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Photography, technique of producing permanent images on sensitized surfaces by means of the photochemical action of light or other forms of radiant energy.
In today's society, photography plays important roles as an information medium, as a tool in science and technology, and as an art form, and it is also a popular hobby. It is essential at every level of business and industry, being used in advertising, documentation, photojournalism, and many other ways. Scientific research, ranging from the study of outer space to the study of the world of subatomic particles, relies heavily on photography as a tool. In the 19th century, photography was the domain of a few professionals because it required large cameras and glass photographic plates. During the first decades of the 20th century, however, with the introduction of roll film and the box camera, it came within the reach of the public as a whole. Today the industry offers amateur and professional photographers a large variety of cameras and accessories.
Basic Technology
Light is the essential ingredient in photography. Nearly all forms of photography are based on the light-sensitive properties of silver-halide crystals, chemical compounds of silver and halogens (bromine, chlorine, or iodine). When photographic film, which consists of an emulsion (a thin layer of gelatin) and a base of transparent cellulose acetate or polyester, is exposed to light, silver-halide crystals suspended in the emulsion undergo chemical changes to form what is known as a latent image on the film. When the film is processed in a chemical agent called a developer, particles of metallic silver form in areas that were exposed to light. Intense exposure causes many particles to form, while weak exposure causes few to form. The image produced in this manner is called a negative because the tonal values of the subject photographed are reversed—that is, areas in the scene that were relatively dark appear light, and areas that were bright appear dark. The tonal values of the negative are reversed again in the photographic printing process or, when preparing color transparencies (slides), in a second development process.
Photography, then, is based on chemical and physical principles. The sensitivity of silver halides to light is the primary chemical principle. The physical principles are governed by the physics of light. The generic term light refers to the visible portion of a broad range of electromagnetic radiation, which includes radio waves, gamma rays, X rays, infrared, and ultraviolet rays. The human eye is sensitive to only a narrow band of electromagnetic wavelengths, called the visible spectrum. The spectrum comprises the full range of color tones. To the eye, the longest wavelengths register as red, the shortest as blue.
Photographic Film
Photographic films vary in the way they react to different wavelengths of visible light. Early black-and-white films were sensitive only to the shorter wavelengths of the visible spectrum—that is, to light perceived as blue. Later, colored dyes were added to film emulsions to make the silver halides responsive to light of other wavelengths. These dyes absorb light of their own color, making silver halide particles sensitive to light of that color. Orthochromatic film, incorporating yellow dyes in the emulsion and sensitive to all light but red, was the first improvement on simple blue-sensitive film.
In panchromatic film, the next major improvement, red-toned dyes were added to the emulsion, rendering the film sensitive to all visible wavelengths. Although slightly less sensitive to green tones than the orthochromatic type, panchromatic film is better able to reproduce the entire range of color tones. Thus, most films now used by amateur and professional photographers are panchromatic.
Two additional varieties of black-and-white film—process and chromogenic—have their special uses. Process film is used primarily for line reproduction of copy in the graphic arts. Such films have extremely high contrast, producing images with no tonal values between black and white. Chromogenic film produces dye images rather than silver images on the negative. Using dye couplers and silver halide in the emulsion, it can be developed by standard color-negative development processes. After development, the silver is bleached out of the film, leaving a black-and-white dye image.
Special-purpose films are sensitive to wavelengths beyond the visible spectrum. In addition to visible light, infrared film also responds to the invisible, infrared portion of the spectrum.
Instant film, introduced by the Polaroid Corporation in the late 1940s, provides photographs within seconds or minutes of the taking of the picture, using a camera specially designed for this purpose. In instant film the processing chemicals and emulsion are combined in a self-contained envelope or on the print itself. Exposure, development, and printing all take place inside the camera. Polaroid, the leading manufacturer of this film, uses a conventional silver-halide emulsion. After the film is exposed and a negative image produced, the negative is sandwiched with photographic paper and processing chemicals, and a fogging agent transfers the negative image to the paper, producing a print. A number of instant films are manufactured in a 35-millimeter format, both in black and white and in color.
Color Film
Color films are more complex than black and white because they are designed to reproduce the full range of color tones as color, not as black, white, and gray tones. The design and composition of most color transparency films and color negative films are based on the principles of the subtractive color process, in which the three primary colors—yellow, magenta, and cyan (blue-green)—are combined with their complements to reproduce a full range of colors. Such films consist of three silver halide emulsions on a single layer. The top emulsion is sensitive only to blue. Beneath this is a yellow filter that blocks blues but transmits greens and reds to the second emulsion, which absorbs greens but not red. The bottom emulsion records reds.
When color film is exposed to light by a camera, latent black-and-white images are formed on each of the three emulsions. During processing, the chemical action of the developer creates actual images in metallic silver, just as in black-and-white processing. The developer combines with dye couplers incorporated into each of the emulsions to form cyan, magenta, and yellow images. Then the film is bleached, leaving a negative image in the primary colors. In color transparency film, unexposed silver-halide crystals not converted to metallic silver during the initial development are converted to positive images in dye and silver during a second stage of development. After the development action has been arrested, the film is bleached and the image fixed on it.
Film and Camera Formats
Different types of cameras require particular forms and sizes of film. Currently, the most widely used camera format is the 35 millimeter or small format, which produces 20, 24, or 36 images that each measure 24 by 36 millimeters on a roll of film. The film is wound on a spool inside a lighttight magazine or cartridge. Film for 35-millimeter cameras is also available in bulk, in long rolls that can be fed into individual cartridges and cut to length.
The next larger standard camera format, medium format, uses film sizes designated as either 120 or 220. Medium-format cameras produce images of various sizes, such as 6 by 6 centimeters or 2¼ by 2¼ inches, 6 by 7 centimeters, and 6 by 9 centimeters, depending on the configuration of the camera. Larger cameras, called view cameras, use sheet film. Standard sheet-film sizes correspond to standard view-camera formats: 4 by 5 inches, 5 by 7 inches, and 8 by 10 inches. Larger special-purpose view cameras, up to a 20-by-24 inch format, are in limited use.
Film Speed
Film is classified by speed as well as by format. Film speed is defined as an emulsion's degree of sensitivity to light, and it determines the amount of exposure required to photograph a subject under given lighting conditions. The manufacturer of the film assigns a standardized numerical rating in which high numbers correspond to "fast" emulsions and low numbers to "slow" ones. The standards set by the International Standards Organization (ISO) are used throughout the world, although some European manufacturers still use the German Industrial Standard, or Deutsche Industrie Norm (DIN). The ISO system evolved by combining the DIN system with the ASA (the industry standard previously used in the United States). The first number of an ISO rating, equivalent to an ASA rating, represents an arithmetic measure of film speed, whereas the second number, equivalent to a DIN rating, represents a logarithmic measure.
Low-speed films generally are rated from ISO 25/15 to ISO 100/21, but even slower films exist. Kodak's Rapid Process Copy Film, a special process film, has an ISO rating of 0.06/-12. Films in the ISO 125/22 to 200/24 range are considered medium speed, while films above ISO 200/24 are considered fast. In recent years, many major manufacturers have introduced superfast films with ISO ratings higher than 400/27. And certain films can be pushed well beyond their ratings by exposing them as though they had a higher rating and developing them for a greater length of time to compensate for the underexposure.
DX Coding is a recent innovation in film and camera technology. DX-coded cartridges of 35-millimeter film have printed on them a characteristic panel corresponding to an electronic code that tells the camera the ISO rating of the film as well as the number of frames on the roll. Many of the newer electronic cameras are equipped with DX sensors that electronically sense this information and automatically adjust exposures accordingly.
Differences in sensitivity of a film emulsion to light depend on various chemical additives. For example, hypersensitizing compounds increase film speed without affecting the film's color sensitivity. High-speed film can also be manufactured by increasing the concentration of large silver-halide crystals in the emulsion. In recent years, a generation of faster, more sensitive films has been created by altering the shape of crystals. Flatter silver-halide crystals offer greater surface area. Films incorporating such crystals, such as Kodak's T-grain Kodacolor films, have a correspondingly greater sensitivity to light.
