GB749725A - Improvements in or relating to exposure meter - Google Patents

Abstract

749,725. Photo-electric exposure meters. GOSSEN & CO., GES., P. Nov. 20, 1953 [Nov. 24, 1952], No. 32260/53. Class 40 (3). [Also in Group XX] In a photo-electric exposure meter, light intensity values measured by the meter are indicated on a first scale and one part of a transversely divided rotatable roller is provided with light intensity values corresponding to those on the first scale while a second part of the roller is provided with axial rows representing aperture. The two parts of the roller are relatively adjustable to take account of film speed and then locked together so that when the first part of the roller is rotated to a " light " value corresponding to that indicated by the exposure meter the various aperture values in the second part of the roller may be read against corresponding shutter speeds. As shown, Fig. 1, light received through a transparent honeycomb element (not shown) on the top of the meter causes a photo-electric cell (not shown) to position the pointer 5 of a moving coil meter. The scale 7 associated with this pointer is in twelve divisions and twelve corresponding divisions are provided on the edge periphery of the portion 12b of the composite roller shown in Fig. 6. This roller is rotated until the speed, corresponding to that indicated by pointer 5 appears in a window on the front of the instrument. The section 11b of the roller carries a number of parallel axial rows of figures representing aperture settings, one row at a time being visible through a window in the front of the instrument. In use the two sections of the roller are adjusted relatively to each other to take account of film speed by depressing plate 13 on the end of spindle 11a. This releases pins 12a on section 12 of the roller from depressions in the other section 11 allowing them to be rotated relatively to each other until the pins engage other depressions. End plate 13 is calibrated in film speeds which are brought to correspond with a fiduciary mark on knob 12. The roller as a whole is then rotated by knob 12 to bring the light intensity corresponding to that shown by the photo-electric exposure meter to show in window 12b. The various values of aperture may then be read against corresponding shutter speeds 18. The aperture and shutter speed markings may be transposed.