Improvements in Apparatus for Calculating Photographic Exposures.

6380. Wynne, G. F. March 13. [Cognate Application, 16,258/14.] Exposure meters and actinometers.-Relates to exposure-calculating apparatus of the type comprising an actinometer and calculating-scales contained in a case of watch shape. The case consists of two parts 1, 2, Figs. 1, 4 and 5, hinged together at 3 and provided with a spring catch 5, 6, the part 1 containing the actinometer parts and the part 2 the calculating- scales. A stationary sheet of sensitive paper is placed in the bottom of the part 1, and over it is placed a removable rotary dish plate 7, Fig. 6, which is normally retained by the engagement of projections 20 under a flange 8, Fig. 5, and is provided with a slot or window 10, through which different parts of the paper can be exposed by turning the dish plate 7 by means of a milled edge 9. Standard tints 14, Fig. 1, are painted on each side of the slot 10, and are protected from dirt by a transparent disk 13, Fig. 6, above which is an opaque disk 11 having a circular window 12. In order to prevent colouring of the sensitive paper while the dish plate 7 is being turned, the window 10 is covered by the fingers, the movement of radial divisions 22, Fig. 1, on the disk 11 past a fixed point indicating when the plate 7 has been turned through the required angle. The calculating scales are formed on disks 23, 24, Figs. 1 and 4, and the disk 24, which is rotated by means of a knob 26, is detachably fitted by snapping over an enlarged pivot knob 25, so that interchangeable scales can be employed.