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. Many lenses are mountable, “diaphragm-and-meter-compatible”, on modern DSLRs and on older film SLRs that use the same lens mount. 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. 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. 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. 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.
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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. To take an image, the mirror swings upwards in the direction of the arrow, the focal-plane shutter (3) opens, and the image is projected and captured on the image sensor (4), 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.Ĭompared 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.
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Most of the entry-level DSLRs use a pentamirror instead of the traditional pentaprism.įocusing 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. A movable mechanical mirror system (2) is switched down (exact 45-degree angle) to direct light from the lens over a matte focusing screen (5) via a condenser lens (6) and a pentaprism/pentamirror (7) to an optical viewfindereyepiece (8). Like SLRs, DSLRs typically use interchangeable lenses (1) with a proprietary lens mount. 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.ĭSLRs 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. 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.
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The traditional alternative would be to have a viewfinder with its own lens, hence the term “single lens” for this design. 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 reflex design scheme is the primary difference between a DSLR and other digital cameras. A digital single-lens reflex camera ( 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.