Camera obscura, from a manuscript of military designs. Seventeenth century, possibly Italian.

The history of the camera can be traced much further back than the introduction of photography. Cameras evolved from the camera obscura, and continued to change through many generations of photographic technology, including daguerreotypes, calotypes, dry plates, film, and to the modern day with digital cameras.

Camera obscura

An artist using an 18th-century camera obscura to trace an image

The forerunner to the photographic camera was the camera obscura. Camera obscura (Latin for "dark room") is the natural optical phenomenon that occurs when an image of a scene at the other side of a screen (or for instance a wall) is projected through a small hole in that screen and forms an inverted image (left to right and upside down) on a surface opposite to the opening. The oldest known record of this principle is a description by Han Chinese philosopher Mozi (ca. 470 to ca. 391 BC). Mozi correctly asserted that the camera obscura image is inverted because light travels in straight lines from its source. In the 11th century Arab physicist Ibn al-Haytham (Alhazen)'s wrote very influential books about optics, including experiments with light through a small opening in a darkened room.

The use of a lens in the opening of a wall or closed window shutter of a darkened room to project images used as a drawing aid has been traced back to circa 1550. Since the late 17th century portable camera obscura devices in tents and boxes were used as a drawing aid.

Before the invention of photographic processes there was no way to preserve the images produced by these cameras apart from manually tracing them. The earliest cameras were room-sized, with space for one or more people inside; these gradually evolved into more and more compact models. By Niépce's time portable box camerae obscurae suitable for photography were readily available. The first camera that was small and portable enough to be practical for photography was envisioned by Johann Zahn in 1685, though it would be almost 150 years before such an application was possible.

Early fixed images

The first partially successful photograph of a camera image was made in approximately 1816 by Nicéphore Niépce, using a very small camera of his own making and a piece of paper coated with silver chloride, which darkened where it was exposed to light. No means of removing the remaining unaffected silver chloride was known to Niépce, so the photograph was not permanent, eventually becoming entirely darkened by the overall exposure to light necessary for viewing it. In the mid-1820s, Niépce used a sliding wooden box camera made by Parisian opticians Charles and Vincent Chevalier to experiment with photography on surfaces thinly coated with Bitumen of Judea. The bitumen slowly hardened in the brightest areas of the image. The unhardened bitumen was then dissolved away. One of those photographs has survived.

Daguerreotype camera made by Maison Susse Frères in 1839, with a lens by Charles Chevalier

Daguerreotypes and calotypes

After Niépce's death in 1833, his partner Louis Daguerre continued to experiment and by 1837 had created the first practical photographic process, which he named the daguerreotype and publicly unveiled in 1839.Daguerre treated a silver-plated sheet of copper with iodine vapor to give it a coating of light-sensitive silver iodide. After exposure in the camera, the image was developed by mercury vapor and fixed with a strong solution of ordinary salt (sodium chloride). Henry Fox Talbot perfected a different process, the calotype, in 1840. As commercialized, both processes used very simple cameras consisting of two nested boxes. The rear box had a removable ground glass screen and could slide in and out to adjust the focus. After focusing, the ground glass was replaced with a light-tight holder containing the sensitized plate or paper and the lens was capped. Then the photographer opened the front cover of the holder, uncapped the lens, and counted off as many minutes as the lighting conditions seemed to require before replacing the cap and closing the holder. Despite this mechanical simplicity, high-quality achromatic lenses were standard.

Late 19th century studio camera

Dry plates

Collodion dry plates had been available since 1857, thanks to the work of Désiré van Monckhoven, but it was not until the invention of the gelatin dry plate in 1871 by Richard Leach Maddox that the wet plate process could be rivaled in quality and speed. The 1878 discovery that heat-ripening a gelatin emulsion greatly increased its sensitivity finally made so-called "instantaneous" snapshot exposures practical. For the first time, a tripod or other support was no longer an absolute necessity. With daylight and a fast plate or film, a small camera could be hand-held while taking the picture. The ranks of amateur photographers swelled and informal "candid" portraits became popular. There was a proliferation of camera designs, from single- and twin-lens reflexes to large and bulky field cameras, simple box cameras, and even "detective cameras" disguised as pocket watches, hats, or other objects.

The short exposure times that made candid photography possible also necessitated another innovation, the mechanical shutter. The very first shutters were separate accessories, though built-in shutters were common by the end of the 19th century.

Kodak and the birth of film

Kodak No. 2 Brownie box camera, circa 1910

The use of photographic film was pioneered by George Eastman, who started manufacturing paper film in 1885 before switching to celluloidin 1888-1889. His first camera, which he called the "Kodak," was first offered for sale in 1888. It was a very simple box camera with a fixed-focus lens and single shutter speed, which along with its relatively low price appealed to the average consumer. The Kodak came pre-loaded with enough film for 100 exposures and needed to be sent back to the factory for processing and reloading when the roll was finished. By the end of the 19th century Eastman had expanded his lineup to several models including both box and folding cameras.

In 1900, Eastman took mass-market photography one step further with the Brownie, a simple and very inexpensive box camera that introduced the concept of the snapshot. The Brownie was extremely popular and various models remained on sale until the 1960s.

Film also allowed the movie camera to develop from an expensive toy to a practical commercial tool.