The grain structure of faster films is generally heavier than that of slower films. Grain structure may give rise to a mottled pattern on prints that have been greatly enlarged. Photographs taken with slower-speed film appear less grainy when enlarged. Because of the small size of their silver-halide grains, slow-speed films generally have a higher resolution—that is, they can render fine details with greater sharpness—and can produce a broader range of tones than fast films. When tonal range and sharpness of detail are not as important as capturing a moving subject without blurring, fast films are used.
Exposure Range
Each type of film has a characteristic exposure range, or latitude of exposure. Latitude is basically the margin of error in exposure within which film, when developed and printed, can render the actual color and tonal values of the scene photographed.
The terms overexposure and underexposure are used to characterize deviations, purposeful or unintentional, from the optimum exposure. Film exposed to light for a longer time than optimal will often be "blocked up" with silver in highlight areas, resulting in a loss of contrast and sharpness and an increase in graininess. Underexposure, on the other hand, produces negatives characterized as thin, a condition in which there are not enough silver crystals for accurate rendering of dark and shadowed areas.
With films that have a narrow latitude, an exposure adjusted for a shady area is likely to result in overexposure of adjacent sunny areas. The greater a film's latitude, the greater its ability to provide satisfactory prints despite over- or underexposure. Films from which negatives are made, both color and black and white, generally offer enough latitude to allow the photographer a certain margin of error. Transparency films, from which color slides are made, generally have less latitude.
The Camera and Its Accessories
Modern cameras operate on the basic principle of the camera obscura. Light passing through a tiny hole, or aperture, into an otherwise lightproof box casts an image on the surface opposite the aperture. The addition of a lens sharpens the image, and film makes possible a fixed, reproducible image. The camera is the mechanism by which film can be exposed in a controlled manner. Although they differ in structural details, modern cameras consist of four basic components: body, shutter, diaphragm, and lens. Located in the body is a lightproof chamber in which film is held and exposed. Also in the body, located opposite the film and behind the lens, are the diaphragm and shutter. The lens, which is affixed to the front of the body, is actually a grouping of optical glass lenses. Housed in a metal ring or cylinder, it allows the photographer to focus an image on the film. The lens may be fixed in place or set in a movable mount. Objects located at various distances from the camera can be brought into sharp focus by adjusting the distance between the lens and the film.
The diaphragm, a circular aperture behind the lens, operates in conjunction with the shutter to admit light into the lighttight chamber. This opening may be fixed, as in many amateur cameras, or it may be adjustable. Adjustable diaphragms are composed of overlapping strips of metal or plastic that, when spread apart, form an opening of the same diameter as the lens; when meshed together, they form a small opening behind the center of the lens. The aperture openings correspond to numerical settings, called f-stops, on the camera or the lens.
The shutter, a spring-activated mechanical device, keeps light from entering the camera except during the interval of exposure. Most modern cameras have focal-plane or leaf shutters. Some older amateur cameras use a drop-blade shutter, consisting of a hinged piece that, when released, pulls across the diaphragm opening and exposes the film for about 1/30th of a second.
In the leaf shutter, at the moment of exposure, a cluster of meshed blades springs apart to uncover the full lens aperture and then springs shut. The focal-plane shutter consists of a black shade with a variable-size slit across its width. When released, the shade moves quickly across the film, exposing it progressively as the slit moves.
Most modern cameras also have some sort of viewing system or viewfinder to enable the photographer to see, through the lens of the camera, the scene being photographed. Single-lens reflex cameras all incorporate this design feature, and almost all general-use cameras have some form of focusing system as well as a film-advance mechanism.
Exposure Control
By adjusting shutter speed and diaphragm aperture, the photographer obtains just enough light to ensure a proper exposure. Shutter speed and aperture setting are directly proportional: A one-increment change in shutter speed is equal to a change of one f-stop. A "one-stop" adjustment in exposure can refer to a change in either shutter speed or aperture setting; the resulting change in the amount of light reaching the film will be the same. Thus, if the shutter speed is increased, a compensatory increase must be made in aperture size to allow the same amount of light to reach the film. Fast shutter speeds, 1/125th of a second or less, are more effective in capturing objects in motion.
In addition to regulating the intensity of the light that reaches the film, the diaphragm aperture is also used to control the depth of field. Also called the zone of focus, depth of field refers to the area in which objects recorded in the picture will be sharply focused. Decreasing the size of the aperture increases the overall depth of field; widening the aperture decreases the depth of field. When great depth of field is desired—maximum sharpness of all points in the scene, foreground to background—a small aperture and slow shutter speed are used. Since the faster shutter speeds needed to capture motion require, in compensation, larger apertures, the depth of field in such pictures is reduced. On many cameras, the lens ring contains a depth-of-field scale that shows the approximate sharp-focus zone for the different aperture settings.
Camera Designs
Cameras come in a variety of configurations and sizes. The first cameras, "pinhole" cameras, had no lens. The flow of light was controlled simply by blocking the pinhole. The first camera in general use, the box camera, consists of a wooden or plastic box with a simple lens and a drop-blade shutter at one end and a holder for roll film at the other. The box camera is equipped with a simple viewfinder that shows the extent of the picture area. Some models have, in addition, one or two diaphragm apertures and a simple focusing device.
The view camera, used primarily by professionals, is the camera closest in design to early cameras that is still in widespread use. Despite the unique capability of the view camera, however, other camera types, because of their greater versatility, are more commonly used by both amateurs and professionals. Chief among these are the single-lens reflex (SLR), twin-lens reflex (TLR), and rangefinder. Most SLR and rangefinder cameras use the 35-millimeter film format, while most TLR as well as some SLR and rangefinder cameras use medium-format film—that is, size 120 or 220.
View Cameras
View cameras are generally larger and heavier than medium- and small-format cameras and are most often used for studio, landscape, and architectural photography. These cameras use large-format films that produce either negatives or transparencies with far greater detail and sharpness than smaller format film. View cameras have a metal or wood base with a geared track on which two metal standards ride, one in front and one in back, connected by a bellows. The front standard contains the lens and shutter; the rear holds a framed ground-glass panel, in front of which the film holder is inserted. The body configuration of the view camera, unlike that of most general-purpose cameras, is adjustable. The front and rear standards can be shifted, tilted, raised, or swung, allowing the photographer excellent control of perspective and focus.
Rangefinder Cameras
Rangefinder cameras have a viewfinder through which the photographer sees and frames the subject or scene. The viewfinder does not, however, show the scene through the lens but instead closely approximates what the lens would record. This situation, in which the point of view of the lens does not match that of the viewfinder, results in what is known as parallax. At longer distances, the effects of parallax are negligible. At short distances, however, they become more pronounced, making it difficult for the photographer to frame a scene or subject with certainty.
Reflex Cameras
Reflex cameras, both the SLR and the TLR types, are equipped with mirrors that reflect in the viewfinder the scene to be photographed. The twin-lens reflex is box-shaped, with a viewfinder consisting of a horizontal ground-glass screen located at the top of the camera. Mounted vertically on the front panel of the camera are two lenses, one for taking photographs and the other for viewing. The lenses are coupled, so that focusing one automatically focuses the other. The image formed by the upper, or viewing, lens is reflected to the viewing screen by a fixed mirror mounted at a 45-degree angle. The photographer focuses the camera and adjusts the composition while looking at the screen. The image formed by the lower lens is focused on the film at the back of the camera. Like rangefinder cameras, TLRs are subject to parallax.
In the SLR type of reflex camera, a single lens is used for both viewing the scene and taking the photograph. A hinged mirror situated between the lens and the film reflects the image formed by the lens through a five-sided prism and onto a ground-glass screen on top of the camera. At the moment the shutter is opened, a spring automatically pulls the mirror out of the path between lens and film. Because of the prism, the image recorded on the film is almost exactly that which the camera lens "sees," without any parallax effects.
