Photography is the process of making pictures by means of capturing light on a light-sensitive medium, such as a sensor or film. Light patterns reflected or emitted from objects are recorded onto a sensitive medium or storage chip through a timed exposure. The process is done through mechanical, chemical or digital devices known as cameras.

Lens and mounting of a large-format camera

The word comes from the Greek words φως phos ("light"), and γραφίς graphis ("stylus", "paintbrush") or γραφή graphê, together meaning "drawing with light" or "representation by means of lines" or "drawing." Traditionally the product of photography has been called a photograph. The term photo is an abbreviation; many people also call them pictures. In digital photography, the term image has begun to replace photograph. (The term image is traditional in geometric optics.)

[edit] Photographic image-forming devices

The camera or camera obscura is the image-forming device and photographic film or a digital storage card is the recording medium, although other methods are available. For instance, the photocopy or xerography machine forms permanent images but uses the transfer of static electrical charges rather than photographic film, hence the term electrophotography. Rayographs published by Man Ray and others are images produced by the shadows of objects cast on the photographic paper, without the use of a camera. Objects can also be placed directly on the glass of a scanner to produce digital pictures.

Photographers control the camera and lens to "expose" the light recording material (usually film or a charge-coupled device; a complementary metal-oxide-semiconductor may also be used) to the required amount of light. After processing, this produces an image.

The controls usually include but are not limited to:

• Focus of the lens
• Aperture of the lens - adjustment of the iris, measured as f-number, which controls the amount of light entering the lens. Aperture also has an effect on focus and depth of field.
• Shutter speed - adjustment of the speed (often expressed either as fractions of seconds or as an angle, with mechanical shutters) of the shutter to control the amount of time during which the imaging medium is exposed to light per each exposure. Shutter speed may be used to control the amount of light striking the image plane, though doing so has implications for the amount of motion blur visible in the exposed image.
• White balance - on digital cameras, electronic compensation for the color temperature associated with a given set of lighting conditions, ensuring that white light is registered as such on the imaging chip and therefore that the colors in the frame will appear natural. On mechanical, film-based cameras, this function is served by the operator's choice of film stock. In addition to using white balance to register natural coloration of the image, photographers may employ white balance to aesthetic end, for example white balancing to a blue object in order to obtain a warm color temperature.
• Metering - measurement of exposure at a midtone so that highlights and shadows are exposed according to the photographer's wishes. Many modern cameras feature this ability, though it is traditionally accomplished with the use of a separate light metering device.
• ISO speed - traditionally used to set the film speed of the selected film on film cameras, ISO speeds are employed on modern digital cameras as an indication of the system's gain from light to numerical output and to control the automatic exposure system. With a correct combination of ISO speed, aperture, and shutter speed, the makes an image that is neither too dark nor too light.
• Auto-focus point - on some cameras, the selection of a point in the imaging frame upon which the auto-focus system will attempt to focus. Many SLR cameras feature multiple auto-focus points in the viewfinder.

Many other elements of the imaging device itself may have a pronounced effect on the quality and/or aesthetic effect of a given photograph; among them are:

• Focal length and type of lens (telephoto, macro, wide angle, or zoom)
• Filters or scrims placed between the subject and the light recording material, either in front of or behind the lens
• Inherent sensitivity of the medium to light intensity and color/wavelengths.
• The nature of the light recording material, for example its resolution as measured in pixels or grains of silver halide.

Remembering Camera controls are inter-related, as the total amount of light reaching the film plane (the "exposure") changes proportionately with the duration of exposure, aperture of the lens, and focal length of the lens (which changes as the lens is focused, or zoomed). Changing any of these controls alters the exposure. Many consumer-grade cameras may be set to adjust most or all of these controls automatically, with little or no input from the operator. This automatic functionality may be useful to amateur photographers, who may not have mastered the ability to expose their photographs manually.

The duration of an exposure is referred to as shutter speed, often even in cameras that don't have a physical shutter, and is typically measured in fractions of a second. Aperture is expressed by an f-number or f-stop (derived from focal ratio), which is proportional to the ratio of the focal length to the diameter of the aperture. If the f-number is decreased by a factor of , the aperture diameter is increased by the same factor, and its area is increased by a factor of 2. The f-stops that might be found on a typical lens include 2.8, 4, 5.6, 8, 11, 16, 22, 32, where going up "one stop" doubles the amount of light reaching the film, and stopping down one stop halves the amount of light.

