93 terms

Certified Professional Photography Glossary

CPP Glossary Terms. Definitions are from The Focal Encyclopedia of Photography (3rd Edition) and Photography by London, Stone and Upton (10th and 11th edition).
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Aliasing
Low and medium resolution computer imaging systems display normally smooth edges as jagged edges. These jaggies are known as aliasing. It may result from undersampling the spatial frequency, or when the detail exceeds the display ability of the monitor.
Ambient Light
The light that already exists where a photograph is to be made, as opposed to light brought in by the photographer. Often implies a relatively dim light. Also called ambient light or exisiting light.
Angle of View
Angle subtended at the center of the entrance pupil of the lens by the subject field or area delineated by the image format of the camera. Generally, the value for the diagonal extent is quoted, this being the largest for the horizontal, vertical, and diagonal dimensions of a rectangular or square format. For an aberration-free lens of focal length "f" and format dimension "k", the corresponding angle of view "W" is given by W= 2 tan -1 (k/2f). It normally is equal to the corresponding angle subtended at the format by the emergent rays, except in the case of lenses that have pincushion or barrel distortion, such as fisheye types.
Aperture
The size of the lens opening through which light passes.
Aperture Priority
A mode of automatic exposure in which the photographer selects the aperture and the camera sets the shutter speed that will produce the correct exposure.
Aspect Ratio
The width to height proportions of an image format, commonly used in motion picture photography and video. The aspect ratio for conventional motion pictures is 1.33 to 1, but wide-screen aspect ratios range from 1.8 to 1 to 3 to 1.
Available Light
The light that already exists where a photograph is to be made, as opposed to light brought in by the photographer. Often implies a relatively dim light.
Barn Doors
Opaque flaps attached to the edges of a light and used to control light spread, for shading effects in the set, and to keep flare-causing light from entering the camera. Two, with one on each side, or four with additional top and bottom flaps, are typically used. The flaps are hinged and blackened so the light spread can be continuously restricted. An open-face fixture may cast a double-edged shadow, one from the lamp and a less-distinct one from the reflector.
Barrel Distortion
A lens aberration or defect that causes straight lines to bow outward, away from the center of the image.
Bit
The smallest unit of information useable by a computer, indicated by a 1, or a 0, describing one of two conditions- on or off.
Broad Lighting
Portrait lighting in which the main light illuminates the side of the face turned toward the camera.
Butterfly Lighting
Portrait lighting in which the main source of light is placed high and directly in front of the face.
Byte
A unit of digital data containing 8 bits.
Calibration
To adjust the output of a digital device, such as a computer monitor, to match a predefined standard.
Chromatic Aberration
A lens defect that bends light rays of different colors at different angles and therefore focuses them on different planes.
Color Balance
1. A film's or a sensor's response to the colors of a scene. 2. The reproduction of colors in a color print, alternatable during image editing or darkroom color printing.
Color Space
Three-dimensional representation of colors.
Color Temperature
A numerical description of the color of light measured in degrees Kelvin (K).
Colorimeter
An instrument for measuring colors. Visual colorimeters are sometimes used in research work, but practical colorimetry is usually carried out with photoelectric instruments in which the light from the sample is passed through three filters onto a photoelectric detector.
Compression
A means of reducing the file size for a digital image in order to reduce storage requirements or transmission speed across networks.
Continuous Tone
Describes an image with a smooth gradation of tones from black through grays or colors to white.
Contrast
The difference in darkness or density between one tone and another.
Cookie
A thin opaque sheet with a pattern of irregularly shaped and positioned holes. When held in front of a light source, a dappled highlight and shadow pattern is cast on a backdrop or other surface. Typically used so that light appears to have been filtered through trees outside a window. The edges of the cookie should be irregular, and not straight-edged, to avoid angular shadows that revel the use of an effect tool.
Depth of Field
The area between the nearest and farthest points from the camera that are acceptably sharp in an image.
Diffusion
Scattered, not all coming from the same direction. For example, sunlight on a cloudy day.
DPI
Dots per inch: a measure of the resolution of a digital printer or photomechanical halftone. The number of dots or points that can be printed or displayed by a device.
DSLR
Digital Single-Lens Reflex
Dynamic Range
The difference between the lightest and darkest (or highest and lowest) values in a scene or image. Sometimes, in the zone system, called subject brightness range.
Environmental portraiture
Kind of portraiture in which the loose composition of an image provides information about where the subject lives and the conditions it survives in.
