1309771 Photo-electric electronic flash control PONDER & BEST Inc 6 March 1970 [7 March 1969 27 June 1969 22 Sept 1969] 10883/70 Heading G1A A light-sensing device comprises a light receiving lens arrangement elements of which have different focal lengths and fields of view of different magnitudes which are substantially concentric and photo-electric means associated with the lens arrangement for receiving simultaneously light from all the elements. The lens elements may be coupled to the photo-cell arrangement by a fibre optic light guide and the cell output where there are a plurality may be connected in series or parallel. The light from side-by-side lenses 2202, 2203, Fig. 13, falls on sensor 2201 or, light from concentric lens elements 2302, Fig.14, may fall on sensor 2301. Alternatively the light may fall on separate sensors. The device is used in an electronic flash control arrangement and in one arrangement a movable light guide may serve for directly reflected light or for bounced light. The flash circuit arrangements which are those disclosed in Specification 1267234 may additionally incorporate a switch for half or full flash, and/or a switch whereby the flash may respond as a "slave" to a flash from a master and subsequently be controlled as regards quantity of measured reflected light for extinguishing the flash. The extinguishing tube may be gas filled and include one or more low voltage triggering electrodes or may be fired by a light pulse from a gallium arsenide diode.