Most SLRs are precision instruments equipped with focal-plane shutters. Many have automatic exposure-control features and built-in light meters. Most modern SLRs have electronically triggered shutters. Apertures, too, may be electronically actuated or they may be adjusted manually. Increasingly, camera manufacturers produce SLRs with automatic focusing, an innovation originally reserved for amateur cameras. Minolta's Maxxum series, Canon's EOS series, and Nikon's advanced professional camera, the F-4, all have autofocus capability and are completely electronic. Central processing units (CPUs) control the electronic functions in these cameras. Minolta's Maxxum 7000i has software "cards" that, when inserted in a slot on the side of the camera, expand the camera's capabilities.
Autofocus cameras use electronics and a CPU to sample automatically the distance between camera and subject and to determine the optimum exposure level. Most autofocus cameras bounce either an infrared light beam or ultrasonic (sonar) waves off the subject to determine distance and set the focus. Some cameras, including Canon's EOS and Nikon's SLRs, use passive autofocus systems. Instead of emitting waves or beams, these cameras automatically adjust the focus of the lens until sensors detect the area of maximum contrast in a rectangular target at the center of the focusing screen.
Design Comparisons
Of the three most widely used designs, the SLR is the most popular among both professionals and amateurs. Its greatest advantage is that the image seen through the viewfinder is virtually identical with that on which the lens is focused. In addition, the SLR is generally easy and fast to operate and comes with a greater variety of interchangeable lenses and accessories than the other two camera types.
The rangefinder camera, previously used by photojournalists because of its compact size and ease of operation (compared with the big, slow 4-by-5 inch press cameras used by an earlier generation) has largely been replaced by the SLR. Rangefinder cameras, however, have a simpler optical system with fewer moving parts and are thus inherently more sturdy than SLRs, in addition to being quieter and weighing less. For these reasons, some photographers, mainly professionals, continue to use them.
Compared with the other two designs, TLRs have a relatively slow focusing system. As with rangefinder cameras, fewer interchangeable lenses are available, yet the TLR remains popular. The camera produces larger negatives than most SLRs and rangefinders, an advantage when fine detail must be rendered in the final image. In recognition of this, some manufacturers—including Hasselblad, Mamiya, Bronica, and Rollei—have combined the convenience of the SLR with the medium-film format, further reducing the market for the TLR.
Some cameras are designed primarily for amateurs: They are simple to operate, and they produce photographs acceptable to the average snapshot photographer. Many "point-and-shoot" amateur cameras now employ sophisticated technology, with features such as autofocus and exposure-control systems that simplify the process of taking pictures and almost guarantee good-quality photos.
Camera Lenses
The lens is as important a part of a camera as the body. Lenses are referred to in generic terms as wide-angle, normal, and telephoto. The three terms refer to the focal length of the lens, which is customarily measured in millimeters. Focal length is defined as the distance from the center of the lens to the image it forms when the source is at infinity. In practice, focal length affects the field of view, magnification, and depth of field of a lens.
Cameras used by professional photographers and serious amateurs are designed to accept all three lens types interchangeably. In 35-millimeter photography, lenses with focal lengths from 20 to 35 millimeters are considered wide-angle lenses. They provide greater depth of field and encompass a larger field (or angle) of view but provide relatively low magnification. Extreme wide-angle, or fish-eye, lenses provide fields of view of 180 degrees or more. A 6-millimeter fish-eye lens made by Nikon has a 220-degree field of view that produces a circular image on film, rather than the normal rectangular or square image.
Lenses with focal lengths from 45 to 55 millimeters are referred to as normal lenses because they produce an image that approximates the field of view of the human eye. Lenses with longer focal lengths, called telephoto lenses, constrict the field of view and decrease the depth of field while greatly magnifying the image. For a 35-millimeter camera, lenses with focal lengths of 85 millimeters or more are considered telephoto.
A fourth generic lens type, the zoom lens, is designed to have a variable focal length, which can be adjusted continuously between two fixed limits. Zoom lenses are especially useful in conjunction with single-lens reflex cameras, for which they allow continuous control of image scale.
Artificial Light Sources
In the absence of adequate sunlight, photographers use artificial light to illuminate scenes, both indoors and outdoors. The most commonly used sources of artificial illumination are the electronic flash, or "strobe"; tungsten lamps called photofloods; and quartz lamps. Another once-popular light source, the flashbulb, a disposable bulb filled with oxygen and a mass of fine magnesium alloy wire that fired only once, is largely obsolete, having been replaced by inexpensive, economical electronic flash units.
The electronic flash consists of a glass quartz tube filled with an inert gas—a halogen—at extremely low pressure. When high voltage is applied to the electrodes sealed at the ends of the tube, the gas ionizes and produces an intense burst of light of very short duration—a flash. Although large, special-purpose units can produce a flash of about 1/100,000 of a second, most produce flashes lasting from 1/5000 to 1/1000 of a second. Flash units must be synchronized with the shutter of the camera so that the burst of light covers the entire scene. Synchronization is achieved through an electrical connection between camera and flash unit—either a bracket mounted on top of the camera, called a hot shoe, or a cord called a synch cord that runs from the camera's synchronization socket to the flash.
Automatic flash units are equipped with sensors, photocells that automatically adjust the duration of the flash for a particular scene. The sensor, which measures the intensity of the flash as it occurs, cuts off the light when adequate illumination is obtained. The dedicated flash, a newer type of automatic flash, is designed to function as a unit with a particular camera. The electronic circuitry of the flash and camera are integrated. The sensor is located inside the camera and gauges the amount of light at the film plane, allowing more accurate measurement of flash intensity.
Flash units vary in size from small camera-mounted units to large studio units. Generally speaking, the larger the unit, the greater the intensity of light produced. Camera-mounted flashes are adequate for illuminating small scenes, but to illuminate a large scene evenly, and with a single burst of light, a powerful studio unit is needed.
Photofloods, incandescent bulbs with filaments thinner than those used in ordinary light bulbs, provide continuous light. For normal color rendition in color photography, photofloods must be used with either tungsten-balanced film or a light-balancing filter. Quartz lighting, the standard of the television industry because of the great intensity of light produced and relative longevity of the bulbs when compared to tungsten sources, is also popular among still photographers.
Exposure Meters
Serious photographers use exposure meters to measure the intensity of light in a given situation to determine the proper combination of shutter speed and diaphragm aperture. The major types of meters are incident-light and reflected-light meters.
Incident-light meters measure the intensity of light falling on a subject. To take an incident-light reading, the meter is placed alongside the subject and pointed at the camera. Reflected-light meters measure the intensity of light reflected by the subject. They are read with the meter at the camera, pointed toward the subject. Most incident-light meters can also be modified for use as reflected-light meters.
A type of meter called a spot meter measures reflected light in an area as little as 1 degree, whereas the types mentioned above cover a much broader angular range: from 30 degrees to 50 degrees for a reflected-light meter, and to 180 degrees for an incident-light meter. Flash meters are designed to measure only the split-second bursts emitted by flash units. Combination meters are designed with incident-light, reflected-light, and flash-metering capability.
The simplest meters contain a photoelectric cell that generates a tiny electric current when exposed to light and moves a pointer across a scale. The meter is equipped with an adjustable dial indicating film speed. When the dial is aligned with the pointer, the meter shows the various combinations of shutter speeds and apertures that will produce equivalent exposures, and the camera can be set accordingly.
In some meters, a photoconductive cadmium sulfide cell serves as the light-sensitive element. Powered by a mercury battery, the cell is extremely sensitive, even under low-light conditions. A late-1980s innovation was the use of silicon diodes as the light receptor. Meters equipped with these have even greater sensitivity to light than cadmium sulfide cells.
For studio photography, a special meter that measures the color temperature of light is often used. Different wavelengths of light correspond to particular temperatures, expressed in degrees Kelvin (K), and different kinds of lighting have their own specific color temperatures. Color-temperature meters allow precise measurement of the light emitted by various kinds of bulbs. This is essential for professional color photography done indoors under artificial lighting because the color temperature of fluorescent and incandescent bulbs varies from manufacturer to manufacturer, and the color temperature of a bulb can also change with age.
