Reflex cameras Reflex cameras, both the SLR and the TLR types, are equipped with mirrors that reflect in the viewfinder the scene to be photographed. The twin-lens reflex is box-shaped, with a viewfinder consisting of a horizontal ground-glass screen located at the top of the camera. Mounted vertically on the front panel of the camera are two lenses, one for taking photographs and the other for viewing. The lenses are coupled, so that focusing one automatically focuses the other. The image formed by the upper, or viewing, lens is reflected to the viewing screen by a fixed mirror mounted at a 45 degree angle. The photographer focuses the camera and adjusts the composition while looking at the screen. The image formed by the lower lens is focused on the film at the back of the camera. Like rangefinder cameras, TLRs are subject to parallax. In the SLR type of reflex camera, a single lens is used for both viewing the scene and taking the photograph. A hinged mirror situated between the lens and the film reflects the image formed by the lens through a five-sided prism and onto a ground-glass screen on top of the camera. At the moment the shutter is opened, a spring automatically pulls the mirror out of the path between lens and film. Because of the prism, the image recorded on the film is almost exactly that which the camera lens “sees,” without any parallax effects. Most SLRs are precision instruments equipped with focal-plane shutters. Many have automatic exposure-control features and built-in light meters. Most modern SLRs have electronically triggered shutters; apertures, too, may be electronically actuated or they may be adjusted manually. Increasingly, camera manufacturers produce SLRs with automatic focusing, an innovation originally reserved for amateur cameras. Minolta's Maxxum series, Canon's EOS series, and Nikon's advanced professional camera, the F-4, all have autofocus capability and are completely electronic. Central processing units (CPUs) control the electronic functions in these cameras. Minolta's Maxxum 7000i has software “cards” which, when inserted in a slot on the side of the camera, expand the camera's capabilities. Autofocus cameras use electronics and a CPU to sample automatically the distance between camera and subject and to determine the optimum exposure level. Most autofocus cameras bounce either an infrared light beam or ultrasonic (sonar) waves off the subject to determine distance and set the focus. Some cameras, including Canon's EOS and Nikon's SLRs, use passive autofocus systems. Instead of emitting waves or beams, these cameras automatically adjust the focus of the lens until sensors detect the area of maximum contrast in a rectangular target at the center of the focusing screen.

      

SLR Camera Anatomy Single-lens reflex, or SLR, cameras are among the most common in use today. Single-lens reflex means that the same lens is used for viewing and taking the photograph. The moveable mirror between the lens and the film reflects the image on a ground-glass viewing screen while the user adjusts the focus. When the shutter release button is depressed, a spring pushes the mirror out of the way, and the image is recorded on the film. The cameras are popular because users have the option to control elements such as shutter speed, focus, and aperture manually or automatically. This option allows photographers to achieve a wide variety of effects with relative ease. The quality of SLR camera pictures is generally superior to that of the so-called point-and-shoot camera.

      

Rangefinder cameras Rangefinder cameras have a viewfinder through which the photographer sees and frames the subject or scene. The viewfinder does not, however, show the scene through the lens but instead closely approximates what the lens would record. This situation, in which the point of view of the lens does not match that of the viewfinder, results in what is known as parallax. At longer distances, the effects of parallax are negligible; at short distances, they become more pronounced, making it difficult for the photographer to frame a scene or subject with certainty.

      

Pinhole Camera A simple camera can be built by making a pinhole in a box. Light passes through the hole and forms an inverted, backwards image of the subject on the back of the box. The image will be somewhat dim, but the detail sharp enough that properly placed film will produce a good photograph. However, this kind of photography only works if the film receives absolutely no other light.

      

Microsoft Illustrations & Litureature Courtesy of: "Photography," Microsoft (R) Encarta. Copyright (c) 1994 Microsoft Corporation. Copyright (c) 1994 Funk & Wagnall's Corporation. UNIQUE VISITORS