Despite the advances in low-cost photography made possible by Eastman, plate cameras still offered higher-quality prints and remained popular well into the 20th century. To compete with rollfilm cameras, which offered a larger number of exposures per loading, many inexpensive plate cameras from this era were equipped with magazines to hold several plates at once. Special backs for plate cameras allowing them to use film packs or rollfilm were also available, as were backs that enabled rollfilm cameras to use plates.

Except for a few special types such as Schmidt cameras, most professional astrographs continued to use plates until the end of the 20th century when electronic photography replaced them.

35 mm

Leica I, 1925

Argus C3, 1939

A number of manufacturers started to use 35mm film for still photography between 1905 and 1913. The first 35mm cameras available to the public, and reaching significant numbers in sales were the Tourist Multiple, in 1913, and the Simplex, in 1914.

Oskar Barnack, who was in charge of research and development at Leitz, decided to investigate using 35 mm cine film for still cameras while attempting to build a compact camera capable of making high-quality enlargements. He built his prototype 35 mm camera (Ur-Leica) around 1913, though further development was delayed for several years by World War I. It wasn't until after World War I that Leica commercialized their first 35mm Cameras. Leitz test-marketed the design between 1923 and 1924, receiving enough positive feedback that the camera was put into production as the Leica I (for Leitz camera) in 1925. The Leica's immediate popularity spawned a number of competitors, most notably the Contax (introduced in 1932), and cemented the position of 35 mm as the format of choice for high-end compact cameras.

Kodak got into the market with the Retina I in 1934, which introduced the 135 cartridge used in all modern 35 mm cameras. Although the Retina was comparatively inexpensive, 35 mm cameras were still out of reach for most people and rollfilm remained the format of choice for mass-market cameras. This changed in 1936 with the introduction of the inexpensive Argus A and to an even greater extent in 1939 with the arrival of the immensely popular Argus C3. Although the cheapest cameras still used rollfilm, 35 mm film had come to dominate the market by the time the C3 was discontinued in 1966.

The fledgling Japanese camera industry began to take off in 1936 with the Canon 35 mm rangefinder, an improved version of the 1933 Kwanon prototype. Japanese cameras would begin to become popular in the West after Korean War veterans and soldiers stationed in Japan brought them back to the United States and elsewhere.

TLRs and SLRs

A historic camera: the Contax S of 1949 — the first pentaprism SLR

Asahiflex IIb, 1954

Nikon F of 1959 — the first Japanese system camera

The first practical reflex camera was the Franke & Heidecke Rolleiflex medium format TLR of 1928. Though both single- and twin-lens reflex cameras had been available for decades, they were too bulky to achieve much popularity. The Rolleiflex, however, was sufficiently compact to achieve widespread popularity and the medium-format TLR design became popular for both high- and low-end cameras.

A similar revolution in SLR design began in 1933 with the introduction of the Ihagee Exakta, a compact SLR which used 127 rollfilm. This was followed three years later by the first Western SLR to use 135 film, the Kine Exakta (World's first true 35mm SLR was Soviet "Sport" camera, marketed several months before Kine Exakta, though "Sport" used its own film cartridge). The 35mm SLR design gained immediate popularity and there was an explosion of new models and innovative features after World War II. There were also a few 35mm TLRs, the best-known of which was the Contaflex of 1935, but for the most part these met with little success.

The first major post-war SLR innovation was the eye-level viewfinder, which first appeared on the Hungarian Duflex in 1947 and was refined in 1948 with the Contax S, the first camera to use a pentaprism. Prior to this, all SLRs were equipped with waist-level focusing screens. The Duflex was also the first SLR with an instant-return mirror, which prevented the viewfinder from being blacked out after each exposure. This same time period also saw the introduction of the Hasselblad 1600F, which set the standard for medium format SLRs for decades.

In 1952 the Asahi Optical Company (which later became well known for its Pentax cameras) introduced the first Japanese SLR using 135 film, the Asahiflex. Several other Japanese camera makers also entered the SLR market in the 1950s, including Canon, Yashica, and Nikon. Nikon's entry, the Nikon F, had a full line of interchangeable components and accessories and is generally regarded as the first Japanese system camera. It was the F, along with the earlier S series of rangefinder cameras, that helped establish Nikon's reputation as a maker of professional-quality equipment.

Instant cameras

Polaroid Model J66, 1961

While conventional cameras were becoming more refined and sophisticated, an entirely new type of camera appeared on the market in 1948. This was the Polaroid Model 95, the world's first viable instant-picture camera. Known as a Land Camera after its inventor, Edwin Land, the Model 95 used a patented chemical process to produce finished positive prints from the exposed negatives in under a minute. The Land Camera caught on despite its relatively high price and the Polaroid lineup had expanded to dozens of models by the 1960s. The first Polaroid camera aimed at the popular market, the Model 20 Swinger of 1965, was a huge success and remains one of the top-selling cameras of all time.

Automation

The first camera to feature automatic exposure was the selenium light meter-equipped, fully automatic Super Kodak Six-20 pack of 1938, but its extremely high price (for the time) of $225 ($3912 in present terms) kept it from achieving any degree of success. By the 1960s, however, low-cost electronic components were commonplace and cameras equipped with light meters and automatic exposure systems became increasingly widespread.

The next technological advance came in 1960, when the German Mec 16 SB subminiature became the first camera to place the light meter behind the lens for more accurate metering. However, through-the-lens metering ultimately became a feature more commonly found on SLRs than other types of camera; the first SLR equipped with a TTL system was the Topcon RE Super of 1962.

