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Example of a single-lens-reflex camera

A camera is a device used to capture still or moving images focused by a lens and preserving those images on light-sensitive film, video tape, or in digital format.


Alphonse Giroux's Dagerrotype camera, 1839.
Eastman Kodak Company (Rochester, New York) Brownie cameras, (l-r) Model 2, 1901, Model 3, 1908

Arguably the first camera of any kind is the camera obscura, a Latin term meaning "dark chamber". In its original form the camera obscura was either a room or a box; a pin hole on one side allowed light to enter, and the laws of optics would transmit the image of whatever was outside to the interior, where it would be projected in true color on the opposite wall, albeit upside-down. About 400 B.C. a Chinese philosopher named Mo-Ti made the first mention of the camera obscura in history.[1] This was followed by unrelated experiments done by Aristotle (Greece, 384-322 BC) and Abu Ali al-Hasan Ibn al-Haitham (Egypt, c.965 - 1039), who both recognized the optical qualities of the device; by 1544 Dutch scientist Reinerus Gemma-Frisius safely used it to observe a solar eclipse.[2] A convex lens was first placed on the opening about 1644, at which point it became a drawing aid for artists and an astronomical device, in addition to its attraction as a public curiosity which lasted to the end of the 19th century.

It was the small, portable box camera obscuras that were popular on both sides of the Atlantic Ocean which led to the creation of the first true camera. In 1827 Joseph Nicephore Niepce of France experimented with bitumen-coated metal plates to produce the first photographic images. Long exposure times (some eight hours in length) as well as the unreliability of the process led to a partnership with Louis Daguerre, who by 1839 was able to create much-shorter exposure times as well as replace the metal plate with light-sensitive coated glass, which was removable from the camera frame and replaced with another, speeding up the process. The daguerreotype was born, ushering the age of modern photography.

In 1888 George Eastman would take the young field of photography to the next level. Founder of the Eastman Kodak Company and inventor of celluloid roll film, he introduced the "Brownie" in 1900, a small box anyone could buy for a dollar, and which came preloaded with enough film for one hundred shots. Agreeing that these new novice photographers would be more interested in taking pictures of everyday life rather than worry about the technicalities of developing the film, the "Brownie" was made to be sent in to the factory after the picture-taking was complete; the developed and printed photos, as well as a fresh roll of film in the camera, were sent back to the customer. "Brownie" sales would skyrocket, and Kodak would go on to become the world's largest producer of photographic film.

The next step would take place in 1937, when Ed Land founded the Polaroid Corporation. Fundamentally different from the Kodak in its design, the Polaroid was made to use the new "instant film" of Land's invention, which was photographic paper drawn between two steel rollers that ruptured a small pod of developing chemicals immediately following the shot and prior to the ejection of the print from the camera; the amount of time from the snapping of the shutter to enjoying a new photograph was less than four minutes. Marketed to young teenagers and their parents as opposed to professional photographers, Land oversaw his Polaroids taking a large market segment away from Kodak.

The era of the hand-held camera didn't last long, though. In the mid-1990s the first digital cameras had appeared. Dispensing of film entirely, these new cameras were convenient, able to be plugged into a computer, and by 2000 were being attached to cell phones. Partially because of this many camera-makers - Polaroid and Kodak among them - have declared bankruptcy.

Parts of a camera


The image-forming device that is the main portion of a camera is the lens, and depending on the camera consists of one to as many as 12 elements. The first cameras were fitted with a single lens consisting of one convex and one concave surface, called a meniscus lens; as camera design improved, so did the lens, and the single lens element was placed within inexpensive pocket cameras where it did produce satisfactory results for amateur photographers. The power of the lens is indicated by the F-number, referred to as the aperture, and is controlled by a series of F-stops which opens or closes a diaphragm within the lens. The speed, or light-gathering power, of the lens is determined by the F-stops, with the smallest number (F/2.0 on many lenses) allowing the greatest amount of light to reach the film or sensor when the shutter is snapped.

The three basic types of lenses which evolved beginning in the early-20th century were wide-angle, normal, and telephoto.