Exposure
1. The act of letting light fall on a light-sensitive material. 2. The amount of light reaching the light-sensitive material;specifically, the intensity of light multiplied by the length of time it falls on the material.
Feathering
To take advantage of the unequal distribution of light by most lighting equipment. In particular, to aim a light in front of the subject so the light falls off toward the side of the head. Also, to achieve even illumination by directing the brighter center portion of the beam of light at the more distant part of a scene while the less intense edge of the beam illuminates the closer part.
Fill Light
A source of illumination that lightens shadows cast by the main light and thereby reduces the contrast in a photograph.
Flag
An oblong opaque light blocking device that shades a subject area or the camera lens. When attached to an articulated arm for each of positioning, it is sometimes called a French Flag.
Flat Lighting
Lighting that comes primarily from the direction of the camera, often used synonymously with front lighting. Flat lighting completely illuminates the front of the subject. Pictures lit in this manner show little, if any , depth because the entire visable part of the subject is uniformly illuminated , and few if any shadows exist to delineate surface detail and form.
Focal Length
The distance from the lens to the focal plane when the lens is focused on infinity. The longer the focal length, the greater the magnification of the image.
Gamma
A number that describes the rate at which tones or values change. A higher gamma is the same as a higher contrast.
Gel
1. The jelly produced when an emulsoid sol coagulates or sets. 2. A filter made from a thin dyed sheet of gelatin.
Gigabyte
(GB) 1,000,000,000 bytes. Used to describe the size of computer memory or storage.
Gobo
A small opaque panel, typically mounted on a boom stand, that is used to shade the light from an area of a subject or to shade a camera lens from direct light that could cause undesirable flare.
Gradation
A more or less gradual change of tone, color, texture, etc. between adjacent areas of an object or the corresponding image. Gradation provides the viewer with information concerning the three-dimensional attributes of the subject, such as the facial features of a portrait subject as revealed by the variation of tones produced by the lighting.
Gray Scale
1. A means of rendering a digital image in black, white, and gray tones only. 2. A format or color space for describing such an image.
Guide Number
A number used to calculate the f-setting (aperture) that correctly exposes a film or sensor of a given sensitivity (ISO speed) when the film or sensor is used with a specific flash unit at various distances from flash to subject. To find the f-setting, divide the guide number by the distance.
Hair Light
A light used to produce a highlight that separates dark hair from a dark background. With blonds, a hair light can brighten up a picture and make it less somber. Hair lights are often placed behind the subject on the side opposite the main light.
High- Key
Describes an image composed of mainly light tones. Although exposure and lightng influence the effect, an inherently light-toned subject is almost essential. High key photographs usually have pure or nearly pure white backgrounds. In the studio this usually requires more light on the background than is common for moods other than high key. The high-key effect requires tonal gradation or shadows for modeling, but precludes extremely dark shadows. Unless the main light is very close to the camera, enough fill to maintain a lighting ratio no greater than 3:1 is usually necessary to maintain the high-key mode.
Histogram
A graph that shows the distribution in a digital image of tones (from white, through shades of gray, to black) or of colors.
Honeycomb
A panel of hexagonal cells used to restrict lateral light spreading when placed over a light source and reflector. The degree of restriction depends on the size and depth of the cells, on their color from white to black, and on the type of fixture over which they are used. Photographers often select them according to the type of edge shadow they wish to produce, hard-edged or graduated. A black grid over a small open-faced fixture will project a harder edge shadow than a white grid over a large fixture with a front diffuser. Honeycomb grids do not increase contrast since they do not change the size of the source., but limiting light spread can effectively increase contrast and color saturation by removing fill light and reducing flare.
Hue
Attribute of a visual sensation according to which an area appears to be similar to one, or to proportions of two, of the percieved colors, red, yellow, green, and blue. Hue varies with the wavelength composition of the light. The other two attributes of light are lightness (or brightness) and saturation (or chroma).
Image Processing
The alteration, enhancement, and analysis of images for the purpose of improving the pictorial representation or extracting data from the image. Image processing relies on a number of well-tried algorithms that simplify and spread the process. While image processing is applicable to optical and analog approaches, the term's use is mostly limited to digital imagery.
Incident Light
Light that is falling on a subject, particularly as applied to exposure-meter readings. An incident light exposure meter determines exposure by measuring the illuminance or light falling on the subject and assuming average reflectivity.
