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.]] A digital single-lens reflex camera ('''digital SLR''' or '''DSLR''') is a Digital Camera that operates on the same optical and mechanical principles as a modern electronic autofocus 35mm Film Single-lens Reflex Camera . The key difference is that the film is replaced with a CCD or CMOS sensor plus accompanying electronics, thus creating images digitally in-camera, without the need to first chemically develop the image captured. A major attraction of digital SLR cameras as compared to non-SLR digitals has been to allow photographers to convert from 35mm film cameras using the lenses and equipment that they are familiar with. For this reason, camera manufacturers design digital SLRs to be as similar as possible to their film counterparts. SLR DESIGN The single-lens reflex (SLR) camera uses a mirror to show the image that will be captured on film in a Viewfinder . At the time of taking the photograph, the mirror is moved out of the light path. The principal advantage of the SLR film camera over non-SLR film cameras is the ability to see the image exactly as it would appear on film, whatever the lens used, and without Parallax errors due to a viewfinder offset from the lens. While non-SLR cameras can have interchangeable optics, a viewfinder must be provided for each one. Close-up and Macro Photography are particularly affected by Parallax . Most of these advantages transfer directly to any digital camera with electronic viewfinder screen, even if not of SLR construction: the viewfinder always shows the image on the sensor, exactly as it will be captured in the photograph. Actually, both film SLRs and digital screens tend to show slightly more of the edges of the image than will be included. SLR viewing has the advantages over non-SLR digital screens of zero lag time and absence of heavy power drain, and is usually more robust and reliable. In the digital era Zoom Lens design is sufficiently advanced to almost eliminate the market for non-SLR cameras with interchangeable lenses, so lens interchangability is, in practice, restricted to the digital SLR. A non-SLR camera can have a fixed lens which will zoom from medium wide-angle to medium telephoto, omitting only fish-eye and extreme telephoto. However, there are at least four advanced digital non-SLR camera with interchangeable lenses (see "Compacts" below). The imaging sensor in a DSLR is typically much larger than the one in a consumer-level, compact Digital Camera . A larger sensor allows better image quality, lower noise, shallower Depth Of Field and wider Field Of View . Many DSLR sensors are roughly APS-sized, i.e., approximately 22 mm x 15 mm, the size of an APS film frame, smaller than a frame of 135 Film . The angle of view of a lens depends upon its focal length and the image size; a sensor smaller than 35mm film means that a lens of given focal length will have a narrower angle of view than it would on 35mm film. If the sensor is the same size as the equivalent frame of film (36 mm x 24 mm), the camera is said to have a 35mm, or ''full-frame sensor''. As of 2006 only a few DSLRs have full-frame sensors (the Canon EOS-1Ds Mark II and the Canon EOS 5D ). Medium-format size sensors, as used on the Mamiya ZD and other cameras, are even larger than 35mm or full-frame sensors, and capable of even greater image quality. 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-eqivalent focal length for a lens. Roughly APS-sized sensors have a crop factor of 1.5 or 1.6, so a lens with a focal length of 50mm will give a FOV equal to that of a 75mm or 80mm lens on a full-frame camera. This crop makes achieving long telephoto images on an APS-sensor camera much easier than on a full-frame camera; though wide-angle views suffer by the same amount. Shallow depth-of-field images also tend to be more difficult to achieve with smaller sensors. Depending on the position of the reflex mirror, the light from the scene can only reach either the and the Panasonic Lumix DMC-L1 (available sometime in 2006) — both of which are Four Thirds System cameras. Camera manufacturers currently expect that professionals and advanced amateurs will continue to prefer DSLRs over other forms of digital cameras. However, if electronic viewfinders with near-zero lag time, increased reliability, and very low power consumption are introduced, non-SLR cameras may become a viable choice for a large number of people who now need SLRs. Many Medium Format roll-film SLRs can accept a Digital Camera Back to turn the camera into a DSLR with very high image resolution and quality (typically 22 megapixel as of 2005 ). However, the combination is very expensive and bulky, and more suited to the studio than an outdoor environment. HISTORY At Fotokina in 1986, Nikon revealed a prototype analog electronic still SLR camera, the Nikon SVC, a precursor to the digital SLR The prototype design lead to the Nikon N8008 two years later which is capable of 0.3 megapixel [http://apphotnum.free.fr/N2BE2.html . In 1991, Kodak released the first comercially available digital SLR, the Kodak DCS-100. It consisted of a modified Nikon F3 SLR body, modified drive unit, and an external storage unit connected via cable. The camera was capable of producing 1.3 megapixel (1280x1024) and cost approximately $30,000 US. This was followed by the DCS-200 with integrated storage {Link without