1,218,318. Photographic apparatus. POLAROID CORP. Oct.6, 1969 [Oct.7, 1968], No.48930/69. Heading G2A. The exposure control system of photographic apparatus is arranged to take into account the reflectivity of a subject to be photographed, and of its environment, as well as the distance of the subject from the apparatus, before exposing photosensitive material in the apparatus to the subject which is artificially illuminated during the exposure. The exposure control system is generally set in accordance with the subject to apparatus distance, and then a correction applied depending on the reflectivity and also on the distance, a photosensitive metering technique being used to derive an integrated valuation of the reflectivity. The exposure may be controlled by adjusting the aperture, by altering the exposure time, by controlling the light output from the source of artificial light, or by any combination thereof. In the embodiment shown, the inverse square law input to the exposure system is provided by an aperture adjustment, and the reflectivity correction is provided through the use of an optical wedge 48 of varying density. Diaphragm blades 50, 52 are set by manipulating a control knob 56, and are adjusted thereby until an index pointer 74 on the blade 50 is opposite the appropriate range marking on a flanged section 72 of the blade 52. The reflectivity correction factor is obtained by illuminating the subject with a metering flash 76. Reflected light is received by a photodetector 82, is integrated, and a signal is presented to an automatic gain control (A.G.C.) circuit 88, which also receives a signal from a range factor 90 in dependence on the setting of the pointer 74 and section 72. The output of the A.G. C. 88 is fed to the drive 93 of the optical wedge 48. The exposure is then made using light source 100, and the wedge 48 is reset to a position removed from the exposure aperture of the apparatus.
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