The camera is not unlike the conventional 8x10inch view camera. It is „cone-shaped," being about 5 inches square at the lens end and about 12 inches square at the plate end, and is 30 inches long. The small end has two lens rings mounted one above the other. Actually the comparison camera consists of two rigid camera enclosures mounted one above the other with an adjustable horizontal dividing septum to be described later. The lens rings carry a matched pair of Bausch and Lomb lenses. Lenses with various focal lengths are available; a pair of 112
mm. Tessar Ic lenses are used for low magnifications, a pair of 70 mm. focal length Micro Tessars for greater magnification, and even 48 mm. Micro Tessars may be used. The unique feature of the camera body is the fact that it contains an adjustable thin metal partition dividing the camera horizontally into two separate parts, one for each lens. This partition is surfaced with sateen cloth and sprayed with instrument black (a nonglossing lacquer) to prevent halo and ghost images, as the angle of incidence is very low, less than 15° at times. There is no reflection from this metal partition. It is slip-hinged at the lens end and supported at the plate end by two bearing blocks through which run two threaded vertical rods, one at each side of the plate holder but out of line with the light path. A single control knob (D in Fig. 65) at the top of the rear end of the camera permits the adjustment of this dividing partition up or down, the two threaded rods being rotated at the same rate by means of a connecting chain and sprocket drive. The movement of the partition permits the making of comparisons of specimens at any point in their length. The rear of the camera is fitted with a conventional 8x10-inch plate back with ground glass, permitting the use of standard 8x10-inch cut film or plate holders.
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