Digital cameras

Digital cameras differ from their analog predecessors primarily in that they do not use film, but capture and save photographs on digital memory cards or internal storage instead. Their low operating costs have relegated chemical cameras to niche markets. Digital cameras now include wireless communication capabilities (for example Wi-Fi or Bluetooth) to transfer, print or share photos, and are commonly found on mobile phones.

Early development

The concept of digitizing images on scanners, and the concept of digitizing video signals, predate the concept of making still pictures by digitizing signals from an array of discrete sensor elements. Early spy satellites used the extremely complex and expensive method of de-orbit and airborne retrieval of film canisters. Technology was pushed to skip these steps through the use of in-satellite developing and electronic scanning of the film for direct transmission to the ground. The amount of film was still a major limitation, and this was overcome and greatly simplified by the push to develop an electronic image capturing array that could be used instead of film. The first electronic imaging satellite was the KH-11launched by the NRO in late 1976. It had a charge-coupled device (CCD) array with a resolution of 800 x 800 pixels (0.64 megapixels).At Philips Labs in New York, Edward Stupp, Pieter Cath and Zsolt Szilagyi filed for a patent on "All Solid State Radiation Imagers" on 6 September 1968 and constructed a flat-screen target for receiving and storing an optical image on a matrix composed of an array of photodiodes connected to a capacitor to form an array of two terminal devices connected in rows and columns. Their US patent was granted on 10 November 1970. Texas Instruments engineer Willis Adcock designed a filmless camera that was not digital and applied for a patent in 1972, but it is not known whether it was ever built.The Cromemco CYCLOPS introduced as a hobbyist construction project in 1975 was the first digital camera to be interfaced to a microcomputer.

The first recorded attempt at building a self-contained digital camera was in 1975 by Steven Sasson, an engineer at Eastman Kodak. It used the then-new solid-state CCD image sensor chips developed by Fairchild Semiconductor in 1973. The camera weighed 8 pounds (3.6 kg), recorded black and white images to a compact cassette tape, had a resolution of 0.01 megapixels (10,000 pixels), and took 23 seconds to capture its first image in December 1975. The prototype camera was a technical exercise, not intended for production.

Analog electronic cameras

Sony Mavica, 1981

Handheld electronic cameras, in the sense of a device meant to be carried and used like a handheld film camera, appeared in 1981 with the demonstration of the Sony Mavica (Magnetic Video Camera). This is not to be confused with the later cameras by Sony that also bore the Mavica name. This was an analog camera, in that it recorded pixel signals continuously, as videotape machines did, without converting them to discrete levels; it recorded television-like signals to a 2 × 2 inch "video floppy".In essence it was a video movie camera that recorded single frames, 50 per disk in field mode and 25 per disk in frame mode. The image quality was considered equal to that of then-current televisions.

Canon RC-701, 1986

Analog electronic cameras do not appear to have reached the market until 1986 with the Canon RC-701. Canon demonstrated a prototype of this model at the 1984 Summer Olympics, printing the images in the Yomiuri Shinbun, a Japanese newspaper. In the United States, the first publication to use these cameras for real reportage was USA Today, in its coverage of World Series baseball. Several factors held back the widespread adoption of analog cameras; the cost (upwards of $20,000), poor image quality compared to film, and the lack of quality affordable printers. Capturing and printing an image originally required access to equipment such as a frame grabber, which was beyond the reach of the average consumer. The "video floppy" disks later had several reader devices available for viewing on a screen, but were never standardized as a computer drive.

The early adopters tended to be in the news media, where the cost was negated by the utility and the ability to transmit images by telephone lines. The poor image quality was offset by the low resolution of newspaper graphics. This capability to transmit images without a satellite link was useful during the Tiananmen Square protests of 1989 and the first Gulf War in 1991.

US government agencies also took a strong interest in the still video concept, notably the US Navy for use as a real time air-to-sea surveillance system.

The first analog electronic camera marketed to consumers may have been the Casio VS-101 in 1987. A notable analog camera produced the same year was the Nikon QV-1000C, designed as a press camera and not offered for sale to general users, which sold only a few hundred units. It recorded images in greyscale, and the quality in newspaper print was equal to film cameras. In appearance it closely resembled a modern digital single-lens reflex camera. Images were stored on video floppy disks.

Silicon Film, a proposed digital sensor cartridge for film cameras that would allow 35 mm cameras to take digital photographs without modification was announced in late 1998. Silicon Film was to work like a roll of 35 mm film, with a 1.3 megapixel sensor behind the lens and a battery and storage unit fitting in the film holder in the camera. The product, which was never released, became increasingly obsolete due to improvements in digital camera technology and affordability. Silicon Films' parent company filed for bankruptcy in 2001.

Arrival of true digital cameras

The first portable digital SLR camera, introduced by Minolta in 1995.

Nikon D1, 1999

By the late 1980s, the technology required to produce truly commercial digital cameras existed. The first true portable digital camera that recorded images as a computerized file was likely the Fuji DS-1P of 1988, which recorded to a 2 MB SRAM memory card that used a battery to keep the data in memory. This camera was never marketed to the public.

