An image sensor for gathering images at one and the same time at low illumination level and at high illumination level is described. The sensor operates with a double integration time at each frame. Two successive charge transfers from a photodiode to a storage node are performed, the first after a first duration, the second after a second duration different from the first. The potential of the storage node after the first transfer of charge is sampled in a first capacitor of the reading circuit. The potential after a reinitialization of the storage node is sampled in a second capacitor. A level of potential taken after the second transfer is conditionally resampled in the first capacitor. The condition of the resampling is a condition of signal level after the first transfer. This level is applied to the differential amplifier of a ramp-type converter for a short duration of ramp.