GB831035A - Stop rationer for photoengraving camera - Google Patents

Abstract

831,035. Camera with f-value and enlargement ratio scales. POWERS CHEMCO. Inc. April 30, 1958 [July 19, 1957], No. 13819/58. Class 98(1) A camera adapted to produce negatives of different sizes relative to the copy has an adjustable diaphragm aperture controlled by a rotatable ring, said ring being connected to a rotatable member which has associated with it (and with each other) two scales: a negative-to-copy-sizeratio scale, and an f-value scale, so that corresponding values on the two scales may be set or read against each other directly. As shown, ring 24, which controls the aperture, is connected by a driving belt 48 to a sheave 38 of a drum assembly 32, all these members being supported on a plate 14 bolted to the camera. Thus by turning the knurled knob 44 of the drum, the aperture is altered. A fixed scale 56, graduated to indicate the enlargement or reduction ratio, is secured to plate 14, and lies adjacent the surface of the drum. On the drum surface itself is a series of graduations corresponding to various f-values. When developed on a flat surface (Fig. 7, not shown) these graduations are a series of straight lines. When disposed round the drum periphery, they form helical lines, as shown. Thus as the aperture is varied by turning drum 32, corresponding values of enlargement ratios and f-stops can be read against each other directly.