The first digital camera of any kind ever sold commercially was possibly the MegaVision Tessera in 1987 though there is not extensive documentation of its sale known. The first portable digital camera that was actually marketed commercially was sold in December 1989 in Japan, the DS-X by Fuji The first commercially available portable digital camera in the United States was the Dycam Model 1, first shipped in November 1990.It was originally a commercial failure because it was black and white, low in resolution, and cost nearly $1,000 (about $2000 in 2014). It later saw modest success when it was re-sold as the Logitech Fotoman in 1992. It used a CCD image sensor, stored pictures digitally, and connected directly to a computer for download.

In 1991, Kodak brought to market the Kodak DCS (Kodak Digital Camera System), the beginning of a long line of professional Kodak DCSSLR cameras that were based in part on film bodies, often Nikons. It used a 1.3 megapixel sensor, had a bulky external digital storage system and was priced at $13,000. At the arrival of the Kodak DCS-200, the Kodak DCS was dubbed Kodak DCS-100.

The move to digital formats was helped by the formation of the first JPEG and MPEG standards in 1988, which allowed image and video files to be compressed for storage. The first consumer camera with a liquid crystal display on the back was the Casio QV-10 developed by a team led by Hiroyuki Suetaka in 1995. The first camera to use CompactFlash was the Kodak DC-25 in 1996. The first camera that offered the ability to record video clips may have been the Ricoh RDC-1 in 1995.

In 1995 Minolta introduced the RD-175, which was based on the Minolta 500si SLR with a splitter and three independent CCDs. This combination delivered 1.75M pixels. The benefit of using an SLR base was the ability to use any existing Minolta AF mount lens. 1999 saw the introduction of the Nikon D1, a 2.74 megapixel camera that was the first digital SLR developed entirely from the ground up by a major manufacturer, and at a cost of under $6,000 at introduction was affordable by professional photographers and high-end consumers. This camera also used Nikon F-mount lenses, which meant film photographers could use many of the same lenses they already owned.

Digital camera sales continued to flourish, driven by technology advances. The digital market segmented into different categories, Compact Digital Still Cameras, Bridge Cameras, Mirrorless Compacts and Digital SLRs. One of the major technology advances was the development of CMOS sensors, which helped drive sensor costs low enough to enable the widespread adoption of camera phones.

Since 2003, digital cameras have outsold film cameras and Kodak announced in January 2004 that they would no longer sell Kodak-branded film cameras in the developed world - and 2012 filed for bankruptcy after struggling to adapt to the changing industry. Smartphones now routinely include high resolution digital cameras.

[ ALL INFORMATIONS ARE COLLECTED FROM THE INTERNET FOR INFORMATION PURPOSES ONLY ]

A digital single-lens reflex camera (also called a digital SLR or DSLR) is a digital camera that combines the optics and the mechanisms of a single-lens reflex camera with a digital imaging sensor, as opposed to photographic film. The reflex design scheme is the primary difference between a DSLR and other digital cameras. In the reflex design, light travels through the lens, then to a mirror that alternates to send the image to either the viewfinder or the image sensor. The traditional alternative would be to have a viewfinder with its own lens, hence the term "single lens" for this design. By using only one lens, the viewfinder of a DSLR presents an image that will not differ substantially from what is captured by the camera's sensor. A DSLR differs from non-reflex single-lens digital cameras in that the viewfinder presents a direct optical view through the lens, rather than being captured by the camera's image sensor and displayed by a digital screen.

DSLRs largely replaced film-based SLRs during the 2000s, and despite the rising popularity of mirrorless system cameras in the early 2010s, DSLRs remain the most common type of interchangeable lens camera in use as of 2018.Like SLRs DSLRs typically use interchangeable lenses with a proprietary lens mount. A movable mechanical mirror system ( is switched down (exact 45-degree angle) to direct light from the lens over a matte focusing screen via a condenser lens  and a pentaprism/pentamirror  to an optical viewfinder eyepiece . Most of the entry-level DSLRsuse a pentamirror instead of the traditional pentaprism.

Focusing can be manual, by twisting the focus on the lens; or automatic, activated by pressing half-way on the shutter release or a dedicated AF button. To take an image, the mirror swings upwards in the direction of the arrow, the focal-plane shutter  opens, and the image is projected and captured on the image sensor , after which actions, the shutter closes, the mirror returns to the 45-degree angle, and the built in drive mechanism re-tensions the shutter for the next exposure.

Compared with the newer concept of mirrorless interchangeable-lens cameras, this mirror/prism system is the characteristic difference providing direct, accurate optical preview with separate autofocus and exposure metering sensors. Essential parts of all digital cameras are some electronics like amplifier, analog to digital converter, image processor and other (micro-)processors for processing the digital image, performing data storage and/or driving an electronic display.

Design of DSLR camera

Like SLRs DSLRs typically use interchangeable lenses with a proprietary lens mount. A movable mechanical mirror system  is switched down (exact 45-degree angle) to direct light from the lens over a matte focusing screen  via a condenser lens  and a pentaprism/pentamirror  to an optical viewfinder eyepiece  Most of the entry-level DSLRsuse a pentamirror instead of the traditional pentaprism.

Focusing can be manual, by twisting the focus on the lens; or automatic, activated by pressing half-way on the shutter release or a dedicated AF button. To take an image, the mirror swings upwards in the direction of the arrow, the focal-plane shutter opens, and the image is projected and captured on the image sensor , after which actions, the shutter closes, the mirror returns to the 45-degree angle, and the built in drive mechanism re-tensions the shutter for the next exposure.

