Twin-Lens Reflex Camera

Twin-Lens Reflex Camera

  • The twin-lens reflex (TLR) camera, formerly the mainstay of magazine photographers for many years, remains popular with both professional and amateur photographers. It is most commonly used in the 21/4 x 21/4 inch format, but can be had in formats as small as 35 mm or as large as 4 x 5 inches.
    Twin-lens reflex cameras can vary in shape and proportions and this type of camera is basically two box-body cameras placed one atop the other, with one mechanism controlling the focusing of the two lenses. The lower lens, the "taking" lens, forms the image directly on the film, while the upper lens, the "viewing" lens, has its light path deflected upward to a horizontal ground glass viewing screen. This screen is usually protected by a collapsible hood to prevent stray light from obscuring the image.

  • Within the hood is a folding magnifier, which aids in accurate focusing when it is swung into position over the ground glass. In operation, the photographer holds the camera at waist or chest level, looks into the top of the camera while framing and focusing the image, and makes the picture when ready.

  • The viewing lens has no shutter, and usually no iris diaphragm. The shutter mechanism on the taking lens is of the between-the-lens leaf type, with the diaphragm incorporated in it. The twin-lens reflex combines certain features of both the rangefinder and SLR designs. In one sense it is a rangefinder camera with an exceptionally large viewfinder; in another sense it is a reflex design, but with the mirror permanently out of the taking lens light path, so that it requires its own image-forming lens.

  • The twin-lens reflex is not an inherently versatile camera, but it does have certain advantages. It is an exceptionally easy camera with which to learn basic photography. Most people find it easy to handle and pleasant to operate. The shutter is almost noiseless, and the waist-level viewing position makes it quite inconspicuous to use. (For instance, it is well out of sight from the side when hanging by its neck strap between the flaps of an open coat or jacket.) The 21/4 x 21/4 inch negative is larger than 35 mm, an advantage with respect to image quality. The shutter is readily synchronized to any type of flash at any speed. The viewfinder is usually large and brilliant.

  • There are several disadvantages. Most models come with lenses of only one focal length and are without provisions for interchanging. A very few types offer limited interchangeability of lenses, with pairs of matching lenses being mounted on a single interchangeable front plate. Obviously, such interchangeability is limited to lenses made for the specific camera, and is expensive because lenses must be in matched pairs. The alternative, is use two cameras with different lens types, is not entirely satisfactory, either. It is annoying to have more than one camera hanging about one's person at any given and doing so requires care to prevent damage from banging them together. So having two complete cameras with different lenses is less than satisfactory, as well as being expensive.

  • Depth of field cannot be checked directly on the ground glass unless a diaphragm is on the viewing lens-and this is seldom the case. Waist-level viewing results in "seeing the world through one's navel," often not a suitable angle of view. In addition, the simple mirror-type viewer of most twin-lens reflex cameras reverses the image laterally, which, by reversing the apparent direction of cross-axis movement, makes following fast motion quite difficult. This angle-of-view problem can be partially corrected by use of a "sports viewfinder," a simple open frame and peepsight device built into the viewer hood. A few twin-lens reflex cameras can be equipped with a prism or other optical system that erects the image to allow eye-level viewing and corrects the lateral reversal. But the sports viewfinder makes accurate framing chancy while removing all possibility of judging the depth of field, and the eye-level prism increases the camera's weight, bulk, and cost.

  • Close-up subjects can be photographed only when slip-on supplementary lenses are added. These lenses, however well made, tend to degrade the image, and usually require additional special devices to aid in accurate composition and focusing. The viewing and taking lenses being separated in space, the two separate angles of view produce image displacement or parallax. There is no difficulty in long-distance viewing, and relatively little at intermediate distances. But there is too much parallax in the twin lens viewing system for accurate viewing at really close distances. The more expensive cameras feature built-in parallax correction; the viewing lens is canted forward to include the same field of view in the plane of prime focus as the taking lens. This still does not provide an identical angle of view, and thus the foreground-background overlaps will differ in viewing and on the film. Even where correction is provided, and where it remains satisfactory in use, it is usually operative only down to about three feet from the lens. At closer distances the only real way to avoid parallax problems is to make use of a vertical-shift device on a tripod after composing and focusing, to place the taking lens in the former position of the viewing lens before exposing the film.

  • The subject area in which the twin-lens reflex camera is most at home is the photography of people and their surroundings. As stated earlier, it has done noble service in magazine illustration, and has also done yeoman service in field ethnology in the last several decades.

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