Title} . Over the next decade, digital SLRs have been released by various companies such as Canon , Nikon , Kodak , Pentax , Olympus , Konica Minolta , Fujifilm , and Sigma with higher resolution and lower prices. In 2003 , Canon introduced a 6.3 Megapixel Digital Rebel SLR camera (known in the UK as the EOS 300D) at an MSRP of under $1000. Its popularity, especially among newspaper and amateur photographers, encouraged other manufacturers to produce affordable digital SLR cameras, significantly lowering entry costs and allowing more casual photographers an opportunity to experience the digital SLR photography. Canon introduced the next generation 8 megapixel EOS350D (Digital Rebel XT) in 2005. Kodak made a major impact on DSLR history by releasing two distinct 14-MP DSLR cameras for Nikon and Canon lens mounts. These cameras were extremely expensive, and Kodak has since discontinued them. Konica Minolta briefly produced two DSLR models, the 5D and 7D, but has sold their digital camera business to Sony and ceased all DSLR production. At one time, Kyocera also manufactured DSLRs and marketed them under the Contax name, but in 2005 withdrew from the DSLR camera field. Sigma produced the SD9 and SD10 DSLR cameras with the Foveon X3 Sensor , but those cameras are no longer in production; a successor has been promised but not yet announced. Canon , Nikon , Pentax , Olympus , and Fujifilm currently have DSLR models in production. PRESENT DAY Canon and Nikon currently have the largest range of amateur and professional DSLR cameras. Canon's line includes the 350D , 30D , 5D and the 1Ds Mk. II . Nikon also has a broad line of DSLRs which includes the D50 , D70s , D200 , D2Hs and D2X . Nikon has also concentrated on improving the weather resistance and sealing of its DSLR cameras, in order to improve DSLR reliability in extreme conditions. Fujifilm sells a Nikon-lens compatible DSLR, and Olympus has introduced two DSLR models of its own design. Sigma produces an innovative DSLR with the multi-layered Foveon X3 Sensor to deliver excellent color and detail for its size and imaging limits, while Pentax also has digital SLRs that use their lenses and accessories. Mamiya has produced a medium-format SLR, the Mamiya ZD that currently produces the highest quality digital images, its larger sensor able to capture much more detail than the 35mm full-frame and smaller sensors found on the Canon, Nikon, Olympus, Pentax, and Sigma models. DIGITAL SLR VERSUS SLR-LIKE AND COMPACT CAMERAS Non-SLR digital cameras are of two types: SLR-like "prosumer" cameras with permanently fixed zoom lenses, and digital compacts cameras. SLR-like cameras The SLR-like "prosumer" cameras (e.g. some Nikon Coolpix models, the Sony DSC H and R series, the Panasonic FZ series, the Canon PowerShot S and Pro models, and several Fujifilm FinePix models) offer TTL viewing through the focusing lens, projected onto its viewfinder as well as a LCD screen, through an EVF (electronic viewfinder). The difference compared to a DSLR is that the viefinder shows a digitally created copy of the TTL image whereas the viewfinder in a DSLR shows the real optical TTL image via its mirror. An EVF image reacts slower to view changes and has a lower resolution than an optical viewfinder, but its advantages are parallax-free views and far lesser bulk and mechanical complexity than a DSLR with its reflex viewing system. The disadvantage of a prosumer digital camera is, of course, its fixed lens, but on the other hand modern SLR-like prosumer cameras have very capable zoom lenses, some ranging (in 35 mm equivalents) from 28 to 300 mm, which makes the inability to change lenses less of an issue for the users. Also, the fixed lens minimises the risk of dust on the sensor, something that is almost unavoidable when you change lenses on a DSLRs. Several of the high-end prosumer cameras have a moveable LCD screen, which can be used instead of the regular viewfinder in difficult angles, enabling the photographer to look through the lens even when standing above or below the camera. The LCD screen also enables the photographer to look at the stored pictures in a convenient way. Compacts The compact digital cameras can usually be operated at arm's length using only the LCD display screen at the rear of the camera, and most models also have simple optical viewfinders like traditional compact film cameras. Like the SLR-like prosumer cameras, nearly all compacts have no ability to accept interchangeable lenses, with the exception of the professional Leica Digilux models, Panasonic DMC-L1 and Epson R-D1. Most compacts are therefore provided with a zoom lens that covers the most commonly used focal lengths. Compacts may be altered through the use of supplementary add-on lens converters to provide an added telephoto or wide angle field of view, though the image quality is usually affected to a significant degree. Most compacts are significantly slower in shutter speed capture (time from image capture to sensor and storage) than DSLR cameras, a disadvantage for action, wildlife, and sports photography. Their zoom lenses can frequently have a much slower (smaller) effective wide-open aperture (f-stop) than DSLR or prosumer cameras, especially at the telephoto end, which further limits their utility in situations involving low light levels and moving subjects. SEE ALSO |
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