraviolet light as used for photography by the reflected ultraviolet light method.
Ultraviolet light - Light rays beyond the visible spectrum of light at its violet end with wavelengths longer than x-rays, but shorter than visible light.
Ultraviolet photograph - Any photograph that records the document under ultraviolet illumination. With some of these the ultraviolet radiation strikes the film, but with others a filter is employed so that only the visual fluorescence caused by the ultraviolet is recorded.
Underexposure - Results of insufficient light exposing the film. A condition in which too little light reaches the film producing a thin negative, a dark slide, or a muddy-looking print.
Unipod - A one legged support for a camera.
Videography - The recording of visual images electronically on magnetic tape.Usually accompanied by a recorded soundtrack.
Viewfinder - A viewing instrument attached to a camera that is used to obtain proper composition.
Washed out - A negative or print lacking detail and contrast.
White balance - A procedure used to tune a video camera’s color by setting it to perfectly reproduce a white object.
Zoom lens - A lens with the capacity to have varied focal lengths while maintaining focus on a particular subject at a given distance.
Zooming - Moving a variable focus lens during an exposure.
Related Readings: Police Photography
1. Police Photography Review Notes
2. Police Photography Reviewer 1