In digital camera terminology, the term DSLR stands for digital single-lens reflex camera. A DSLR camera operates differently than a standard point-and-shoot digital camera. Some defining characteristics are full manual control of camera functions and the ability to attach with and utilize separate lenses. By contrast, point-and-shoot digital cameras usually have a fixed lens, limiting their versatility. Nearly all professionals in the photography industry use DSLRs with high-end functions, as film camera use has faded.
Digital SLR cameras use a mirror within the camera behind the lens mount but before the image sensor. This mirror, in conjunction with a prism, means the photographer sees through the viewfinder the actual image that will be taken. By contrast, digital point-and-shoot cameras do not give the photographer the exact view the lens's sensor is seeing, as they use a separate lens for the viewfinder. When serious photographers snap an image, especially with lenses with long focal lengths, it is imperative to see an accurate representation of the image. This, along with the ability to switch lenses on the fly, is the chief benefit of a DSLR.
All but the most high-end digital point-and-shoot cameras have limited manual control over camera functions. DSLR cameras offer the photographer more options and the ability to switch camera settings on the fly using dedicated physical hardware buttons and dials. Shutter speed controls how long the camera's shutter stays open. Higher shutter speeds allow easier focus and the ability to freeze quick action but let in less light. Aperture controls the degree by which the shutter opens. ISO rating emulates different film speeds used by film cameras. Professional DSLR cameras can shoot at significantly higher ISO ratings than entry-level models, giving the photographer greater options for shooting in different light conditions. There are many more esoteric settings of which DSLRs offer full manual control.
Lenses, Focus and Sensors
Removable lenses give the DSLR photographer countless options for different photographs in different situations. Most point-and-shoot cameras come with a single zoom lens capable of different focal lengths but within a relatively limited range. Extreme close-up, or macro, lenses and those with long focal lengths for capturing distant images are among the DSLR photographer's tools. While full manual controls are useful, professional cameras use automatic shooting modes with autofocus built either into the lens or the camera body. Imaging sensor size is also key to camera performance. Megapixel ratings can be deceptive, as images taken at the same megapixel size but with a larger sensor size generally turn out in higher quality. Low-to-midrange DSLRs usually use a sensor sized around 23-by-15 mm. By contrast, professional digital single-lens reflex cameras often use an image sensor approximately the size of a piece of 35 mm film.
Entry-level Versus Professional DSLR Cameras
Digital single-lens reflex cameras span a wide range of price points, image quality and features. Top-selling entry-to-midlevel DSLRs court the casual and enthusiast markets, while more expensive models cater to professionals. Professional cameras are larger and bulkier with feature sets likely beyond the needs of most interested in photography. A third category, which tech review site CNET calls "prosumer," offers high-end image quality combined with the compact size and ease of use of inexpensive DSLRs.