Digital single-lens reflex camera

Digital single-lens reflex cameras (also called digital SLR or DSLR) are digital camerascombining 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 differ imperceptibly from what is captured by the camera's sensor.

Like SLRs DSLRs typically use interchangeable lenses (1) with a proprietary lens mount. A movable mechanical mirror system (2) is switched down (exact 45-degree angle) to direct light from the lensover a matte focusing screen (5) via a condenser lens (6) and apentaprism/pentamirror (7) to an optical viewfinder eyepiece (8). Most of the entry level DSLRs use a pentamirror instead of the traditional pentaprism. The pentamirror design is composed mostly of plastic and is lighter and cheaper to produce — however, the image in the viewfinder is usually darker.[1]

Focusing can be manual 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, thefocal-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.

Compared to the newer concept of mirrorless interchangeable-lens cameras this mirror/prism system is the characteristic difference providing direct, accurate optical preview with separate autofocusand 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.