Filters
Made of gelatin or glass, filters are used in front of a camera lens to alter the color balance of light, to change contrast or brightness, to minimize haze, or to create special effects. In black-and-white photography, color filters are used with panchromatic film to transmit light of the matching color while blocking light of a contrasting color. In a landscape photograph taken with a red filter, for example, some of the blue light of the sky is blocked, causing the sky to appear darker and thereby emphasizing clouds. Under a blue sky, a yellow filter produces a less extreme effect because more blue light is transmitted to the film. The No. 8 yellow filter is often used for outdoor black-and-white photography because it renders the tone of a blue sky in much the same way that the human eye perceives it.
Conversion filters, light-balancing filters, and color-compensating filters are all widely used in color photography. Conversion filters change the color balance of light for a given film. Tungsten films, for example, are designed and balanced for the color temperature of amber tungsten light. Exposed in daylight, they will produce pictures with a bluish cast. A series 85 conversion filter can correct this. Daylight film, on the other hand, balanced for sunlight at noon, which has a greater concentration of blue wavelengths than tungsten light, will have a yellow-amber cast when exposed under tungsten light. A series 80 conversion filter corrects this problem.
Light-balancing filters are generally used to make small adjustments in color. These pale-toned filters eliminate undesirable color casts or add a general warming hue. Color-compensating (CC) magenta filters can balance greenish fluorescent light for daylight or tungsten film. Another type of filter, the polarizer, is used primarily to reduce reflection from the surface of shiny subjects. Polarizing filters are also used in color photography to increase color saturation.
Developing and Printing
The latent image on film becomes visible through the process called developing—the application of certain chemical solutions to transform the film into a negative. The process in which this negative is used to create a positive image is called printing, and the image is called a print. Film is developed by treating it with a weak reducing alkaline chemical called the developing solution, or developer. This solution reactivates the process begun by the action of light when the film was exposed. The effect is to reduce further the silver-halide crystals in which metallic silver had already formed, so that large grains of silver form around the minute particles that make up the latent image.
As large particles of silver begin forming, a visible image becomes apparent on the film. The thickness and density of silver deposited in each area depend on the amount of light received by the area during exposure. In order to arrest the action of the developer, the film is then bathed in a weakly acidic solution, which neutralizes the alkaline developer. After rinsing, the negative image is fixed: Residual silver-halide crystals are removed, and remaining metallic silver particles are stabilized. The chemical solution used for fixing, commonly referred to as hypo, or fixer, is usually sodium thiosulfate, although potassium or ammonium thiosulfate may also be used. Fixer remover, or hypo clearing agent, is then used to rinse any remaining fixer from the film. Film must be rinsed thoroughly in water, as residual fixer tends to destroy negatives with time. Finally, bathing the processed film in a washing aid promotes uniform drying and prevents formation of water spots and streaks.
Printing is done by either of two methods: contact or projection. The contact method is used when prints of exactly the same size as the negative are desired. They are made by placing the emulsion side of the negative in contact with the printing material and exposing the two together under a source of light.
In projection printing, the negative is first placed in a type of projector called an enlarger. Light from the enlarger passes through the negative to a lens, which projects an enlarged or reduced image of the negative onto sensitized printing material. The process allows the photographer to reduce or increase the amount of light falling on particular portions of the printing material. Known as dodging and burning, these techniques render the final print lighter or darker in selected areas.
The printing material used in this process is a type of photographic paper similar in composition to that used for film, but much less sensitive to light. After it has been exposed, the print is developed and fixed by a process very similar to that used for developing film. In the finished print, areas exposed to the most light reproduce as dark tones, areas that were blocked from light by the negative reproduce as light tones, and areas exposed to moderate amounts of light reproduce as intermediate tones.
Color prints from color negatives are made either by the projection method or by contact printing. Prints from color transparencies can be made directly by projection using the Cibachrome process or a Type R process, such as Kodak's R-3 or Fuji's Type 34. Alternatively, color transparencies can be printed by first making an intermediate negative, or internegative, which can then be printed either by contact or by projection. A third color-printing process, called dye-transfer, is considerably more complex and is generally used only for professional work.
Positive color transparencies and color negatives are printed on papers with multilayer emulsions containing color-forming agents. Examples of these are Fujichrome Type 34 process paper and Kodak Ektachrome, which are used for printing from color transparencies; and Ektacolor, Fujicolor, and Agfacolor CN Type A, which are used for printing from negatives. These papers are developed in dye-forming solutions without reversal processing. When color prints of this type are made, errors in exposure can be minimized by varying print exposure time. Color balance is controlled by adjustable filters in the head of the enlarger, between the light source and the negative.
In the dye-transfer process of making color prints, a separate negative is prepared for each of three colors: red, green, and blue. These color-separation negatives are either produced directly from the subject in a one-shot camera, now a relatively obsolete technique, or are produced indirectly from the color transparency. The negatives are then used to produce positive-relief images on gelatin sheets known as matrices. Three positive matrices are produced; one is steeped in red dye, another in blue, and the third in green. After immersion, each matrix is printed in turn on a special easel that ensures precise alignment, or registration, to form a full-color image.
Recent Technological Advances
New technologies are beginning to blur the lines between photography and other image-making systems. In some new forms of still photography, silver-halide emulsions have been replaced by electronic methods of recording visual information. The Sony Corporation has developed a still-video camera called the Mavica, based on an earlier industrial model, the ProMavica. Unlike the conventional video camera, which uses magnetic tape, the Mavica records visual data—light reflected from objects in the scene photographed—on a floppy disk. The images are viewed on a monitor connected to the Mavica's playback unit. Canon U.S.A. has also entered the still-video-camera market. Its RC-470 camera requires a still-video player for viewing, but the Xap Shot, which records 50 still images, with 300 to 400 lines of resolution, on a 5-cm (2-in) floppy disk, does not require any special equipment. It can be connected directly to a television receiver. Paper prints of the recorded images can also be made, using a special, laser-driver computer printer.
Digitization of photographic images has begun to revolutionize professional photography, giving rise to a specialized field known as image processing. Digitization of the visual data in a photograph—that is, conversion of the data into binary numbers using a computer—makes it possible to manipulate the photographic image by means of specially developed computer programs. The Scitex image-processing system, the commercial and advertising industry standard in the late 1980s, enables the operator to move or erase elements in a photograph, to change colors, to fashion composite images from several photographs, and to adjust contrast or sharpness. Other less sophisticated systems, such as Macintosh's Digital Darkroom, allow similar operations.
The quality of computer-generated images was, until recently, inferior to strictly photographic images. Most nonindustrial color printers and laser printers cannot yet produce images with the tonal range, resolution, and saturation of photographs. Some systems, however, such as Presentation Technologies' Montage Slidewriter and the Linotronic system, are capable of producing magazine-quality images.
Special Techniques
By the end of the 19th century, photography was already playing an important specialized role in astronomy. Since that time, many special photographic techniques have been developed. They serve as important tools in a number of scientific and technological areas.
High-Speed Photography and Cinematography
Extremely fast motion can also be studied by high-speed cinematography. Conventional techniques, in which individual still photographs are taken in a fast sequence, allow a maximum rate of 500 frames per second. By keeping the film stationary and using a fast rotating mirror (up to 5000 revolutions per second) that moves the images in a sequential order over the film, rates of a million pictures per second can be attained. For extremely high rates, such as a billion pictures per second, classical optical
Most modern cameras allow exposures with shutter speeds of up to 1/1000 second. Shorter exposure times can be attained by illuminating the object with a short light flash. In 1931 American engineer Harold E. Edgerton developed an electronic strobe light with which he produced flashes of 1/500,000 second, enabling him to photograph a bullet in flight. By the use of a series of flashes, the progressive stages of objects in motion, such as a flying bird, can be recorded on the same piece of film. Synchronization of the flash and the moving object is achieved by using a photocell to trigger the strobe light. The photocell is set up so that it is illuminated by a beam of light that is interrupted by the fast-moving object as soon as the object comes into the field of the camera.
