1. A method of reducing an amount of fixed pattern noise from an image signal generated by an image sensor, comprising: for each operational pixel in the image signal, applying a recursively updated offset term to generate a corrected image signal; and recursively updating the offset correction terms by: spatially filtering the corrected image signal for a current frame of the image signal; comparing the filtered corrected image signal of the current frame with a spatially filtered corrected image signal of a preceding frame of the image signal; and updating the offset correction terms with terms generated as a function of the comparison.