Exposures can be achieved through various combinations of shutter speed and aperture. For example, f/8 at 1/125th of a second and f/4 at 1/500th of a second yield the same amount of light. The chosen combination has an impact on the final result. In addition to the subject or camera movement that might vary depending on the shutter speed, the aperture (and focal length of the lens) determine the depth of field, which refers to the range of distances from the lens that will be in focus. For example, using a long lens and a large aperture (f/2.8, for example), a subject's eyes might be in sharp focus, but not the tip of the nose. With a smaller aperture (f/22), or a shorter lens, both the subject's eyes and nose can be in focus. With very small apertures, such as pinholes, a wide range of distance can be brought into focus.

Image capture is only part of the image forming process. Regardless of material, some process must be employed to render the latent image captured by the camera into the final photographic work. This process consists of two steps, development, and printing.

During the printing process, modifications can be made to the print by several controls. Many of these controls are similar to controls during image capture, while some are exclusive to the printing process. Most controls have equivalent digital concepts, but some create different effects. For example, dodging and burning controls are different between digital and film processes. Other printing modifications include:

• Chemicals and process used during film development
• Duration of exposure — equivalent to shutter speed
• Printing aperture — equivalent to aperture, but has no effect on depth of field
• Contrast
• Dodging — reduces exposure of certain print areas, resulting in a lighter areas
• Burning — increases exposure of certain areas, resulting in darker areas
• Paper quality — glossy, matte, etc

[edit] Uses of photography

Photography gained the interest of many scientists and artists from its inception. Scientists have used photography to record and study movements, such as Eadweard Muybridge's study of human and animal locomotion in 1887. Artists are equally interested by these aspects but also try to explore avenues other than the photo-mechanical representation of reality, such as the pictorialist movement. Military, police and security forces use photography for surveillance, recognition and data storage. Photography is used to preserve memories of favorites and as a source of entertainment.

[edit] History of photography

Nicéphore Niépce's earliest surviving photograph, c. 1826

[edit] Chemical photography

For centuries images have been projected onto surfaces. As argued by artist David Hockney, some artists used the camera obscura and camera lucida to trace scenes as early as the 16th century. However, this theory is heavily disputed by today's contemporary realist artists who find the device almost impossible to use. Furthermore, these artists are able to produce work of extremely realistic and accurate quality using techniques of measurement and observation passed down in generations old traditions, and not any sort of tracing. These traditions were used by the old masters in their lineage and it is not plausible that the camera obscura would have been widely used, as other freehand techniques are more accurate and very easy to use with proper training. These early cameras did not fix an image, but only projected images from an opening in the wall of a darkened room onto a surface, turning the room into a large pinhole camera. The phrase camera obscura literally means darkened room. While this early prototype of today's modern camera may have had modest usage in its time, it was an important step in the evolution of the invention.

The first photograph was an image produced in the 1820s by the French inventor Nicéphore Niépce on a polished pewter plate covered with a petroleum derivative called bitumen of Judea. Produced with a camera, the image required an eight-hour exposure in bright sunshine. Niépce then began experimenting with silver compounds based on a Johann Heinrich Schultz discovery in 1724 that a silver and chalk mixture darkens when exposed to light.

"Boulevard du Temple", taken by Daguerre in late 1838 or early 1839, was the first ever photograph of a person. It is an image of a busy street, but because exposure time was over ten minutes, the city traffic was moving too much to appear. The exception is a man in the bottom left corner, who stood still getting his boots polished long enough to show. (click photo to enlarge)

In partnership, Niépce, in Chalon-sur-Saône, and Louis Daguerre, in Paris, refined the existing silver process. In 1833 Niépce died of a stroke, leaving his notes to Daguerre. While he had no scientific background, Daguerre made two pivotal contributions to the process. He discovered that exposing the silver first to iodine vapour, before exposure to light, and then to mercury fumes after the photograph was taken, could form a latent image. Bathing the plate in a salt bath then fixes the image. In 1839 Daguerre announced that he had invented a process using silver on a copper plate called the Daguerreotype. A similar process is still used today for Polaroids. The French government bought the patent and immediately made it public domain.

In 1832, French-Brazilian painter and inventor Hercules Florence had already created a very similar process, naming it Photographie, and William Fox Talbot had earlier discovered another means to fix a silver process image but had kept it secret. After reading about Daguerre's invention, Talbot refined his process so that it might be fast enough to take photographs of people. By 1840, Talbot had invented the calotype process. He coated paper sheets with silver chloride to create an intermediate negative image. Unlike a daguerreotype a calotype negative could be used to reproduce positive prints, like most chemical films do today. Talbot patented this process, which greatly limited its adoption. He spent the rest of his life in lawsuits defending the patent until he gave up on photography. Later George Eastman refined Talbot's process, which is the basic technology used by chemical film cameras today. Hippolyte Bayard had also developed a method of photography but delayed announcing it, and so was not recognized as its inventor.

In 1851 Frederick Scott Archer invented the collodion process. Photographer and children's author, Lewis Carroll, used this process.

