GB187077A - An improved automatic indicating device for use on extending cameras - Google Patents

Abstract

187,077. Rickman, W. G. Aug. 16, 1921. Enlarging, copying, and reducing; exposuremeters.-An indicator which is automatically operated on extending the camera is provided to indicate data which alter with the extension of the lens beyond the infinity point or stop, as, for example, the reduced F-value of the lens aperture, the change of exposure required, the degree of enlargement or other data. The indicator may consist of a pointer rotating with relation to a fixed disc as in Fig. 6, or of a disc rotating behind a slot as in Fig. 26, or of a blind or a simple roller moving behind a slot as in Fig. 37. The mechanism for rotating the disc or pointer comprises a cord &c. G secured adjustably to the bellows by an adjustable drum S, Fig. 2, adapted when the bellows is extended to rotate a drum F, Fig. 8, round which it is wound against the action of a spring enclosed in the drum. This motion is transmitted through cogs E, C, to a dial H, of which the markings are visible through a slot A<2> in the lid of the indicator container A. In this form a second indicator disc K may be mounted on the outside of the indicator case A on a boss J, Fig. 28, the boss carrying also an adjustable pointer L<2> with reference to which the inner indicator disc H rotates. The zero or normal mark on this inner disc acts as a moving pointer for the outer indicator disc. A magnifying lens L<1> may be secured in the boss J to facilitate the reading of the inner indicator. The external indicator may be used alone, in which case the inner indicator is replaced by a pointer. The roller blind indicator, shown in Fig. 37, is operated similarly by a drum F and cogs E, C, and is arranged to have its zero adjustable by moving the cog C out of engagement with the cog E against the action of spring Q. The roller indicator is arranged as shown in Fig. 38. Various arrangements of the lens data on the indicators are shown on the drawings, and the camera may be provided with a number of interchangeable indicators corresponding to lenses of different focal lengths, the data shown being the F ratios, the various degrees of enlargement or reduction, the positions of conjugate focus, and the duration of exposure compared with that for a like aperture at infinity point or with that necessary for copying full size.