Wide-angle lenses are used to present as wide as possible the image being taken, or where there is a limited amount of distance between the camera and the subject, such as getting a famous bridge in one shot for illustrative purposes, or to photograph the interior of a house for sale. Such lenses are also categorized into three types: "fisheye", ultra-wide and simple wide-angle. "Fisheye" photographic lenses cover an angle of 180° and greater, while the deformation they create is excessive; it gives the finished images a deeply-curved look, hence the name. The ultra-wide-angle photographic lenses have a viewing angle of from about 100° to about 85°, the deformation they cause is easier to control than "fisheye". Wide-angle photographic lenses have a viewing angle of approximately 90° to 60°, their distortion being small, approaching the perspective found in normal lenses.


Normal lenses have a viewing angle of approximately 55° to 35°. These lenses are the most common and are particularly useful for generic photos and photos under low light as they have a large aperture. The "normal" part of the name is from the subject within the image, as the person or object appears normal in size and shape, relative to the background.


Telephoto, or long-focus, lenses are used primarily to bring into focus an object which is otherwise unobtainable due to distance, such as a faraway building or wildlife, and show an enlarged detail over the same area versus a normal lens. They have a viewing angle of 40° to 1°. Telephoto lenses are often large, necessitating the use of a tripod for control.

Mirror lenses are a recent addition to the telephoto category. Barrel-shaped and light due to the inclusion of mirrors, they are essentially a hand-held Cassegrain telescope. The advantages they have over standard lenses are less cost and similar, if not greater, image-gathering ability; their fixed F-stop (F/6 to F/8) limits their use to daylight hours.


Within the camera is a device called the shutter, which is a light-tight, mechanically movable element which lies in front of the film or electronic sensor. When the photographer takes the picture the shutter opens, allowing light to hit the film or sensor for the duration of the preset shutter speed. After exposure, the shutter closes and protects the film or sensor from unwanted light, and will open again during the photographer's next attempt.

Compact, medium format and large format cameras usually have a central, or leaf, shutter with resilient curved slats that open radially for the duration of the exposure. The central shutter can be located in the camera body or inside the lens between the front and rear lens groups. In film-based cameras such as SLRs the focal plane shutter is located in the camera immediately in front of the film plane in the housing. For exposure, it opens similar to a double-curtain in some models or creates a slot in others; both have variable width which is determined by the exposure time. The longer the exposure time, the wider the slot. Some single-lens medium-format SLRs with central shutter lenses also have an additional focal plane shutter which is not meant for image exposure, but only as an aid or auxiliary closure to protect the film from light when focusing or changing a lens.

In the early days of photography exposure times of several seconds to several minutes were required, with the "shutter" simply being the lens cap removed and replaced by the photographer during the exposure time. Prior to the advent of digital cameras, film SLRs have mechanically controlled shutter speeds up to 1/1000 second for focal plane shutters, and up to 1/500 second for the central shutter. The shortest purely mechanical shutter speed is 1/4000 second for the Nikon FM2 of 1982-2001. Longer shutter speeds in the low second range can be found in older cameras with the self-timer mechanism. With electronic shutter control by means of electromagnets and control electronics, modern 35mm cameras achieve the shortest shutter speeds of 1/12,000 second (Minolta Dynax 9xi and Dynax 9) and system cameras up to 1/32000 second (Olympus OM-D E-M1 Mark II), but also automatically controlled times up to 30 seconds and longer are feasible.


The photographer views the composition and focuses on the image via a viewfinder, which may be optical or electronic. In the optical version the viewfinder is either a separate entity from the lens (such as pocket cameras) or is visually connected through the lens (as in SLRs). The electronic viewfinder is a product of modern digital cameras; the image seen through the lens is focused on an LCD or OLED screen fixed to the back of the camera, which has the added benefit of allowing the photographer to hold the camera at arm's length while taking the shot.

Types of cameras

When first manufactured in the 1830's, the oraiginal Daguerrotype camera was a large, heavy unit suitable for professionals only; the size of the glass or tin plates carried with the early photographers ensured very few pictures were taken on a given day. The Brownie allowed the concept of convenience with its smaller, lighter size. Since then the most sophisticated cameras can now fit in a handbag or shirt pocket, able to take thousands of photos that would fit on a space as small as a fingernail. Despite this, all cameras fit within three major groups: fixed-focus or "point-and-shoot"; manual-focus; and motion picture/video cameras.