Compared with the newer concept of mirrorless interchangeable-lens cameras, this mirror/prism system is the characteristic difference providing direct, accurate optical preview with separate autofocus and exposure metering sensors. Essential parts of all digital cameras are some electronics like amplifier, analog to digital converter, image processor and other (micro-)processors for processing the digital image, performing data storage and/or driving an electronic display.

Phase-detection autofocus

DSLRs typically use autofocus based on phase detection. This method allows the optimal lens position to be calculated, rather than "found", as would be the case with autofocus based on contrast maximisation. Phase-detection autofocus is typically faster than other passive techniques. As the phase sensor requires the same light going to the image sensor, it was previously only possible with an SLR design. However, with the introduction of focal-plane phase detect autofocusing in mirrorless interchangeable lens cameras by Sony, Fuji, Olympus and Panasonic, cameras can now employ both phase detect and contrast detect AF points.

Features commonly seen in DSLR designs

Cutaway of an Olympus E-30 DSLR (key: see above)

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Mode dial

Digital SLR cameras, along with most other digital cameras, generally have a mode dial to access standard camera settings or automatic scene-mode settings. Sometimes called a "PASM" dial, they typically provide modes such as program, aperture-priority, shutter-priority, and full manual modes. Scene modes vary from camera to camera, and these modes are inherently less customizable. They often include landscape, portrait, action, macro, night, and silhouette, among others. However, these different settings and shooting styles that "scene" mode provides can be achieved by calibrating certain settings on the camera. Professional DSLRs seldom contain automatic scene modes as professionals often do not require these and professionals know how to achieve the looks they want.

Dust reduction systems

A method to prevent dust entering the chamber, by using a "dust cover" filter right behind the lens mount, was used by Sigma in its first DSLR, the Sigma SD9, in 2002

Olympus used a built-in sensor cleaning mechanism in its first DSLR that had a sensor exposed to air, the Olympus E-1, in 2003 (all previous models each had a non-interchangeable lens, preventing direct exposure of the sensor to outside environmental conditions).

Several Canon DSLR cameras rely on dust reduction systems based on vibrating the sensor at ultrasonic frequencies to remove dust from the sensor.

Interchangeable lenses

Canon EF-S 18-135mm APS-C Zoom lens

The ability to exchange lenses, to select the best lens for the current photographic need, and to allow the attachment of specialised lenses, is one of the key factors in the popularity of DSLR cameras, although this feature is not unique to the DSLR design and mirrorless interchangeable lens cameras are becoming increasingly popular. Interchangeable lenses for SLRs and DSLRs (also known as "Glass") are built to operate correctly with a specific lens mount that is generally unique to each brand. A photographer will often use lenses made by the same manufacturer as the camera body (for example, Canon EF lenses on a Canon body) although there are also many independent lens manufacturers, such as Sigma, Tamron, Tokina, and Vivitar that make lenses for a variety of different lens mounts. There are also lens adapters that allow a lens for one lens mount to be used on a camera body with a different lens mount but with often reduced functionality.

Many lenses are mountable, "diaphragm-and-meter-compatible", on modern DSLRs and on older film SLRs that use the same lens mount. However, when lenses designed for 35 mm film or equivalently sized digital image sensors are used on DSLRs with smaller sized sensors, the image is effectively cropped and the lens appears to have a longer focal length than its stated focal length. Most DSLR manufacturers have introduced lines of lenses with image circles optimised for the smaller sensors and focal lengths equivalent to those generally offered for existing 35 mm mount DSLRs, mostly in the wide angle range. These lenses tend not to be completely compatible with full frame sensors or 35 mm film because of the smaller imaging circle and, with some Canon EF-S lenses, interfere with the reflex mirrors on full-frame bodies.

HD video capture

Since 2008, manufacturers have offered DSLRs which offer a movie mode capable of recording high definition motion video. A DSLR with this feature is often known as an HDSLR or DSLR video shooter.^[3] The first DSLR introduced with an HD movie mode, the Nikon D90, captures video at 720p24 (1280x720 resolution at 24 frame/s). Other early HDSLRs capture video using a nonstandard video resolution or frame rate. For example, the Pentax K-7 uses a nonstandard resolution of 1536×1024, which matches the imager's 3:2 aspect ratio. The Canon EOS 500D (Rebel T1i) uses a nonstandard frame rate of 20 frame/s at 1080p, along with a more conventional 720p30 format.

In general, HDSLRs use the full imager area to capture HD video, though not all pixels (causing video artifacts to some degree). Compared with the much smaller image sensors found in the typical camcorder, the HDSLR's much larger sensor yields distinctly different image characteristics. HDSLRs can achieve much shallower depth of field and superior low-light performance. However, the low ratio of active pixels (to total pixels) is more susceptible to aliasing artifacts (such as moire patterns) in scenes with particular textures, and CMOS rolling shutter tends to be more severe. Furthermore, due to the DSLR's optical construction, HDSLRs typically lack one or more video functions found on standard dedicated camcorders, such as autofocus while shooting, powered zoom, and an electronic viewfinder/preview. These and other handling limitations prevent the HDSLR from being operated as a simple point-and-shoot camcorder, instead demanding some level of planning and skill for location shooting.

