Photography (pronounced /fәˈtɒɡrәfi/ ) is the process, activity and art of creating still or moving pictures by recording radiation on a sensitive medium, such as a photographic film, or an electronic sensor. Light patterns reflected or emitted from objects activate a sensitive chemical or electronic sensor during a timed exposure, usually through a photographic lens in a device known as a camera that also stores the resulting information chemically or electronically. Photography has many uses for business, science, art and pleasure.
The word "photograph" was coined in 1839 by Sir John Herschel and is based on the Greek φῶς ( phos ) "light" and γραφή ( graphê ) "representation by means of lines" or "drawing", together meaning "drawing with light". Traditionally, the products of photography have been called negatives and photographs , commonly shortened to photos .
Function
The camera or camera obscura is the image-forming device, and photographic film or a silicon electronic image sensor is the sensing medium. The respective recording medium can be the film itself, or a digital electronic or magnetic memory.
Photographers control the camera and lens to "expose" the light recording material (such as film) to the required amount of light to form a "latent image" (on film) or "raw file" (in digital cameras) which, after appropriate processing, is converted to a usable image. Digital cameras use an electronic image sensor based on light-sensitive electronics such as charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) technology. The resulting digital image is stored electronically, but can be reproduced on paper or film.
The movie camera is a type of photographic camera which takes a rapid sequence of photographs on strips of film. In contrast to a still camera, which captures a single snapshot at a time, the movie camera takes a series of images, each called a "frame". This is accomplished through an intermittent mechanism. The frames are later played back in a movie projector at a specific speed, called the "frame rate" (number of frames per second). While viewing, a person's eyes and brain merge the separate pictures together to create the illusion of motion.
In all but certain specialized cameras, the process of obtaining a usable exposure must involve the use, manually or automatically, of a few controls to ensure the photograph is clear, sharp and well illuminated. The controls usually include but are not limited to the following:
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 or "long" lens, macro, wide angle, fisheye, or zoom)
- Filters 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.
Exposure and rendering
Camera controls are inter-related. The total amount of light reaching the film plane (the "exposure") changes with the duration of exposure, aperture of the lens, and on the effective focal length of the lens (which in variable focal length lenses, can force a change in aperture as the lens is zoomed). Changing any of these controls can alter the exposure. Many cameras may be set to adjust most or all of these controls automatically. This automatic functionality is useful for occasional photographers in many situations.
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" (using lower f-stop numbers) 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 8 ms (1/125th of a second) and f/5.6 at 4 ms (1/250th of a second) yield the same amount of light. The chosen combination has an impact on the final result. 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. A longer lens or a wider aperture will result in "shallow" depth of field (i.e. only a small plane of the image will be in sharp focus). This is often useful for isolating subjects from backgrounds as in individual portraits or macro photography. Conversely, a shorter lens, or a smaller aperture, will result in more of the image being in focus. This is generally more desirable when photographing landscapes or groups of people. With very small apertures, such as pinholes, a wide range of distance can be brought into focus, but sharpness is severely degraded by diffraction with such small apertures. Generally, the highest degree of "sharpness" is achieved at an aperture near the middle of a lens's range (for example, f/8 for a lens with available apertures of f/2.8 to f/16). However, as lens technology improves, lenses are becoming capable of making increasingly sharp images at wider apertures.
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 a viewable image. With slide film, the developed film is just mounted for projection. Print film requires the developed film negative to be printed onto photographic paper or transparency. Digital images may be uploaded to an image server (e.g., a photo-sharing web site), viewed on a television, or transferred to a computer or digital photo frame.
Prior to the rendering of a viewable image, modifications can be made using several controls. Many of these controls are similar to controls during image capture, while some are exclusive to the rendering process. Most printing 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 print exposure – equivalent to shutter speed
- Printing aperture – equivalent to aperture, but has no effect on depth of field
- Contrast – changing the visual properties of objects in an image to make them distinguishable from other objects and the background
- Dodging – reduces exposure of certain print areas, resulting in lighter areas
- Burning in – increases exposure of certain areas, resulting in darker areas
- Paper texture – glossy, matte, etc
- Paper type – resin-coated (RC) or fiber-based (FB)
- Paper size
- Toners – used to add warm or cold tones to black and white prints
Uses
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 by amateurs to preserve memories of favorite times, to capture special moments, to tell stories, to send messages, and as a source of entertainment.
History
Main article: History of photographyPhotography is the result of combining several technical discoveries. Long before the first photographs were made, Chinese philosopher Mo Ti described a pinhole camera in the 5th century
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