A method for image acquisition and conversion includes low-pass filtering an image by an acquisition lens, producing from the low-pass filtered image, an up-sampled image with a first resolution with an up-sampling factor using a image sensor. The up-sampled image is converted into a multi-level image with a second resolution lower than the first resolution with an image processing circuit. The converting depends on the low-pass filtering of the lens and on the up-sampling factor. The method is adapted to gigapixel sensors and convention image sensors.