More recently, high-speed electro-optical and magneto-optical shutters have been developed that allow exposure times of up to a few billionths of a second. Both types of shutters make use of the fact that the polarization plane of polarized light in certain materials is rotated under the influence of an electric or magnetic field. The magneto-optical shutter is made up of a glass cylinder that is placed inside a coil. A polarization filter is placed at each side of the glass cylinder. Both filters are crossed, and light that passes through the first filter becomes polarized and is stopped by the second filter. If a short electric pulse is passed through the coil, the polarization plane of the light in the glass cylinder is rotated, and light can pass through the system.
The electro-optical shutter, built in a similar way, consists of a cell with two electrodes that is filled with nitrobenzene and is placed between the two crossed polarization filters. The polarization plane inside the liquid is rotated by a short electrical pulse at the electrodes. Electro-optical shutters have been used to photograph the sequence of events during an explosion of an atomic bomb.
methods are abandoned and cathode ray tubes are used to make the exposures.
Aerial Photography
Special cameras are often equipped with several lenses and large film magazines and mounted vibration-free on airplanes. They are used in extensive land surveys for mapmaking, for studying the growth of cities for city planning, for detecting traces left by ancient civilizations, and for observing land use and the distribution of animal populations and vegetation. Cameras mounted in satellites are also used for such photography. A special application of aerial photography is military surveillance and reconnaissance. Some reconnaissance satellites are equipped with cameras with long focal lengths that produce images of extremely high resolution, on which cars and trucks can be recognized. Advanced satellite photographic methods, which until recently were used almost exclusively by military, intelligence, and weather agencies, are increasingly being employed by geologists to uncover mineral resources and by news organizations to obtain instantaneous photographs of distant news events.
Underwater Photography
Underwater cameras require a watertight housing with a glass or plastic window in front of the lens. Usually, during daytime, photographs can be taken at depths to 10 m (more than 30 ft). Greater depths require artificial light, such as an electronic flash or floodlight. The quality of the photographs depends on the clarity of the water. In water full of particles, the light reflected from the particles renders anything but close-ups impractical. Underwater photographers often use wide-angle lenses to compensate for the fact that anything under water appears 25 percent closer than it is in reality, because the refractive index of water is greater than that of air. Recording the beauty of the underwater world with the camera is a popular activity of scuba-diving enthusiasts. Special underwater cameras in pressure-resistant housings are also used in deep-sea exploration.
Scientific Photography
In scientific research, photographic plates and films are among the most important recording tools, not only because of their versatility but also because the photographic emulsion is sensitive to ultraviolet and infrared light, to X rays and gamma rays, and to charged particles. Radioactivity, for example, was discovered because of the accidental blackening of photographic film. Many optical instruments, such as the microscope, the telescope, and the spectroscope, can be used to obtain photographs. Many other scientific instruments, such as electron microscopes, oscilloscopes, and computer terminals, are also equipped with devices to take photographs or with adapters that permit the use of a regular camera. In laboratory research, Polaroid cameras are often used to obtain quick results. An important research activity in particle physics is the study of thousands of photographs taken in cloud or bubble chambers in order to find interactions between particles of interest. Tracks of charged particles can also be recorded directly on special films.
The photographic recording of X-ray pictures, called radiography, has become an important diagnostic tool in medicine. Radiography, using very energetic X rays or gamma rays, is also employed to detect welding defects and structural defects in pressure vessels, pipes, and mechanical parts, especially those that are critical for safety reasons, as in nuclear power plants, airplanes, and submarines. In many cases the film, wrapped in a lighttight envelope, is simply applied against one side of the object, while the object is irradiated from the other side. The photographic recording of X rays is also used in structural studies of crystalline materials. With the development of the laser, a technique called lensless photography, or holography, became available for producing three-dimensional images.
Astronomical Photography
In no other field of science has photography played a more important role than in astronomy. By placing the photographic plate in the focal plane of a telescope, astronomers can obtain precise records of the locations and brightness of celestial bodies. By comparing photographs of the same region of the sky taken at different times, proper motions of certain objects such as comets can be detected. An important quality of the photographic plate for astronomy is its ability to record, by means of long time exposures, faint astronomical objects that cannot be observed visually.
Recently, the sensitivity of photographic recording has been improved by image-enhancing techniques. Starlight liberates electrons on a photocathode that is placed in the focal plane of the telescope. The liberated electrons are directed to a photographic plate to form the image. Computer enhancement techniques create sharper, more detailed images from sometimes fuzzy and distant photographs from outer space. The computers digitize the photographic information and then reproduce it with greatly improved resolution.
Microfilming
Microfilming consists of photographically reducing images to a very small size. An early application was the photographing of bank checks in the 1920s. Now the technique is widely used to store information that otherwise would require too much space. For example, newspapers and magazines are photographed on roll film and can be displayed on desktop projectors equipped with systems that permit the desired pages to be found quickly. Another application is the microfiche, a piece of 10-by-15-cm (4-by-6-in) film on which up to 70 frames, each corresponding to one page of text, can be stored. Each frame can be viewed individually on a desktop projector. This system makes possible the storage of the entire catalog of a library on a relatively small number of microfiches.
Infrared Photography
With special dyes, photographic emulsions can be made sensitive to light in the invisible infrared portion of the spectrum. Infrared light cuts through haze and enables clear photographs to be taken from long distances or high altitudes. Because any object radiates in infrared light, it can be photographed in complete darkness. Infrared photographic techniques are used wherever small differences in temperature, or in absorption or reflection capacities for infrared light, have to be detected. Some substances, particularly organic ones such as vegetation, reflect infrared light more strongly than other substances do. Infrared films tend to reproduce as white the tones of green leaves and plants, especially if used in conjunction with a deep-red filter. Infrared film has many technical and military applications, including the detection of camouflage, which in the infrared photograph appears darker than the surrounding area. Infrared photography is also used in medical diagnosis, in the detection of forgeries in handwriting as well as in paintings, and for the study of deteriorated documents. It was used, for example, in deciphering the Dead Sea Scrolls.
Ultraviolet Photography
Normal film is sensitive to ultraviolet light. In one method of ultraviolet photography, an ultraviolet light source is used to illuminate the object, and the camera lens is provided with a filter that permits only the passage of ultraviolet light. The second method makes use of fluorescence caused by ultraviolet light: A filter used on the camera absorbs ultraviolet light and allows the passage of the fluorescent light. One important application of ultraviolet photography is the study of forged documents, because traces of erased writing become detectable in ultraviolet light.
In several processes used to produce photographic images in the ultraviolet range of the spectrum, plastics and other chemicals that react to ultraviolet light replace the silver-halide emulsion of conventional film. In one process, surface areas of a plastic substance exposed to ultraviolet rays harden in direct proportion to the amount of exposure, and removal of the unhardened areas leaves a raised photographic image. In other processes, a thin film of chemicals is suspended between plastic sheets. When exposed to ultraviolet rays, these chemicals emit gas bubbles, in amounts proportional to the exposure received in the area. The bubbles expand and become visible when heat is applied to the sheets, creating a transparency in which the gas bubbles form the image. Another type of plastic, when heated, reacts chemically with the gas bubbles so that a stained positive image is obtained on the plastic sheets.
In the photochromic film developed by the National Cash Register Company, a dye sensitive to ultraviolet light is used. Because the dye has no grain structure, enormous enlargements can be made. For example, enlargements can be made from film on which a complete book is contained in an area the size of a postage stamp.
Historical Development
The term camera, as well as the apparatus itself, derives from camera obscura, which is Latin for "dark room" or "dark chamber." The original camera obscura was a darkened room with a minute hole in one wall. Light entering the room through this hole projected an image from the outside on the opposite, darkened wall. Although the image formed this way was inverted and blurry, artists used this device, long before film was invented, to sketch by hand scenes projected by the "camera." Over the course of three centuries, the camera obscura evolved into a handheld box, and the pinhole was fitted with an optical lens to sharpen the image.
