Digital Single-Lens Reflex

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 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 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 presents an image that will not perceptibly differ from what is captured by the camera’s sensor.

Cutaway of an Olympus E-30 DSLR

Canon EF-S 18-135mm APS-C Zoom lens

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

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

Sony Alpha 99, full-frame digital SLT camera


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

Pentax is a brand name used primarily by Ricoh Imaging Company​

Canon EOS 60D APS-C digital SLR with lens removed​.


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

Storage Unit

Kodak DCS 100, based on a Nikon F3 body with Digital Storage Unit, released in May 1991.