SLR Camera Photographers

Single Lens Reflex cameras are the standard tool for serious photographers. The single-lens reflex camera uses an automatic moving mirror system that permits the photographer to see exactly what will be captured by the film or digital imaging system, as opposed to the non-SLR cameras where the view through the viewfinder could be significantly different from what was captured on film.

Prior to the development of SLR, all cameras with viewfinders had two optical light paths, one path was through the lens to the film, and another path positioned above TLR or twin-lens reflex or to the side, rangefinder. Because the viewfinder and the film lens cannot share the same optical path, the viewing lens is aimed to intersect with the film lens at a certain fixed point somewhere in front of the camera. This is not so problematic for pictures that are taken at a middle or longer distance but the phenomenon called ‘parallax’ causes framing errors in close-up shots. Moreover, focusing the lens of a non-reflex camera when it is opened to wider apertures (such as in low light or while using low-speed film) is not an easy task.

Most SLR cameras permit upright and laterally correct viewing through use of a pentaprism which is situated in the optical path between the reflex mirror and the viewfinder. Light is reflected by a movable mirror upwards right there into the pentaprism where it is reflected several times until it aligns with the viewfinder. When the shutter is being released, the mirror moves out of the light path and the light shines directly onto the film. Focus can either be adjusted manually by the photographer or automatically by an autofocus system. The viewfinder can include a matte focusing screen system located just above the mirror system to diffuse the light. This system permits accurate viewing, composing and focusing, and is especially useful with interchangeable lenses.

Up until the 1990s, SLR technology was the most advanced photographic preview system available. Although the recent development and refinement of digital imaging technology with an on-camera live LCD preview screen has some decent edge over SLR's such as nearly all inexpensive compact digital cameras now include an LCD preview screen allowing the photographer to see exactly what the CCD is capturing. However, SLR is still a popular and desired choice in high-end and professional cameras, because the pixel resolution, contrast ratio, refresh rate, and color gamut of an LCD preview screen cannot compete with the kind of clarity and shadow detail of a direct-viewed optical SLR viewfinder.

As compared to most of the fixed-lens compact cameras, the most commonly used and inexpensive SLR lenses offer a wider aperture range and larger maximum aperture typically f/1.4 to f/1.8 for a 50 mm lens. This allows photographs to be taken in lower light conditions without flash, and allows a narrower depth of field, which is useful for blurring the background behind the subject, and making the subject more prominent. SLR lenses are manufactured with extremely long focal lengths, allowing a photographer to be at a considerable distance away from the subject and yet still expose a sharp and focused image.