Video functionality has continued to improve since the introduction of the HDSLR, including higher video resolution (such as 1080p24) and video bitrate, improved automatic control (autofocus) and manual exposure control, and support for formats compatible with high-definition television broadcast, Blu-ray disc mastering or Digital Cinema Initiatives (DCI). The Canon EOS 5D Mark II (with the release of firmware version 2.0.3/2.0.4.) and Panasonic Lumix GH1 were the first HDSLRs to offer broadcast compliant 1080p24 video, and since then the list of models with comparable functionality has grown considerably.

The rapid maturation of HDSLR cameras has sparked a revolution in digital filmmaking, and the "Shot On DSLR" badge is a quickly growing phrase among independent filmmakers. Canon's North American TV advertisements featuring the Rebel T1i have been shot using the T1i itself. An increased number of films, documentaries, television shows, and other productions are utilizing the quickly improving features. One such project was Canon's "Story Beyond the Still" contest that asked filmmakers to collectively shoot a short film in 8 chapters, with each chapter being shot over a short period of time and a winner was determined for each chapter. After 7 chapters the winners collaborated to shoot the final chapter of the story. Due to the affordability and convenient size of HDSLRs compared with professional movie cameras, The Avengers used five Canon EOS 5D Mark II and two Canon 7Dto shoot the scenes from various vantage angles throughout the set and reduced the number of reshoots of complex action scenes.

Sony ECM-CG50 shotgun-type microphone for DSLR video capture

Manufacturers have sold optional accessories to optimize a DSLR camera as a video camera, such as a shotgun-type microphone, and an External EVF with 1.2 million pixels.

Live preview[edit]

Nikon D90 in Liveview mode also usable for 720p HD video

Early DSLRs lacked the ability to show the optical viewfinder's image on the LCD display – a feature known as live preview. Live preview is useful in situations where the camera's eye-level viewfinder cannot be used, such as underwater photography where the camera is enclosed in a plastic waterproof case.

In 2000, Olympus introduced the Olympus E-10, the first DSLR with live preview – albeit with an atypical fixed lens design. In late 2008, some DSLRs from Canon, Nikon, Olympus, Panasonic, Leica, Pentax, Samsung and Sony all provided continuous live preview as an option. Additionally, the Fujifilm FinePix S5 Pro offers 30 seconds of live preview.

On almost all DSLRs that offer live preview via the primary sensor, the phase detection autofocus system does not work in the live preview mode, and the DSLR switches to a slower contrast system commonly found in point & shoot cameras. While even phase detection autofocus requires contrast in the scene, strict contrast detection autofocus is limited in its ability to find focus quickly, though it is somewhat more accurate.

In 2012, Canon introduced hybrid autofocus technology to the DSLR in the EOS 650D/Rebel T4i, and introduced a more sophisticated version, which it calls "Dual Pixel CMOS AF", with the EOS 70D. The technology allows certain pixels to act as both contrast-detection and phase-detection pixels, thereby greatly improving autofocus speed in live view (although it remains slower than pure phase detection). While several mirrorless cameras, plus Sony's fixed-mirror SLTs, have similar hybrid AF systems, Canon is the only manufacturer that offers such a technology in DSLRs.

A new feature via a separate software package introduced from Breeze Systems in October 2007, features live view from a distance. The software package is named "DSLR Remote Pro v1.5" and enables support for the Canon EOS 40D and 1D Mark III

Larger sensor sizes and better image quality

Drawing showing the relative sizes of sensors used in current digital cameras.

Image sensors used in DSLRs come in a range of sizes. The very largest are the ones used in "medium format" cameras, typically via a "digital back" which can be used as an alternative to a film back. Because of the manufacturing costs of these large sensors the price of these cameras is typically over $6,500 as of May 2014.

"Full-frame" is the same size as 35 mm film (135 film, image format 24×36 mm); these sensors are used in DSLRs such as the Canon EOS-1D X Mark II, 5DS/5DSR, 5D Mark IV and 6D Mark II, and the Nikon D5, D850, D750, D610 and Df. Most modern DSLRs use a smaller sensor that is APS-C sized, which is approximately 22×15 mm, slightly smaller than the size of an APS-C film frame, or about 40% of the area of a full-frame sensor. Other sensor sizes found in DSLRs include the Four Thirds System sensor at 26% of full frame, APS-H sensors (used, for example, in the Canon EOS-1D Mark III) at around 61% of full frame, and the original Foveon X3 sensor at 33% of full frame (although Foveon sensors since 2013 have been APS-C sized). Leica offers an "S-System" DSLR with a 30×45 mm array containing 37 million pixels. This sensor is 56% larger than a full-frame sensor.

The resolution of DSLR sensors is typically measured in megapixels. More expensive cameras and cameras with larger sensors tend to have higher megapixel ratings. A larger megapixel rating does not mean higher quality. Low light sensitivity is a good example of this. When comparing two sensors of the same size, for example two APS-C sensors one 12.1 MP and one 18 MP, the one with the lower megapixel rating will usually perform better in low light. This is because the size of the individual pixels is larger, and more light is landing on each pixel, compared with the sensor with more megapixels. This is not always the case, because newer cameras that have higher megapixels also have better noise reduction software, and higher ISO settings to make up for the loss of light per pixel due to higher pixel density.

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Depth-of-field control

The lenses typically used on DSLRs have a wider range of apertures available to them, ranging from as large as f/0.9 to about f/32. Lenses for smaller sensor cameras rarely have true available aperture sizes much larger than f/2.8 or much smaller than f/5.6.

To help extend the exposure range, some smaller sensor cameras will also incorporate an ND filter pack into the aperture mechanism.

