Ramp-type analogue-digital conversion, with multiple conversions or single conversion, depending on the light level received by a pixel

A method for reading a pixel in a matrix image sensor, the pixel providing on a column conductor a voltage level representing a light level received by the pixel, and the method of reading comprising an analogue-digital conversion by means of a ramp-type converter comprising a comparison of the voltage level received from the column conductor with a linear analogue voltage ramp by means of a comparator, and a counting of clock pulses between an instant of ramp start and an instant of toggling of the output of the comparator,

• wherein the method of reading comprises a phase of detecting the toggling of the output of the comparator after a predetermined time after the instant ramp start, to discriminate between a high light level, if the output has not toggled, or a low light level, if the output has toggled and convert the voltage level in accordance with respectively a first or a second mode of conversion where
• the first mode of conversion comprises a single counting by the counter in the course of a nominal conversion time window with the aid of a ramp of nominal duration allowing the conversion of a high light level,
• the second mode of conversion comprises the establishment of n successive ramps of reduced duration over the duration of the nominal conversion time window, with for each ramp, a counting by the counter between the start of the ramp and the toggling of the output of the comparator, and a summation of the n counting results, where n is an integer greater than 1.