GB361000A - Improvements in photographic exposure meters - Google Patents

Abstract

361,000. Exposure meters. BERTRAM, E., 15, Planeggerstrasse, Pasing, near Munich, Germany. Aug. 20, 1930, No. 24928. Convention date, Aug. 20, 1929. [Class 98 (i).] An exposure meter of the viewing telescope type has (1) a tube fitted internally with an annular light filter graduated for measuring degrees of luminosity and having externally thereon a corresponding light value scale and also a series of exposure columns ; and (2) a rotatable outer cylinder having a slot one edge of which is marked with appropriate diaphragm apertures and which is set to the light value scale, the slot exposing one of the exposure columns. The light value scale can be on a ring adjustable on the tube according to plate speeds. The tube 2, Fig. 1, is fitted internally with a central focusing screen 1 on which the viewed image is focused by a lens 20. The annular light filter comprises a series of overlapping translucent plates 7 and a plate 9 marked with numbers (1-14) which are visible through an annular series of openings 3<1> under diffused light conditions by means of a ground glass ring 8. The tube 2 carries a ring 15, Figs. 1 and 4, having a corresponding light value scale (1-14). The tube also carries a series of exposure columns 10. A rotatable outer tube 14 has a setting pointer 26 and carries a slotted cylinder 11 the edge 13 of the slot having a column of lens apertures. The slotted cylinder is covered by a protecting cover 11<1>. For plates of different speeds the ring 15 may be rotatable on the tube 2 and set by means of a plate speed scale 151 against a mark on a ring 17 fixed to the tube 2, the ring 15 being held by a spring catch on the ring 17 engaging one of a series of notches 16 in the ring 15. The tube 2 is also fitted with a sliding eyepiece tube 22.