Slovene Janez Puhar invented the technical procedure for making photographs on glass in 1841. The invention was recognized on July 17 1852 in Paris by the Académie Nationale Agricole, Manufacturière et Commerciale.

Herbert Bowyer Berkeley experimented with his own version of collodian emulsions after Samman introduced the idea of adding dithionite to the pyrogallol developer. Berkeley discovered that with his own addition of sulphite, to absorb the sulphur dioxide given off by the chemical dithionite in the developer, that dithionite was not required in the developing process. In 1881 he published his discovery. Berkeley's formula contained pyrogallol, sulphite and citric acid. Ammonia was added just before use to make the formula alkaline The new formula was sold by the Platinotype Company in London as Sulpho-Pyrogallol Developer.^[1]

[edit] Reference

• Coe, Brian. The Birth of Photography. Ash & Grant, 1976.

[edit] Popularization

The Daguerreotype proved popular in responding to the demand for portraiture emerging from the middle classes during the Industrial Revolution. This demand, that could not be met in volume and in cost by oil painting, added to the push for the development of photography. Daguerreotypes, while beautiful, were fragile and difficult to copy. A single photograph taken in a portrait studio could cost USD $1,000 in 2006. Photographers also encouraged chemists to refine the process of making many copies cheaply, which eventually led them back to Talbot's process.

Ultimately, the modern photographic process came about from a series of refinements and improvements in the first 20 years. In 1884 George Eastman, of Rochester, New York, developed dry gel on paper, or film, to replace the photographic plate so that a photographer no longer needed to carry boxes of plates and toxic chemicals around. In July of 1888 Eastman's Kodak camera went on the market with the slogan "You press the button, we do the rest". Now anyone could take a photograph and leave the complex parts of the process to others, and photography became available for the mass-market in 1901 with the introduction of Kodak Brownie.

Since then color film has become standard, as well as automatic focus and automatic exposure. Digital recording of images is becoming increasingly common, as digital cameras allow instant previews on LCD screens and the resolution of top of the range models has exceeded high quality 35 mm film while lower resolution models have become affordable. For the enthusiast photographer processing black and white film, little has changed since the introduction of the 35mm film Leica camera in 1925.

[edit] Economic history

A photographer appears to be photographing himself in a 19th century photographic studio., c. 1893

In the nineteenth century, photography developed rapidly as a commercial service. End-user supplies of photographic equipment accounted for only about 20% of industry revenue.

With the development of digital technologies and of communications devices, such as camera phones, understanding the economics of image use is becoming increasingly important for understanding the evolution of the communications industry as a whole.

[edit] Resources

Jenkins, Reese V. Images & Enterprise: Technology and the American Photographic Industry 1839-1925. Baltimore, The Johns Hopkins University Press, 1975. The book provides an overview of the economics of photography and the development of the Eastman Kodak Company.

[edit] Photography types

[edit] Color photography

Main article: Color photography

Color photography was explored throughout the 1800s. Initial experiments in color could not fix the photograph and prevent the color from fading. The first permanent color photo was taken in 1861 by the physicist James Clerk Maxwell.

Early color photograph taken by Prokudin-Gorskii (1915)

One of the early methods of taking color photos was to use three cameras. Each camera would have a color filter in front of the lens. This technique provides the photographer with the three basic channels required to recreate a color image in a darkroom or processing plant. Russian photographer Sergei Mikhailovich Prokudin-Gorskii developed another technique, with three color plates taken in quick succession.

Practical application of the technique was held back by the very limited color response of early film; however, in the early 1900s, following the work of photo-chemists such as H. W. Vogel, emulsions with adequate sensitivity to green and red light at last became available.

The first color film, Autochrome, invented by the French Lumière brothers, reached the market in 1907. It was based on a 'screen-plate' filter made of dyed dots of potato starch, and was the only color film on the market until German Agfa introduced the similar Agfacolor in 1932. In 1935, American Kodak introduced the first modern ('integrated tri-pack') color film, Kodachrome, based on three colored emulsions. This was followed in 1936 by Agfa's Agfacolor Neue. Unlike the Kodachrome tri-pack process the colour couplers in Agfacolor Neue were integral with the emulsion layers, which greatly simplified the film processing. Most modern color films, except Kodachrome, are based on the Agfacolor Neue technology. Instant color film was introduced by Polaroid in 1963.

As an interesting side note, the inventors of Kodachrome, Leopold Mannes and Leopold Godowsky, Jr. were both accomplished musicians. Godowsky was the brother-in-law of George Gershwin and his father was Leopold Godowsky, one of the world's greatest pianists.