Inkjet
A digital printer that sprays microscopic droplets of ink onto a receptive surface to create the apperance of a continuous-tone photograph.
Inverse Square Law
A law of physics stating that the intensity of illumination is inversely proportional to the square of the distance between light and subject. This means that if the distance between light and subject is doubled, the light reaching the subject will be only one-quarter of the original illumination.
ISO
A numerical rating that describes the sensitivity to light of film or of a digital camera's sensor. The ISO rating doubles as the sensitivity to light doubles.
Kelvin
Unit in which description of the color of light is measured.
Kicker
A light source used to produce a highlight in addition to that caused by the main light. Highlights produced by kickers are usually small. If the kicker highlight occurs inside the larger main-light highlight, there is an illusion of brilliance that could not be produced by the main light alone without overexposure of the subject. Placement of the kicker is usually to the rear of the subject. This is partly to keep the kicker from illuminating too large an area of the subject. Such an angle is also likely to produce some direct reflection that, because of its brightness, makes a kicker of greater immensity unnecessary.
Main Light
The principle source of light in a photograph, particularly in a studio setup, casting the dominant shadows and defining the texture and volume of the subject. Also called key light.
Mixed Color Lighting
Occurs when light from different sources blend together to produce a color balance different from that of any of the light sources used, but a color balance that is uniform throughout the scene. In most scenes, mixed color lighting can be corrected to a photographic standard color balance by filters over the lens.
Moiré
An artifact of an imaging system resulting from interference between two regularly spaced sets of lines. In printing, moiré occurs because of incorrect printing angles for lines screens; in video, moiré occurs when strong verticals are scanned.
Overexposure
To give more than normal exposure to film, paper, or a digital capture.
Painting with Light
Moving the light source during a long exposure. This technique can achieve effects difficult or impossible with a fixed source. Moving the source over a wide area enables a small light source to produce a shadow pattern similar to that of a large soft source. Some fiber optic light sources are designed specifically for painting with light. These confine the beam well enough to allow placing the light within a couple of centimeters of the subject without recording the hand of the photographer or the source itself on film. This permits creating highlights similar to those of a larger source farther from the subject, but from angles of illumination impossible for the larger source. Such highlights may have the brightness of those produced by direct reflection, but with the color saturation of those produced by diffuse reflection. The disadvantage of painting with light is the impossibility of seeing the effect before processing the film. Polaroid testing and experience are essential ; conveniently available conventional film processing is highly desirable.
Parallax
The difference in point of view that occurs when the lens (or other device) through which the eye views a scene is separate from the lens that exposes the image.
Photosites
Small electrodes located on the image sensor of a digital camera which absorb photons.
Pixel
Short for picture element. Digital images are composed of many individual pixels, each having a specific color or tone that can be displayed, changed, or stored. When the pixels are small enough, the eye merges the individual pixels into continuous tones.
Pixellation
When the spatial resolution of an electronic, computerized image is low, the individual pixels, or groups of pixels become visible. This blockiness is known as pixellation. The degree of visability of these blocky pixels depends on the viewing distance from the canthode-ray tube (CRT)
Polarizer
In photography, a filter that transmits only light that is polarized in a particular direction, depending on the type and orientation of the filter. For example, if nonpolarized light is incident on a linear polarizer, only light polarized parallel to the polarization axis of the filter will be transmitted.
PPI
Pixels per inch, a measure of the resolution of a computer display, digital camera, or digital image.
Primary Colors
Basic colors from which all other colors can be mixed.
RAM
Random access memory. RAM Chips are composed of intergrated circuits acting as temporary data storage within a computer or other device to allow rapid data access and processing.
Range Finder
An optical device that assesses object distance based on comparing images from two different view points.
Ratio
The result of dividing the larger number of a pair of data by the smaller. For example, the lighting ratio on the face of a person sitting for a portrait may be 3 to 1, meaning that one side of the face receives three times as much light as the other.
Reflected Light Meters
An exposure meter that measures the amount of light reflected or emitted by a subject. Sometimes called a luminance meter.
Reflectors
1. A reflective surface, such as a piece of white cardboard, that can be positioned to redirect light, especially into shadow areas. 2. A reflective surface, often bowl shaped, that is placed behind a lamp to direct more light from the lamp toward the subject.
