Digital camera

A digital camera is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. While there are still dedicated digital cameras, many more cameras are now incorporated into mobile devices like smartphones, which can, among many other purposes, use their cameras to initiate live video-telephony and directly edit and upload images to others. High-end, high-definition dedicated cameras are still commonly used by professionals and those who desire to take higher-quality photographs.
Digital and digital movie cameras share an optical system, typically using a lens with a variable diaphragm to focus light onto an image pickup device. The diaphragm and shutter admit the correct amount of light to the image, just as with film but the image pickup device is electronic rather than chemical. However, unlike film cameras, digital cameras can display images on a screen immediately after being recorded, and store and delete images from memory. Many digital cameras can also record moving videos with sound. Some digital cameras can crop and stitch pictures and perform other elementary image editing.
History.
The basis for digital camera image sensors is metal–oxide–semiconductor (MOS) technology, which originates from the invention of the MOSFET (MOS field-effect transistor) by Mohamed M. Atalla and Dawon Kahng at Bell Labs in 1959. This led to the development of digital semiconductor image sensors, including the charge-coupled device (CCD) and later the CMOS sensor. The first semiconductor image sensor was the charge-coupled dlol, invented by Willard S. Boyle and George E. Smith at Bell Labs in 1969, based on MOS capacitor technology. The NMOS active-pixel sensor was later invented by Tsutomu Nakamura's team at Olympus in 1985, which led to the development of the CMOS active-pixel sensor (CMOS sensor) by Eric Fossum's team at the NASA Jet Propulsion Laboratory in 1993.
In the 1960s, Eugene F. Lally of the Jet Propulsion Laboratory was thinking about how to use a mosaic photosensor to capture digital images. His idea was to take pictures of the planets and stars while travelling through space to give information about the astronauts' position. As with Texas Instruments employee Willis Adcock's film-less camera (US patent 4,057,830) in 1972, the technology had yet to catch up with the concept.
The Cromemco Cyclops was an all-digital camera introduced as a commercial product in 1975. Its design was published as a hobbyist construction project in the February 1975 issue of "Popular Electronics" magazine. It used a 32×32 metal-oxide-semiconductor (MOS) image sensor, which was a modified MOS dynamic RAM (DRAM) memory chip.
Steven Sasson, an engineer at Eastman Kodak, invented and built a self-contained electronic camera that used a charge-coupled device (CCD) image sensor in 1975. Around the same time, Fujifilm began developing CCD technology in the 1970s. Early uses were mainly military and scientific; followed by medical and news applications.
Practical digital cameras were enabled by advances in data compression, due to the impractically high memory and bandwidth requirements of uncompressed images and video. The most important compression algorithm is the discrete cosine transform (DCT), a lossy compression technique that was first proposed by Nasir Ahmed while he was working at the University of Texas in 1972. Practical digital cameras were enabled by DCT-based compression standards, including the H.26x and MPEG video coding standards introduced from 1988 onwards, and the JPEG image compression standard introduced in 1992.
Nikon was interested in digital photography since the mid-1980s. In 1986, while presenting to Photokina, Nikon introduced an operational prototype of the first SLR-type electronic camera (Still Video Camera), manufactured by Panasonic. The Nikon SVC was built around a sensor 2/3 " charge-coupled device of 300,000 pixels. Storage media, a magnetic floppy disk inside the camera allows recording 25 or 50 B&W images, depending of the definition. In 1988, Nikon released the first commercial electronic single-lens reflex camera, the QV-1000C.
At Photokina 1988, Fujifilm introduced the FUJIX DS-1P, the first fully digital camera, capable of saving data to a semiconductor memory card. The camera's memory card had a capacity of 2 MB of SRAM (static random-access memory), and could hold up to ten photographs. In 1989, Fujifilm released the FUJIX DS-X, the first fully digital camera to be commercially released. In 1996, Toshiba's 40 MB flash memory card was adopted for several digital cameras.
