an image sensing system includes a solid - state image sensor having at least two horizontal shift registers for providing monochromatic multichannel signals , and a signal processing circuit for combining the signals into a monochromatic composite signal . the signal processing circuit includes a first combining circuit for producing a first output signal by selecting one of the multichannel signals alternately at regular intervals , a second combining circuit for adding together the multichannel signals to produce a second , and a third combining circuit for producing a composite signal by output signal combining the first and second signals through selection or addition . thus , this system can produce the composite signal in either of two different combining modes , one of which is superior in frequency characteristic and the other of which can provide high s / n signals .