Text for ISO/IEC FCD 14496-1 Systems

A method and apparatus capable of measuring light which has a flickering component. The light which is to be measured is received simultaneously by a pair of photosensitive units each of which provides a signal having an AC component corresponding to the flickering light component and a DC component corresponding to the steady light component. One of the signals produced by one of the photosensitive units is electrically altered in such a way that its AC component will cancel the AC component of the other signal when arithmetically combined therewith. Then the arithmetic combining of the signals is carried out so that the AC components will cancel each other, thus leaving only a DC output which can then be used for purposes such as operating a light meter or participating in the control of the operation of a camera shutter.