A method of digitizing an analog quantity from an electromagnetic radiation detector including a matrix of juxtaposed elementary sensors, including, for each line or column of the matrix, the steps of: integrating the analog quantity using an integrator stage; converting the integrated analog quantity to a first numerical value via a binary counter and a memory element connected to the output of a comparator stage; converting the first numerical value to an analog signal via an analog-to-digital converter; subtracting the analog signal from the analog quantity to be digitized; amplifying the signal resulting from the subtraction with a gain representing the first numerical value; integrating to produce a second numerical value proportional to the analog signal thereby amplified and forming a second binary number representing the least significant bits; and adding said first and second numerical values to form a number representative of the analog quantity to be integrated.