18th Century
The photosensitivity of certain silver compounds, particularly silver nitrate and silver chloride, had been known for some time before British scientists Thomas Wedgwood and Sir Humphry Davy began experiments late in the 18th century in the recording of photographic images. Using paper coated with silver chloride, they succeeded in producing images of paintings, silhouettes of leaves, and human profiles. These photographs were not permanent, however, because the entire surface of the paper blackened after exposure to light.
19th Century
The earliest photographs on record, known as heliographs, were made in 1827 by French physicist Joseph Nicéphore Niépce. About 1831 French painter Louis Jacques Mandé Daguerre made photographs on silver plates coated with a light-sensitive layer of silver iodide. After exposing the plate for several minutes, Daguerre used mercury vapors to develop a positive photographic image. These photographs were not permanent because the plates gradually darkened, obliterating the image. In the first permanent photographs made by Daguerre, the developed plate was coated with a strong solution of ordinary table salt. This fixing process, originated by British inventor William Henry Fox Talbot, rendered the unexposed silver-iodide particles insensitive to light and prevented total blackening of the plate. The Daguerre method produced an unreproducible image on the silver plate for each exposure made.
While Daguerre perfected his process, Talbot developed a photographic method involving the use of a paper negative from which an unlimited number of prints could be made. Talbot had discovered that paper coated with silver iodide could be made more sensitive to light if dampened before exposure by a solution of silver nitrate and gallic acid, and that the solution also could be used in developing the paper after exposure. After development, the negative image was made permanent by immersion in sodium thiosulfate, or hypo. Talbot's method, called the calotype process, required exposures of about 30 seconds to produce an adequate image on the negative. Both Daguerre and Talbot announced their processes in 1839. Within three years the exposure time in both processes had been reduced to several seconds.
In the calotype process, the grain structure of the paper negatives appeared in the finished print. In 1847 French physicist Claude Félix Abel Niépce de Saint-Victor devised a method of using a glass-plate negative. The plate, which was coated with potassium bromide suspended in albumin, was prepared before exposure by immersion in a silver-nitrate solution. The glass-plate negatives provided excellent image definition but required long exposures.
In 1851 British sculptor and photographer Frederick Scott Archer introduced wet glass plates using collodion, rather than albumin, as the coating material in which light-sensitive compounds were suspended. Because these negatives had to be exposed and developed while wet, photographers needed a darkroom close at hand in order to prepare the plates before exposure and to develop them immediately after exposure. Using wet collodion negatives and horse-drawn mobile darkrooms, photographers on the staff of American photographer Mathew B. Brady took thousands of photographs on battlefield sites during the American Civil War (1861-1865).
Because use of the wet collodion process was limited largely to professional photography, various experimenters attempted to perfect a type of negative that could be exposed when dry and that would not require immediate development after exposure. Advances were made by British merchant Richard Kennett, who supplied dry-plate negatives to photographers as early as 1874. In 1878 British photographer Charles Bennett produced a dry plate coated with an emulsion of gelatin and silver bromide, which was similar to modern plates.
While experiments were being performed to increase the efficiency of black-and-white photography, preliminary efforts were made to use the coated-plate emulsions to produce natural color images of photographic subjects. In 1861 the first successful color photograph was made by British physicist James Clerk Maxwell, who used an additive-color process.
About 1883, American inventor George Eastman produced a film consisting of a long paper strip coated with a sensitive emulsion. In 1889 Eastman produced the first transparent, flexible film support, in the form of ribbons of cellulose nitrate. The invention of roll film marked the end of the early photographic era and the beginning of a period during which thousands of amateur photographers became interested in the new process.
20th Century
In the early 20th century, commercial photography grew rapidly, and improvements in black-and-white photography opened the field to individuals lacking the time and skill to master the earlier, more complicated processes. The first commercial color-film materials, coated glass plates called Autochromes Lumière—after the process developed by French inventors Auguste and Louis Lumière—became available in 1907. During this period, color photographs were produced with the three-exposure camera.
In the 1920s improvement of photomechanical processes used in printing created a great demand for photographs to illustrate text in newspapers and magazines. The demand for photographic illustrations with printed material established the new commercial fields of advertising and publicity photography. Technological advances, which simplified photographic materials and apparatus, encouraged the widespread adoption of photography as a hobby or avocation by great numbers of people.
The 35-millimeter camera, which used small-sized film designed initially for motion pictures, was introduced in 1925 in Germany, and because of its compactness and economy, it became popular with both amateur and professional photographers. During this period, finely powdered magnesium was used by professional photographers as an artificial illuminant. Sprinkled in a trough and fired with a percussion cap, it produced a brilliant flash of light and a cloud of acrid smoke. In the 1930s the photographic flashbulb replaced magnesium powder as a light source.
The advent in 1935 of Kodachrome color film and in 1936 of Agfacolor, both of which produced positive color transparencies, or slides, initiated the popular use of color film. Kodacolor negative color film, introduced in 1941, gave further impetus to its widespread use.
Many photographic processes that were developed for the military during World War II (1939-1945) were released for general use at the end of the war. These advances included new chemicals for film development and fixing. The perfection of electronic computers greatly facilitated the solution of mathematical problems involved in lens design, and many new lenses became available, including interchangeable lenses for existing camera types. In 1947 the Polaroid Land camera, based on a photographic process devised by American physicist Edwin H. Land, added to amateur photography the appeal of prints that could be developed and finished in the camera immediately after exposure.
During the 1950s, new manufacturing processes greatly increased the speed, or light sensitivity, of both black-and-white and color films. Black-and-white film speeds rose from a maximum of about ISO 100 to a theoretical maximum of about ISO 5000, and color film speeds increased tenfold. This decade was also marked by the introduction of electronic devices called light amplifiers, which intensify dim illumination, making possible the recording on photographic film of even the faint light of very distant stars. Such advances in mechanical devices systematically raised the technical level of both amateur and professional photography.
A film called Itek RS that uses relatively inexpensive chemicals such as zinc, cadmium sulfide, and titanium oxide instead of the more expensive silver compounds was also introduced in the 1960s. A new technique called photopolymerization made possible the production of contact prints on ordinary, unsensitized paper. For other recent developments, see Special Techniques, above.
The Art of Photography
Photographs are taken for any number of reasons, which can be grouped into three main approaches: photography as reportage, to record the external world as it appears; photography as art, used for expressive, interpretive purposes; and commercial photography.
Reportage includes documentary photography and photojournalism and is generally nonmanipulative in technique. The photographic reporter usually employs only those camera techniques and developing processes necessary to produce an image under existing conditions. While it is possible to describe this approach as objective, the eye behind any camera inevitably makes a selection of what is to be recorded. This selection may be planned ahead of time or calculated on the spot. The intention and ultimate use of photo reportage must also be taken into account: The most factual and presumably dispassionate of photographic images may be used for propaganda or advertising purposes.
Art photography, on the other hand, is entirely subjective, although it may use either a nonmanipulative or a manipulative approach. In the latter case, lighting, focus, and camera angle may be manipulated to alter the appearance of the image; the developing and printing processes may be modified to produce desired results; or the photograph may be combined with other media to produce a composite art form.
Photo Reportage
In a sense, of course, all photography is reportage, recording an image of what the eye and camera lens behold. The earliest experimenters with the medium looked on it as no more than a form of reportage. By the 1860s, however, a split in theory divided those photographers who continued to use the camera to record straightforwardly from those who claimed photography to be an alternative for the other visual arts. Documentary photography combines the use of pictures as record and as evidence. A subgenre may be distinguished as social documentary.
Documentary Photography
Among the earliest documentary photographs are those taken by English photographer Roger Fenton, which brought vivid images of the Crimean War (1853-1856) to English viewers. The grim realities of the American Civil War were documented by Mathew B. Brady, Alexander Gardner, and Timothy H. O'Sullivan. After the war, Gardner and O'Sullivan extensively photographed the western region of the United States, along with Carleton E. Watkins; Eadweard Muybridge, better known for his studies of figures in motion; William Henry Jackson, whose images of the Yellowstone area were instrumental in making it the first national park; and Edward Sheriff Curtis, who did a series of studies of Native Americans. The clear, detailed prints of these photographers provide a permanent record of the unspoiled wilderness.
