A solid-state image sensor (1) with very high sensitivity approaching the single-photon limit is realized with three modular building blocks: (a) a pixel (2.11, 2.12, . . . ) with a photo-site, intermediate photo-charge storage capability as used for correlated double sampling, and an electronic circuit for signal buffering or amplification, (b) a column or row signal line (3.1) to which a plurality of such pixels (2.11, 2.21, . . . ) is connected using transistor switches, incorporating a low-pass filter (30.1), and (c) a readout circuit (4) to which the row signal lines (3.1, 3.2, . . . ) are connected, consisting of a plurality of analog amplifiers (41.1, 41.2, . . . ) with an analog multiplexer (42). Photo-generated signals are read out and the reset level is subtracted either in the analog or in the digital domain, to implement a correlated-double-sampling method.