Although digital photography has a lot of distinct features when compared to film photography, the parent-child relationship between the two is obvious. Digital photography takes its roots from film photography and nothing illustrates this concept better than SLR, or Single Lens Reflex technology.

The single lens reflex concept first appeared in film cameras that used a movable mirror between the lens and the film, which projected the image seen through the lens to the focusing screen. The pentamirror (a five sided form mirror) used by most film SLR cameras moves in a semi-circular fashion and allows the projection of the picture on the film. Digital SLR photography uses the same principles used by its film counterpart, but takes them to a whole new level. The same optical and mechanical concepts apply, but sensors are used to store the data instead and evidently, the pictures are stored electronically instead of on a latent film.

There are 4 basic advantages of using digital SLR photography, as follows:

 Fast phase detection auto focus – most cameras (regardless if they are film or digital) use an auto focus system but only digital ones use fast phase detection systems. These are highly efficient and are made available through the insertion of a special sensor in the optical path which regulates the focus point and view distance required. Since taking a picture is oftentimes a spontaneous act, rather than one where you have time to prepare every detail from lighting to focus, this fast autofocus system will prove invaluable.
 Interchangeable lenses – since each time you take a photo the external parameters might vary, the use of different lenses is often necessary. Digital SLR cameras offer an easy way to select he best lens for the job or to attach additional lenses with specialized abilities.
 Sensor quality – the sensorial quality of a SLR camera is usually a lot higher than for normal digital cameras. This allows for several benefits, including lower picture noise, grain reduction, adjusted depth of field, higher sensitivity and an overall better image quality.
 Parallax free optical viewfinder – this is actually one of the main advantages that SLR cameras have over other digital cameras and it is oftentimes considered a “trademark” of DSLR. Having a parallax free optical viewfinder, the camera will basically capture the picture “as you see it” instead of altering the parameters when the actual image is captured. A small setback would be that most on-camera LCD’s are small enough to hide some important details and they also alter the image themselves, so a good synchronization between the camera lens and the camera LCD is important if you want to get “exactly” what you’re aiming at.