Views of other scenic places and of exotic lands are preserved in the work of a number of 19th-century English photographers who traveled incredible distances laden with the cumbersome equipment of the day to record scenes and people. Francis Bedford photographed the Middle East in 1860; his compatriot Samuel Bourne made about 900 pictures of the Himalayas on three trips between 1863 and 1866; and Francis Frith worked in Egypt about 1860. His photographs of sites and monuments (many of which are now destroyed or dispersed) provide a record still useful to archaeologists, as do those pictures taken from 1849 to 1851 by French photographer Maxime DuCamp.
A popular form of home entertainment in the 19th century was provided by the stereoscope pictures taken by these traveling photographers, using double-lens cameras. When viewed through a special holder, these photographs take on a three-dimensional quality.
With Charles Bennett's invention of the dry plate negative in 1878, the task of the traveling view photographer became much less arduous. Instead of having to develop the plate on the spot, while it was still wet, a photographer could store the dry plate to be developed elsewhere at a later time.
Interest in such view photographs has been revived in recent years, and they have been the subject of several exhibitions and books. These include Imperial China: Photographs 1850-1912 (based on a 1979 exhibition at Asia House Gallery, New York City); Princely India: Photographs of Raja Deer Lala Dayal, Court Photographer (1884-1910) to the Premier Prince of India (1980), edited by Clark Worswick; and Photographs for the Tsar: The Pioneering Color Photography of Sergei Mikhailovich Prokudin-Gorskii Commissioned by Tsar Nicholas II (1980). This last publication is a collection of photographs of czarist Russia between 1909 and 1914, purchased in 1948 by the Library of Congress.
Social Documentary
Instead of recording life in other parts of the world, a number of 19th-century photographers devoted themselves, with more subjective concern, to documenting life and conditions immediately about them. Thus, English photographer John Thomson documented the ordinary life of London's working class during the 1870s in his volume of photographs, with accompanying text, Street Life in London (1877), and Danish-born American police reporter Jacob August Riis did a series of photographs of the slums of New York City from 1887 to 1892. With the intent of forcing a change in slum conditions, Riis brought them to the attention of the public in two photographic volumes: How the Other Half Lives (1890) and Children of the Poor (1892). These pictures—and Riis's written commentary—were directly responsible for positive social changes. Between 1905 and 1910, Lewis Wickes Hine, an American sociologist and champion of child labor laws, also recorded the oppressed members of American society in his pictures of ironworkers and steelworkers, miners, impoverished European immigrants, and especially child laborers. Although his photographs were not consciously taken for documentary purposes, an invaluable record of the life of an American black community is preserved in the work of American James Van Der Zee, who photographed residents of Harlem, in New York City, for many decades.
The city photographs of French photographer Eugène Atget stand halfway between social documentary and art photography. Their superb composition and expression of personal vision transcend a purely documentary function. Atget, perhaps one of the most prolific of the documentarians at the turn of the century, made an enormous number of often poetic scenes of ordinary life in and around his beloved Paris between 1898 and 1927. The preservation and publication of his work is due to the efforts of another gifted documenter of the urban scene, American Berenice Abbott, many of whose photographs record New York City of the 1930s.
During the Great Depression of the 1930s, a group of photographers was hired by the United States Farm Security Administration to document those areas of the country hardest hit by the catastrophe. The photographers, including Walker Evans, Russell Lee, Dorothea Lange, Ben Shahn, and Arthur Rothstein, documented the condition of the poverty-stricken rural United States. The result—pictures of migratory workers and sharecroppers and their homes, schools, churches, and belongings—was extremely persuasive both as evidence and as art. Evans's contributions, with a text by American writer James Agee, were separately published under the title Let Us Now Praise Famous Men (1941); the book is considered a classic in its field.
Photojournalism
Photojournalism differs from other documentary photography in that its purpose is to tell a particular story in visual terms. Photojournalists work for daily and periodical newspapers, magazines, news wire services, and other news publications covering events in areas ranging from sports to the arts to politics. One of the foremost photojournalists was Frenchman Henri Cartier-Bresson, who from 1930 worked to document what he calls the "decisive moment." He believed that the dynamics in any given situation eventually reach a peak, at which time a photograph will capture the most powerful image possible. Sensing ahead of time that exact peak moment to trip the shutter is a technique of which Cartier-Bresson became a master. Technological advances in the 1930s in equipment (notably improvements in small cameras such as the Leica) and in film sensitivity facilitated such recording of instantaneous vision. Many of Cartier-Bresson's images are as strong in design as they are in emotion and are considered to be fine art, photojournalism, and documents simultaneously.
Another French photojournalist, Hungarian-born Brassaï, was also committed to recording the fleeting expressive moment—in his case, the more provocative side of Parisian nightlife. His photographs were collected and published as Paris de nuit (1933).
American war correspondent Robert Capa began his career photographing the Spanish Civil War (1936-1939). Like Cartier-Bresson, he was interested in recording the impact on civilians as well as battle scenes. Capa also covered the 1944 landing of U.S. troops in Europe on D-Day in World War II, and the war between the French and the Indochinese, during which, in 1954, he was killed. The works of English photographer Donald McCullin provide a powerful indictment of war. His images of battle and its effects are collected in The Destruction Business (1971) and Is Anyone Taking Any Notice? (1973).
In the late 1930s such pictorial magazines as Life and Look in the United States and Picture Post in England were established. These publications featured photographic essays with text based on and subordinate to the pictures. This widely popular form is particularly associated with Life's famous staff photographers Margaret Bourke-White and W. Eugene Smith. An example of Bourke-White's work now recognized as an important American historical document is an 11-page spread devoted to life in Muncie, Indiana. These magazines went on to provide extensive photographic coverage of World War II and the Korean War (1950-1953), with pictures taken by Bourke-White, Capa, Smith, David Douglas Duncan, and several other American photojournalists. Subsequently, using photographs to bring about social change—like Riis before him—Smith documented the horrible effects of mercury poisoning in Minamata, a Japanese fishing village contaminated by leakage from a local industrial plant. Two documentary photographers who have produced extraordinarily expressive works are Ernest Cole, whose House of Bondage (1967) explores the miseries of the apartheid system, and Czech Josef Koudelka, noted for his splendidly composed narrative pictures of Eastern Europe's Roma (Gypsies).
Commercial and Publicity Photography
Just as photography has been used to inspire and influence social or political opinion, it has also been used, since the 1920s, to encourage and direct consumerism and as an adjunct to publicity efforts. Commercial photographers produce photographs that are used in advertisements or as illustrations in books, magazines, and other publications. They use a range of sophisticated techniques to make their photographs attractive and compelling. The impact of this type of imagery has proved to be a strong cultural influence. Commercial and publicity photography also has been a driving force behind the evolution of high-quality photographic reproduction on the printed page. Notable in this field are Irving Penn and Cecil Beaton, photographers of the fashionable rich; Richard Avedon, who achieved fame as a glamour and fashion photographer; and Helmut Newton, controversial fashion and portrait photographer whose work is frequently overtly erotic.
Art Photography
The pioneering work of Daguerre and Talbot led to two distinct types of early photography. The direct positive daguerreotype, prized for its sharpness of detail, was widely used for family portraits, as a substitute for the far more expensive painted portrait. Later, the daguerreotype was supplanted in popularity by the even more inexpensive tintype, which used thin iron sheets instead of glass plates. Talbot's calotype process, on the other hand, was less precise in detail but had the advantage that it produced a negative from which multiple copies could be made. Although the calotype was primarily associated with view photography, a notable use of the process for portraiture was made from 1843 to 1848 by Scottish photographers David Octavius Hill and Robert Adamson. Commissioned to do a group portrait of Scottish clergymen, Hill enlisted Adamson's aid in making a series of photographic studies on which eventually to base his painting. These photographs are today valued as masterful revelations of character and of contemporary life.
