Digital single-lens reflex camera

A digital single-lens reflex camera (also called a digital SLR or DSLR) is a digital camera combining the optics and the mechanisms of a single-lens reflex camera with a digital imaging sensor, as opposed to photographic films. 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 view finder  or the image sensor. The 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 view finder of a DSLR presents an image that will not perceptibly differ from what is captured by the camera's sensor.

DSLRs largely replaced film-based SLRs during the 2000s, and despite the rising popularity of mirrorless system cameras in the early 2010s, DSLRs remained the most common type of interchangable lens camera in use as of 2014.

Features:

• 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 as minimum Program, Aperture-priority, Shutter-priority, and full Manual modes. Scene modes vary and are inherently less customizable.

• DUST REDUCTION SYSTEM:

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.

• INTERCHANGEABLE 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.

• 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. The first DSLR introduced with an HD movie mode, the NIKON D90, captures video at 720P24 (1280x720 resolution at 24 frames). 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.

• Live preview:

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 under water photography where the camera is enclosed in a plastic waterproof case. 

• LARGER SENSOR SIZE:

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.

• WIDER ANGLE OF VIEW:

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.