The first commercial camera phone was the Kyocera Visual Phone VP-210, released in Japan in May 1999. It was called a "mobile videophone" at the time, and had a 110,000-pixel front-facing camera. It stored up to 20 JPEG digital images, which could be sent over e-mail, or the phone could send up to two images per second over Japan's Personal Handy-phone System (PHS) cellular network. The Samsung SCH-V200, released in South Korea in June 2000, was also one of the first phones with a built-in camera. It had a TFT liquid-crystal display (LCD) and stored up to 20 digital photos at 350,000-pixel resolution. However, it could not send the resulting image over the telephone function, but required a computer connection to access photos. The first mass-market camera phone was the J-SH04, a Sharp J-Phone model sold in Japan in November 2000. It could instantly transmit pictures via cell phone telecommunication. By the mid-2000s, higher-end cell phones had an integrated digital camera. By the beginning of the 2010s, almost all smartphones had an integrated digital camera.
Image sensors.
The two major types of digital image sensor are CCD and CMOS. A CCD sensor has one amplifier for all the pixels, while each pixel in a CMOS active-pixel sensor has its own amplifier. Compared to CCDs, CMOS sensors use less power. Cameras with a small sensor use a back-side-illuminated CMOS (BSI-CMOS) sensor. The image processing capabilities of the camera determine the outcome of the final image quality much more than the sensor type.
Sensor resolution.
The resolution of a digital camera is often limited by the image sensor that turns light into discrete signals. The brighter the image at a given point on the sensor, the larger the value that is read for that pixel.
Depending on the physical structure of the sensor, a color filter array may be used, which requires demosaicing to recreate a full-color image. The number of pixels in the sensor determines the camera's "pixel count".
In a typical sensor, the pixel count is the product of the number of rows and the number of columns. For example, a 1,000 by 1,000 pixel sensor would have 1,000,000 pixels, or 1 megapixel.
Resolution options.
Firmwares' resolution selector allows the user to optionally lower the resolution, to reduce the file size per picture and extend lossless digital zooming. 
A lower resolution extends the number of remaining photos in free space, postponing the exhaustion of space storage, which is of use where no further data storage device is available, and for captures of lower significance, where the benefit from less space storage consumption outweighs the disadvantage from reduced detail.
Image sharpness.
The final quality of an image depends on all optical transformations in the chain of producing the image.
Batteries.
Digital cameras have become smaller over time, resulting in an ongoing need to develop a [[battery (electricity)|battery]] small enough to fit in the camera and yet able to power it for a reasonable length of time.
Digital cameras utilize either proprietary or standard consumer batteries. , most cameras use proprietary lithium-ion batteries while some use standard AA batteries or primarily use a proprietary Lithium-ion rechargeable battery pack but have an optional AA battery holder available.
Proprietary.
The most common class of battery used in digital cameras is proprietary battery formats. These are built to a manufacturer's custom specifications. Almost all proprietary batteries are lithium-ion. In addition to being available from the [[Original Equipment Manufacturer|OEM]], aftermarket replacement batteries are commonly available for most camera models.
Standard consumer batteries.
Digital cameras that utilize off-the-shelf batteries are typically designed to be able to use both single-use [[primary cell|disposable]] and [[rechargeable batteries]], but not with both types in use at the same time. The most common off-the-shelf battery size used is [[AA battery|AA]]. CR2, [[CR-V3]] batteries, and [[AAA battery|AAA batteries]] are also used in some cameras. The CR2 and CR-V3 batteries are [[lithium battery|lithium based]], intended for a single use. Rechargeable [[RCR-V3]] lithium-ion batteries are also available as an alternative to non-rechargeable CR-V3 batteries.
Some [[battery grip]]s for DSLRs come with a separate holder to accommodate AA cells as an external power source.
Conversion of film cameras to digital.