Photography as an Alternative Art Form
From the 1860s through the 1890s photography was conceived of as an alternative to drawing and painting. The earliest critical standards applied to photographs were, therefore, those used for judging art, and it was accepted that the camera would be of great use to artists because it could catch details more quickly and with greater fidelity than the eye and hand; in other words, photography was viewed as a shortcut to art—as Hill and Adamson had employed it. Indeed, by the 1870s it was accepted practice to pose subjects carefully in the studio and to retouch and tint photographs to make them more like paintings. An interesting parallel to this exists in the practice of Indian photographers from the time photography was introduced into India in the 1840s. As revealed in a U.S. exhibition, "Through Indian Eyes" (1982), they posed their subjects and manipulated their prints (largely portraits) to make them resemble Indian miniature paintings, obliterating indications of Western canons of space and perspective and painting in ornate backgrounds.
Swedish photographer Oscar Gustave Rejlander and English photographer Henry Peach Robinson pioneered the method of creating one print from several different negatives in the middle and late 1800s. Robinson, originally trained as an artist, based his composite, storytelling images on preliminary pencil sketches. His influence as an art photographer was pervasive. For example, some of the works of his compatriot Julia Margaret Cameron—a series of allegorical tableaus—were posed and costumed in emulation of contemporary painting styles.
Photography in Its Own Right
Cameron's portrait studies are close-up, dramatically lighted photographs of her friends—members of English literary and scientific circles—and are powerful revelations of character. The work of Nadar (the professional name of Gaspard Félix Tournachon, a French caricaturist who became a photographer) is another noteworthy exception to contemporary artificiality. His cartes-de-visite (mounted photographs the size of calling cards) are a series of simply posed, incisively direct portraits of Parisian intelligentsia. Shot against plain backgrounds, with diffused light to bring out details, these photographs are examples of Nadar's powers of observation.
An interesting reversal of the early pattern of art influencing photography occurred with the work of English-American photographer Eadweard Muybridge. His sequence of shots of animals and people in motion revealed to artists and scientists physiological details previously unobserved. American painter Thomas Eakins also experimented with motion photography, although primarily as a reference tool for figure painting.
The approach to photography as a substitute for the visual arts was challenged by English photographer Peter Henry Emerson, who urged photographers to turn directly to nature for inspiration and to limit their manipulation of inherent photographic processes. His book Naturalistic Photography for Students of the Art (1889) was based on his belief that photography is an art in itself, independent of painting. Later, he modified this statement, theorizing that mere reproduction of nature is not art. Emerson's other writings—distinguishing art photography from photographs produced for nonaesthetic purposes, and discussing the arrangement of photographic exhibitions—further defined the art aspect of photography.
Photo-Secession
As a judge of an amateur photographic competition in 1887, Emerson awarded a prize to Alfred Stieglitz, an American photographer then studying abroad, whose work exemplified Emerson's own views. Stieglitz returned to the United States in 1890 and made a series of straightforward pictures of New York City in different seasons and weather conditions. In 1902 he founded the Photo-Secession movement, which championed photography as an independent art form. Members of the group included Americans Gertrude Käsebier, Edward Steichen, Clarence White, and many others. Their official publication was the superbly produced Camera Work (1903-1917). After the Photo-Secessionists disbanded, Stieglitz continued to foster new talent through exhibitions at his gallery, 291, at 291 Fifth Avenue in New York City. Those whose works were shown there included American photographers Paul Strand, Edward Weston, Ansel Adams, and Imogen Cunningham.
Before World War I (1914-1918), Stieglitz, Steichen, and Strand had used soft focus and printed their photographs on paper with a special texture in order to produce impressionistic images reminiscent both of Japanese prints and the atmospheric paintings of American artist J.A.M. Whistler. In the 1920s, however, they turned to capturing minute details and abstracting natural forms, with precision and deep emotional effect. Steichen, in particular, turned to portraiture. They wanted, as Strand wrote, to free "the photograph from the domination of painting."
Some of Strand's work was published by Stieglitz in the last two issues of Camera Work. They represent a break with the traditional subject matter of art photography and a move toward recognizing the aesthetic value of everyday objects. A few years later, German photographer Albert Renger-Patzsch, working independently, reached the same conclusion. In 1922 Renger-Patzsch began making close-up photographs of natural and manufactured objects.
Manipulative Photography
Photography had not freed itself entirely from the influence of painting, however. In Europe in the 1920s the rebellious notions of the Dada movement found expression in art photography in the work of the artists László Moholy-Nagy of Hungary and Man Ray of the United States, both of whom employed the manipulative approach. For their photograms or "Rayographs" they even dispensed with the camera itself, making abstract images by arranging objects on light-sensitive surfaces. They also experimented with solarized prints, a method of reexposing a print to light during the developing process, resulting in partial or total reversal of black and white tones and exaggerated outlines. As photography had originally freed painting from its traditional role of recording visual facts, new principles adapted from Dada and surrealist painting and from collage released art photography from simple, nonmanipulative techniques.
Straight Photography
At the same time, however, there remained a group of American photographers who, following Stieglitz, pursued straight—that is, nonmanipulative—photography. In the 1930s several California photographers formed an informal society called Group f/64 (f/64 is the diaphragm aperture on a lens that gives great depth of field). The members of Group f/64, who included Weston, Adams, and Cunningham, shared the belief that photographers should exploit the inherent, unique capabilities of the camera to produce an image capturing faraway details in as sharp focus as objects close at hand. These photographers produced straightforward images of natural objects, people, and landscapes. Adams was preeminently the photographer of the effects of light on scenery of the western United States. Weston and Cunningham were more concerned with abstract natural forms.
Recent Trends
Several trends have developed—most noticeably in the United States—since the 1950s, as the distinction between documentary and art photography has become less clear. A tendency toward introspection characterized the work of such photographers as Americans Minor White and Aaron Siskind. They used photographs as "equivalents" (Stieglitz's description of his own late work) of personal emotions and thoughts. Other photographers, such as Swiss-born Robert Frank and American Garry Winogrand, became concerned with the social landscape. The photographs in Frank's book The Americans (1959) comment ironically on modern life in the United States.
A third trend is toward manipulative photography. Beginning in the early 1960s, drastic experiments in manipulative photography tended more and more to the impersonal and abstract. Many of the printing devices used in the very early years of photography—such as making composite prints, retouching, and painting over photographs—have been revived. American examples include the "phototransformations" of Greek-born artist Lucas Samaras, the eerie, dreamlike images formed from multiple negatives characteristic of photographer Jerry Uelsmann, and the expressionist, disturbing images of photographer Cindy Sherman. Other sorts of manipulation are seen in the work of American photographer William Wegman, who coaxed his dog, Man Ray, into an extraordinary series of attitudes for his book Man's Best Friend (1982). In another direction, neorealist painters have incorporated actual photographs in many of their paintings. See Modern Art and Architecture; Painting.
The work of color photographers is beginning to overcome the earlier critical prejudice against the use of color in art photography. These photographers include American Eliot Porter, known for his exquisite landscapes; Marie Cosindas, who has created elegant and haunting still lifes and portraits with Polaroid color material; William Eggleston, noted for his vibrant images of commonplace subjects; and Stephen Shore, known for his urban landscapes.
Recognition of Photography as an Art Form
Photography is now firmly established as an art medium. A growing number of schools offer undergraduate and graduate degrees in fine arts with an emphasis on photography. Original photographic prints are sold to collectors by galleries, and photographs (as well as pieces of photographic equipment) of historical interest come up for sale regularly at auctions. Critical essays on photography and histories of its development, as well as books reproducing the work of leading photographers, are published in great numbers each year. Periodicals devoted to photography as an art (as opposed to instructional magazines for the hobbyist or professional) publish studies of the aesthetics of photography. Major museums throughout the world have extensive photographic collections, and special museums also exist, such as the International Museum of Photography in Rochester, New York; the International Center of Photography in New York City; the Museum of Photographic Arts in San Diego, California; and the Museum of Photography in Riverside, California.
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