Render
In electronic imaging, the application of a textured surface to a wire frame object in a computer graphic. Rendering can be accomplished in two-and three-dimensional animation programs. In either case, the computer power required to do rendering quickly and accurately is substantial.
Resolution
The ability to differentiate fine detail, for example, one measure of the quality of a lens. 2. the fineness of detail or the amount of data available to represent detail in a given area. In a digital image file or on a computer monitor, resolution refers to the number of pixels in a linear inch (PPI); on a printer, to the number of dots printed in a linear inch (DPI); on a scanner, to the number of samples saved for a given area of the scanned image (SPI).
RGB
Red, green, blue, the primary colors of light used in digital imaging that, when combined, can create a full-color image on a computer monitor. Also refers to the way most digital color images are described in image-editing software.
Saturation
The extent to which a color deviates from neutral, corresponding to chroma in the Munsell color system and purity in colorimetry.
Schiempflug Effect
An inclined subject plane is rendered sharp when the plane of the subject, the rear nodal (principal) plane of the lens and the film plane, all extended into space as necessary, meet in a common line. The depth of the field about the subject line is inclined in the same direction as the plane.
Scrim
A sheet of gauze or other translucent material that is used between a light source and a subject to diffuse the light, as for a closeup shot of a person's face in sunlight.
Shadow
An area that is shielded from direct light from a source. The shadow can be on the object that is blocking the light, such as the shadow side of a building, or it can be on another surface, such as the shadow of a building on the ground on the side opposite the sun.
Shoot
To expose film, tape, disc, etc. in a camera. To take a picture or a number of pictures. A photographic effort involving multiple photographs of a product,activity, theme, etc.
Shutter Priority
A mode of automatic exposure in which the photographer selects the shutter speed and the camera sets the aperture that will produce the correct exposure.
Soft Proof
Previewing a digital image on a computer monitor to see how it will look when printed with a particular printer, ink, and paper.
Spot Metering
A reflected light exposure meter that has a narrow angle of acceptance, typically between 1 and 8 degrees, as distinct from meters having wider angle lens acceptance such as averaging meters and center weighted meters. Spot meters allow photographers to measure the luminance in a small subject area from a distance, a feature that is especially useful when using the zone system. A circle in the viewfinder indicated the area being measured.
Stiching
Digitally combining several overlapping images of the same scene, usually seamlessly, to form a single larger image.
Strobe
An electronic flash unit that is capable of producing a rapid and continuous series of flashes of lights, used in photography, for example, to obtain a series of displaced images in a single photograph of a rapidly moving object, or of a stationary object by panning the camera. The frequency of firing is generally adjustable and on some units can be increased well beyond where it appears to be a continuous light. 2. a widely used misnomer for conventional electronic flash. 3. A shortened form of stroboscope and stroboscopic.
Subtractive color
A way to produce colors by mixing dyes or pigments that contain varying proportions of the three subtractive primary colors-cyan, magenta, and yellow.
Tenting
A way to light a highly reflective object. The object is surrounded with large sheets of paper or translucent material lighted so that the object reflects them and not the lamps, camera, and other items in the studio.
TIFF
In electronic imaging, images that are captured and saved to a storage medium as a file and are described according to some algorithm. The description is usually written prior to the image data in an area of the file called the header. Tagged image file format is one such header description widely used by electronic imaging programs. Others are TGA, VST, PCX, PICT, and PIC to name only a few. The proliferation of a multitude of image headers has caused serious porting problems. Many image manipulation software programs only read a limited number of header files. There are a number of commercial conversion programs that allow for the translation of one file format into another.
Underexposure
To give less than normal exposure to a sensor, film, or darkroom printing paper.
Viewfinder
1. A small window on a camera through which the subject is seen and framed. 2. A film camera that has a viewfinder, but not a rangefinder (which shows when the subject is focused.)
Vignetting
To underexpose or darken the corners and edges of an image. Sometimes done intentionally but more often caused accidentally by a lens that forms an image covering the light-sensitive surface only partially.
White Balance
The setting on a digital camera that adjusts the camera for the color temperature of a particular light source, such as tungsten or daylight. With the correct setting, a white object will appear white, not tinged by the color of the light source.
Wide Angle Lens
A lens whose focal length is shorter than the diagonal measurement of the sensor or film with which it is used. The angle of the view with this lens-film combination is greater at a given distance than the angle seen by the human eye. Also called a wide-angle or wide-field lens.
Zoom Lens
A lens adjustable to a range of focal lengths.