The apertures that smaller sensor cameras have available give much more depth of field than equivalent angles of view on a DSLR. For example, a 6 mm lens on a 2/3″ sensor digicam has a field of view similar to a 24 mm lens on a 35 mm camera. At an aperture of f/2.8 the smaller sensor camera (assuming a crop factor of 4) has a similar depth of field to that 35 mm camera set to f/11.

Wider angle of view

An APS-C format SLR (left) and a full-frame DSLR (right) show the difference in the size of the image sensors.

The angle of view of a lens depends upon its focal length and the camera's image sensor size; a sensor smaller than 35 mm film format (36×24 mm frame) gives a narrower angle of view for a lens of a given focal length than a camera equipped with a full-frame (35 mm) sensor. As of 2017, only a few current DSLRs have full-frame sensors, including the Canon EOS-1D X Mark II, EOS 5D Mark IV, EOS 5DS/5DS R, and EOS 6D Mark II; Nikon's D5, D610, D750, D850, and Df; and the Pentax K-1. The scarcity of full-frame DSLRs is partly a result of the cost of such large sensors. Medium format size sensors, such as those used in the Mamiya ZD among others, are even larger than full-frame (35 mm) sensors, and capable of even greater resolution, and are correspondingly more expensive.

The impact of sensor size on field of view is referred to as the "crop factor" or "focal length multiplier", which is a factor by which a lens focal length can be multiplied to give the full-frame-equivalent focal length for a lens. Typical APS-C sensors have crop factors of 1.5 to 1.7, so a lens with a focal length of 50 mm will give a field of view equal to that of a 75 mm to 85 mm lens on a 35 mm camera. The smaller sensors of Four Thirds System cameras have a crop factor of 2.0.

While the crop factor of APS-C cameras effectively narrows the angle of view of long-focus (telephoto) lenses, making it easier to take close-up images of distant objects, wide-angle lenses suffer a reduction in their angle of view by the same factor.

DSLRs with "crop" sensor size have slightly more depth-of-field than cameras with 35 mm sized sensors for a given angle of view. The amount of added depth of field for a given focal length can be roughly calculated by multiplying the depth of field by the crop factor. Shallower depth of field is often preferred by professionals for portrait work and to isolate a subject from its background.

Unusual features

On July 13, 2007, FujiFilm announced the FinePix IS Pro, which uses Nikon F-mount lenses. This camera, in addition to having live preview, has the ability to record in the infrared and ultraviolet spectra of light.

In August 2010 Sony released series of DSLRs allowing 3D photography. It was accomplished by sweeping the camera horizontally or vertically in Sweep Panorama 3D mode. The picture could be saved as ultra-wide panoramic image or as 16:9 3D photography to be viewed on BRAVIA 3D television set.

DSLRs compared with other digital cameras

The reflex design scheme is the primary difference between a DSLR and other digital cameras. In the reflex design scheme, the image captured on the camera's sensor is also the image that is seen through the view finder. Light travels through a single lens and a mirror is used to reflect a portion of that light through the view finder – hence the name Single Lens Reflex. While there are variations among point-and-shoot cameras, the typical design exposes the sensor constantly to the light projected by the lens, allowing the camera's screen to be used as an electronic viewfinder. However, LCDs can be difficult to see in very bright sunlight.

Compared with some low cost cameras that provide an optical viewfinder that uses a small auxiliary lens, the DSLR design has the advantage of being parallax-free: it never provides an off-axis view. A disadvantage of the DSLR optical viewfinder system is that when it is used, it prevents using the LCD for viewing and composing the picture. Some people prefer to compose pictures on the display – for them this has become the de facto way to use a camera. Depending on the viewing position of the reflex mirror (down or up), the light from the scene can only reach either the viewfinder or the sensor. Therefore, many early DSLRs did not provide "live preview" (i.e., focusing, framing, and depth-of-field preview using the display), a facility that is always available on digicams. Today most DSLRs can alternate between live view and viewing through an optical viewfinder.

Optical view image and digitally created image

The larger, advanced digital cameras offer a non-optical electronic through-the-lens (TTL) view, via an eye-level electronic viewfinder (EVF) in addition to the rear LCD. The difference in view compared with a DSLR is that the EVF shows a digitally created image, whereas the viewfinder in a DSLR shows an actual optical image via the reflex viewing system. An EVF image has lag time (that is, it reacts with a delay to view changes) and has a lower resolution than an optical viewfinder but achieves parallax-free viewing using less bulk and mechanical complexity than a DSLR with its reflex viewing system. Optical viewfinders tend to be more comfortable and efficient, especially for action photography and in low-light conditions. Compared with digital cameras with LCD electronic viewfinders, there is no time lag in the image: it is always correct as it is being "updated" at the speed of light. This is important for action or sports photography, or any other situation where the subject or the camera is moving quickly. Furthermore, the "resolution" of the viewed image is much better than that provided by an LCD or an electronic viewfinder, which can be important if manual focusing is desired for precise focusing, as would be the case in macro photography and "micro-photography" (with a microscope). An optical viewfinder may also cause less eye-strain. However, electronic viewfinders may provide a brighter display in low light situations, as the picture can be electronically amplified.

Performance differences

DSLR cameras often have image sensors of much larger size and often higher quality, offering lower noise,^[40] which is useful in low light. Although mirrorless digital cameras with APS-C and full frame sensors exist, most full frame and medium format sized image sensors are still seen in DSLR designs.