Color photography may form images as a positive transparency, intended for use in a slide projector or as color negatives, intended for use in creating positive color enlargements on specially coated paper. The latter is now the most common form of film (non-digital) color photography owing to the introduction of automated photoprinting equipment.

[edit] Digital Photography

Main article: Digital photography

Nikon digital camera and scanner, which converts film images to digital

Traditional photography burdened photographers working at remote locations without easy access to processing facilities, and competition from television pressured photographers to deliver images to newspapers with greater speed. Photojournalists at remote locations often carried miniature photo labs and a means of transmitting images through telephone lines. In 1981, Sony unveiled the first consumer camera to use a charge-coupled device for imaging, eliminating the need for film: the Sony Mavica. While the Mavica saved images to disk, the images were displayed on television, and the camera was not fully digital. In 1990, Kodak unveiled the DCS 100, the first commercially available digital camera. Although its high cost precluded uses other than photojournalism and professional photography, commercial digital photography was born.

Digital imaging uses an electronic image sensor to record the image as a set of electronic data rather than as chemical changes on film. The primary difference between digital and chemical photography is that analog photography resists manipulation because it involves film, optics and photographic paper, while digital imaging is a highly manipulative medium. This difference allows for a degree of image post-processing that is comparatively difficult in film-based photography, permitting different communicative potentials and applications.

Digital imaging is rapidly replacing film photography in consumer and professional markets. Digital point-and-shoot cameras have become widespread consumer products, outselling film cameras, and including new features such as video and audio recording. Kodak announced in January 2004 that it would no longer produce reloadable 35 mm cameras after the end of that year. This was interpreted as a sign of the end of film photography. However, Kodak was at that time a minor player in the reloadable film cameras market. In January 2006, Nikon followed suit and announced that they will stop the production of all but two models of their film cameras: the low-end Nikon FM10, and the high-end Nikon F6. On May 25, 2006, Canon announced they will stop developing new film SLR cameras.^[2]

Because photography is popularly synonymous with truth ("The camera doesn't lie."), digital imaging has raised many ethical concerns. Many photojournalists have declared they will not crop their pictures, or are forbidden from combining elements of multiple photos to make "illustrations," passing them as real photographs. Many courts will not accept digital images as evidence because of their inherently manipulative nature. Today's technology has made picture editing relatively easy for even the novice photographer.

See also article: Digital versus film photography

[edit] Photography styles

[edit] Commercial photography

The commercial photographic world can be broken down to:

• Advertising photography: photographs made to illustrate a service or product. These images are generally done with an advertising agency, design firm or with an in-house corporate design team.
• Fashion and glamour photography: This type of photography usually incorporates models. Fashion photography emphasizes the clothes or product, glamour emphasizes the model. Glamour photography is popular in advertising and in men's magazines. Models in glamour photography may be nude, but this is not always the case.
• Still life photography usually depicts inanimate subject matter, typically commonplace objects which may be either natural or man-made.
• Editorial photography: photographs made to illustrate a story or idea within the context of a magazine. These are usually assigned by the magazine.
• Photojournalism: this can be considered a subset of editorial photography. Photographs made in this context are accepted as a truthful documentation of a news story.
• Portrait and wedding photography: photographs made and sold directly to the end user of the images.
• Fine art photography: photographs made to fulfill a vision, and reproduced to be sold directly to the customer.
• Landscape photography: photographs of different locations made to be sold to tourists as postcards

The market for photographic services demonstrates the aphorism "one picture is worth a thousand words," which has an interesting basis in the history of photography. Magazines and newspapers, companies putting up Web sites, advertising agencies and other groups pay for photography.

Many people take photographs for self-fulfillment or for commercial purposes. Organizations with a budget and a need for photography have several options: they can assign a member of the organization, hire someone, run a public competition, or obtain rights to stock photographs.

[edit] Photography as an art form

Manual shutter control and exposure settings can achieve unusual results

Classic Alfred Stieglitz photograph, The Steerage shows unique aesthetic of black and white photos.

During the twentieth century, both fine art photography and documentary photography became accepted by the English-speaking art world and the gallery system. In the United States, a handful of curators spent their lives advocating to put photography in such a system, with Alfred Stieglitz, Edward Steichen, John Szarkowski, and Hugh Edwards the most prominent among them.

The aesthetics of photography is a matter that continues to be discussed regularly, especially in artistic circles. Many artists argued that photography was the mechanical reproduction of an image. If photography is authentically art, then photography in the context of art would need redefinition, such as determining what component of a photograph makes it beautiful to the viewer. The controversy began with the earliest images "written with light": Nicéphore Niépce, Louis Daguerre, and others among the very earliest photographers were met with acclaim, but some questioned if it met the definitions and purposes of art.

Clive Bell in his classic essay Art states that only "significant form" can distinguish art from what is not art.