1. A method for correcting repeated Fixed Pattern Noise (FPN) from a digitally encoded image captured with an image sensor, comprising an array of active pixels arranged in Y rows and M columns, at least one row comprising optically masked pixels which are shielded from incident radiation, so that the output image signals obtained from each at least one optically masked pixel in a column represent column FPN of the corresponding column, the method comprising: recording into at least one L-size line memory the values indicative of the column FPN for L corresponding columns of the array; for each at least one L-size line memory, averaging the column FPN values into a smaller N-size noise memory, wherein position n t of N-size noise memory includes a value indicative of the average of the column FPN values from the positions yN+t of the L-sized line memory for each integer value of y, wherein 0<=y<=L/N−1 and 0<=t<N; reading the pixel image signals from the array of active pixels; and adjusting the read pixel image signals according to the averaged column FPN values of the at least one N-size noise memory.