For a long time, DSLRs offered faster and more responsive performance, with less shutter lag, faster autofocus systems, and higher frame rates. Around 2016-17, specific mirrorless camera models started offering competitive or superior specifications in these aspects. The downside of these cameras being that they do not have an optical viewfinder, making it difficult to focus on moving subjects or in situations where a fast burst mode would be beneficial. Other digital cameras were once significantly slower in image capture (time measured from pressing the shutter release to the writing of the digital image to the storage medium) than DSLR cameras, but this situation is changing with the introduction of faster capture memory cards and faster in-camera processing chips. Still, compact digital cameras are not suited for action, wildlife, sports and other photography requiring a high burst rate (frames per second).

Simple point-and-shoot cameras rely almost exclusively on their built-in automation and machine intelligence for capturing images under a variety of situations and offer no manual control over their functions, a trait which makes them unsuitable for use by professionals, enthusiasts and proficient consumers (aka "prosumers"). Bridge cameras provide some degree of manual control over the camera's shooting modes, and some even have hotshoes and the option to attach lens accessories such as filters and secondary converters. DSLRs typically provide the photographer with full control over all the important parameters of photography and have the option to attach additional accessories^[41] including hot shoe-mounted flash units, battery grips for additional power and hand positions, external light meters, and remote controls. DSLRs typically also have fully automatic shooting modes.

DSLRs have a larger focal length for the same field of view, which allows creative use of depth of field effects.However, small digital cameras can focus better on closer objects than typical DSLR lenses.

Sensor size

The sensors used in current DSLRs ("Full-frame" which is the same size as 35 mm film (135 film, image format 24×36 mm), APS-C sized, which is approximately 22×15 mm, and Four Thirds System) are typically much larger than the sensors found in other types of digital cameras. Entry-level compact cameras typically use sensors known as 1/2.5″, which is 3% the size of a full frame sensor. There are bridge cameras (also known as premium compact cameras or enthusiast point-and-shoot cameras) that offer sensors larger than 1/2.5″ but most still fall short of the larger sizes widely found on DSLR. Examples include the Sigma DP1, which uses a Foveon X3 sensor; the Leica X1; the Canon PowerShot G1 X, which uses a 1.5″ (18.7×14 mm) sensor that is slightly larger than the Four Thirds standard and is 30% of a full-frame sensor; the Nikon Coolpix A, which uses an APS-C sensor of the same size as those found in the company's DX-format DSLRs; and two models from Sony, the RX100 with a 1″-type (13.2×8.8 mm) sensor with about half the area of Four Thirds and the full-frame Sony RX1. These premium compacts are often comparable to entry-level DSLRs in price, with the smaller size and weight being a tradeoff for the smaller sensor.

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Fixed or interchangeable lenses

Unlike DSLRs, most digital cameras lack the option to change the lens. Instead, most compact digital cameras are manufactured with a zoom lens that covers the most commonly used fields of view. Having fixed lenses, they are limited to the focal lengths they are manufactured with, except for what is available from attachments. Manufacturers have attempted (with increasing success) to overcome this disadvantage by offering extreme ranges of focal length on models known as superzooms, some of which offer far longer focal lengths than readily available DSLR lenses.

There are now available perspective-correcting (PC) lenses for DSLR cameras, providing some of the attributes of view cameras. Nikon introduced the first PC lens, fully manual, in 1961. Recently, however, some manufacturers have introduced advanced lenses that both shift and tilt and are operated with automatic aperture control.

However, since the introduction of the Micro Four Thirds system by Olympus and Panasonic in late 2008, mirrorless interchangeable lens cameras are now widely available so the option to change lenses is no longer unique to DSLRs. Cameras for the micro four thirds system are designed with the option of a replaceable lens and accept lenses that conform to this proprietary specification. Cameras for this system have the same sensor size as the Four Thirds System but do not have the mirror and pentaprism, so as to reduce the distance between the lens and sensor.

Panasonic released the first Micro Four Thirds camera, the Lumix DMC-G1. Several manufacturers have announced lenses for the new Micro Four Thirds mount, while older Four Thirds lenses can be mounted with an adapter (a mechanical spacer with front and rear electrical connectors and its own internal firmware). A similar mirror-less interchangeable lens camera, but with an APS-C-sized sensor, was announced in January 2010: the Samsung NX10. On 21 September 2011, Nikon announced with the Nikon 1 a series of high-speedMILCs. A handful of rangefinder cameras also support interchangeable lenses. Six digital rangefinders exist: the Epson R-D1 (APS-C-sized sensor), the Leica M8 (APS-H-sized sensor), both smaller than 35 mm film rangefinder cameras, and the Leica M9, M9-P, M Monochrom and M (all full-frame cameras, with the Monochrom shooting exclusively in black-and-white).

In common with other interchangeable lens designs, DSLRs must contend with potential contamination of the sensor by dust particles when the lens is changed (though recent dust reduction systems alleviate this). Digital cameras with fixed lenses are not usually subject to dust from outside the camera settling on the sensor.

DSLRs generally have greater cost, size, and weight. They also have louder operation, due to the SLR mirror mechanism. Sony's fixed mirror design manages to avoid this problem. However, that design has the disadvantage that some of the light received from the lens is diverted by the mirror and thus the image sensor receives about 30% less light compared with other DSLR designs.

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