[[File:Reflex camera numeric.svg|thumb|[[Digital single-lens reflex camera]]]]
When digital cameras became common, many photographers asked whether their [[film camera]]s could be converted to digital. The answer was not immediately clear, as it differed among models. For the majority of 35 mm film cameras the answer is no, the reworking and cost would be too great, especially as lenses have been evolving as well as cameras. For most a conversion to digital, to give enough space for the electronics and allow a liquid crystal display to preview, would require removing the back of the camera and replacing it with a custom built digital unit.
Many early professional SLR cameras, such as the [[Kodak DCS]] series, were developed from 35 mm film cameras. The technology of the time, however, meant that rather than being digital "backs" the bodies of these cameras were mounted on large, bulky digital units, often bigger than the camera portion itself. These were factory built cameras, however, not [[Aftermarket (merchandise)|aftermarket]] conversions.
A notable exception is the [[Nikon E2]] and [[Nikon E3]], using additional optics to convert the [[35 mm format]] to a 2/3 CCD-sensor.
A few 35 mm cameras have had [[digital camera back]]s made by their manufacturer, Leica being a notable example. [[Medium format (film)|Medium format]] and [[large format]] cameras (those using film stock greater than 35 mm), have a low unit production, and typical digital backs for them cost over $10,000. These cameras also tend to be highly modular, with handgrips, film backs, winders, and lenses available separately to fit various needs.
The very large sensor these backs use leads to enormous image sizes. For example, Phase One's P45 39 MP image back creates a single TIFF image of size up to 224.6 MB, and even greater pixel counts are available. Medium format digitals such as this are geared more towards studio and [[portrait photography]] than their smaller DSLR counterparts; the [[ISO speed]] in particular tends to have a maximum of 400, versus 6400 for some DSLR cameras. (Canon EOS-1D Mark IV and [[Nikon D3S]] have ISO 12800 plus Hi-3 ISO 102400 with the Canon EOS-1Dx's ISO of 204800).
Digital camera backs.
In the industrial and high-end professional photography market, some camera systems use modular (removable) image sensors. For example, some medium format SLR cameras, such as the Mamiya 645D series, allow installation of either a digital camera back or a traditional photographic film back.
Linear array cameras are also called scan backs.
Most earlier digital camera backs used linear array sensors, moving vertically to [[digitize]] the image. Many of them only capture [[grayscale]] images. The relatively long exposure times, in the range of seconds or even minutes generally limit scan backs to studio applications, where all aspects of the photographic scene are under the photographer's control.
Some other camera backs use CCD arrays similar to typical cameras. These are called single-shot backs.
Since it is much easier to manufacture a high-quality linear CCD array with only thousands of pixels than a CCD matrix with millions, very high resolution linear CCD camera backs were available much earlier than their CCD matrix counterparts. For example, you could buy an (albeit expensive) camera back with over 7,000 pixel horizontal resolution in the mid-1990s. However, , it is still difficult to buy a comparable CCD matrix camera of the same resolution. Rotating line cameras, with about 10,000 color pixels in its sensor line, are able, , to capture about 120,000 lines during one full 360 degree rotation, thereby creating a single digital image of 1,200 Megapixels.
Most modern digital camera backs use CCD or CMOS matrix sensors. The matrix sensor captures the entire image frame at once, instead of incrementing scanning the frame area through the prolonged exposure. For example, [[Phase One (company)|Phase One]] produces a 39 million pixel digital camera back with a 49.1 x 36.8 mm CCD in 2008. This CCD array is a little smaller than a frame of [[120 film]] and much larger than a [[35mm format|35 mm]] frame (36 x 24 mm). In comparison, consumer digital cameras use arrays ranging from 36 x 24 mm (full frame on high end consumer DSLRs) to 1.28 x 0.96 mm (on camera phones) CMOS sensor.
External links.
[[Category:Digital cameras| ]]
[[Category:Cameras| ]]
[[Category:American inventions]]
[[Category:Audiovisual introductions in 1975]]
[[Category:1975 in the arts]]
[[Category:1975 in technology]]
[[Category:Computer-related introductions in 1975]]
[[Category:20th-century inventions]]