GB880623A - Lubrication of the depth of field in photographic objectives - Google Patents

Abstract

880,623. Depth of field indication in photographic objectives. SCHNEIDER, M. C. April 8, 1959 [April 17, 1958], No. 11833/59. Class 98(1). A photographic objective has means for indicating two sets of depth of field limits for each of a number of diaphragm settings, the limits of one set corresponding to a smaller circle of least than the other. In those objectives in which the depth of field is indicated by means of a set of stationary depth of field graduations co-operating with a rotatable focusing scale, a second set of such graduations preferably in a different colour and indicating wider limits, may be either superimposed on (Fig. 1 not shown) or provided along side (Fig. 2 not shown) the first. In the second of the two alternatives the two sets of depth of field graduations are circumferentially spaced around a member rotatably mounted on the objective and adjustable to either of two predetermined angular positions according to which set of graduations it is desired shall co-operate with the focusing scale. In a modification (Fig. 3 not shown) the two sets of depth of field graduations are only provided with one set of reference numerals but two sets of leading lines indicate the alternative limits of the depth of field on the focusing scale. In a mechanical embodiment shown in Fig. 4 two rings e and f are rotated in opposite directions when a diaphragm setting member (not shown) is adjusted and respectively carry two masking plates g and h, the edges g<SP>1</SP> and h<SP>1</SP> of which indicate limits of the depth of field by uncovering varying amounts of an underlying focusing scale (not shown). Additional plates i and j for indicating a second set of depth of field limits are controlled respectively by two levers k and l, which are respectively pivoted on the rings e and f and co-operate with stationary cams m and n. In the embodiment shown in Figs. 5 and 5a a plate p bearing stepped graduations p<SP>1</SP> is mounted in known manner on objective o so as to be axially displaced by adjustment of a diaphragm aperture setting ring s, two different portions of said graduations being visible in the spaced windows q and q<SP>1</SP> for indicating two sets of depth of field limits on a rotatable focusing scale r<SP>1</SP>. In modifications of this embodiment, the plate p may carry two sets of differently coloured graduations p' which are made visible in a single window on the objective, and the stepped graduations may be replaced by line graduations.