Method and apparatus for controlling exposure by selective use of blocking visible filter

Abstract From the Canadian patent

Method and apparatus for automatically controlling exposure of a photographic film by evaluating non-visible spectral scene light frequencies. Particularly for artificially lit scenes, an evaluation of predominantly infrared frequencies is preferred. In one embodiment the, IR scene lighting is evaluated under control of the shutter aperture system while in another embodiment the strobe, itself is controlled by its own photodetector responsive to IR scene light.