"Hello Kitty" camera, an example of a fixed-focus camera.

Fixed-focus cameras consist of a single element lens that is "fixed"; i.e. the focus is set during manufacture. In addition the camera has pre-set controls and shutter speed, allowing the user to take a perfectly-focused image merely by peering through the viewfinder, pointing the camera at the subject and pressing the shutter button. This simplicity of action led to the name "point-and-shoot" as a common description for these cameras.

The best-selling camera of any type, fixed-focus cameras have been made to shoot celluloid roll film of differing sizes, the disk film of the late 1970's to 1980's, and instant film. The size of the cameras allowed them to easily slip into pockets when not in use, and the added convenience of digital format beginning in the late 1990's allowed the user to upload finished images to a computer, dispensing with the development process of celluloid film.

Fixed-focus cameras have seen a sales decline from 52 to 44 percent in recent years,[3] ironically from another, more convenient device with a point-and-shoot camera built in: the cell phone. Like the fixed-focus camera, the cell phone camera can be aimed at the subject and a picture taken at the touch of a button; however, the screen of the cell phone is the viewfinder, allowing the user to hold the phone comfortably away from him while aligning the phone for a good image. And since it is a cell phone, the image (or video, as cell phones have that capability) can be immediately sent to anyone worldwide, an advantage that fixed-focus cameras lack.


Graflex, Inc. (Rochester, New York) medium-format "press" cameras; (l-r) 1947 Crown Graphic, 1949 Century Graphic.
Franke & Heidecke Company (Germany) 1960 Rolleiflex 3.5 F Model 3

This type of camera is exactly as the name implies: the photographer must make a physical adjustment to the lens or other part of the camera to get the subject into focus. The oldest film cameras, such as daguerreotypes, and their view camera descendants had a large portion of the camera sliding forward or back (such as on a rail) to adjust the focus. Later models appearing around the turn of the 20th century, such as monorail and field cameras, adjusted the focus by sliding the lens on a rail. In practice, view cameras are large and cumbersome, with tripod mounts a mandatory accessory, but the end result is a highly detailed, very crisp photograph, in part due to the medium and large format film used. One of these cameras, a very portable, medium-format camera nicknamed the "press camera" due to those who used it for newspapers and publications, enjoyed widespread use and popularity throughout much of the 20th century until supplanted by SLRs; photographic enthusiasts still use them for their superior image quality.

London Stereoscopic Company of London produced the first model of a "twin-lens reflex" camera for commercial distribution in 1885. What this meant for photographers was a more convenient way to take photographs: two lenses were pointed at the subject; one lens on a direct path from the subject to the film; the other acting as a viewfinder, and the photographer operating a single dial to bring both into focus prior to the shutter being snapped. Despite some flaws, such as a mechanical mirror which flipped out of the way when the shutter was released, causing blurs onto some pictures, this type of camera was considered a revolution in photography, leading to smaller sizes to rival the Brownie and one of the best cameras ever marketed: 1929's Rolleiflex, by the Franke & Heidecke Company of Germany.

TLR cameras have both advantages and disadvantages over competing designs. They used type 120 or 220 roll film and expose negatives in 6 × 6 format, with some smaller models using 127 roll film and with an image format of 4 cm × 4 cm. The fixed mirror is simpler and cheaper than elaborate oscillating mirror designs of single-lens reflex cameras and still allows, in contrast to point-and-shoot cameras, the assessment of the focal plane. Due to the lack of mirror mechanics, these cameras are very quiet in operation and work largely vibration-free. In addition, the viewfinder image remains visible during the recording, so that the photographer has full control of what is happening at all times, such as when the photographer blinks when taking a picture. The viewfinder itself is large enough to be viewed with both eyes, which simplifies the picture composition; its placement on top of the camera forces the photographer to look downwards into it, seemingly away from the subject being taken, adding the benefit of going virtually unnoticed. The design of the camera was compact and lightweight, making it ideal for travel photography.

Lack of interchangeable lenses, filter use, reversed-image when viewing, and most notably viewfinder parallax are seen as the disadvantages of the TLR, which enjoyed great popularity in the first half of the 20th century, and resulted in other manufacturers making equally good copies of the original Rolleiflex.

See also