Method of reading an image sensor signal and image sensor

The invention relates to matrix-array image sensors with MOS-technology active pixels, comprising a matrix-array of pixels arranged in rows and columns. To read the signal from a pixel, the reset potential present on a column conductor is sampled in two capacitors. The first capacitor is linked to an input of a comparator; the other input receives, through the second capacitor, a linear voltage ramp varying in a first direction for a first duration, then a linear voltage ramp in the reverse direction; a digital value N of the time between the start of this second ramp and the switching over of the comparator is counted; the useful potential present on the column conductor and representing the lighting of the pixel is sampled again, but in the first capacitor only; two ramps identical to the preceding ones are applied to the second input, through the second capacitor; a digital value N′ of the time between the start of the second reverse ramp and the switching over of the comparator is counted, the difference between the two counts N and N′ representing a measurement of the lighting of the pixel.