Abstract: A passive method for selecting the best focal position from a plurality of focal positions for a lens focussing on an image in a field of view is disclosed. The lens forms an image at a first position. The image is segmented to form a plurality of pixels. A histogram of the intensity of light at each of the pixels in the image is determined. A cumulative histogram is developed therefrom. A sharpness value is determined from the cumulative histogram. The sharpness value is the intensity of light that corresponds to the smallest cumulative pixel number having a non-zero intensity of light value. The lens is then moved to a new position and another sharpness for the new position is determined. From the plurality of positions moved by the lens, the smallest or lowest sharpness value is chosen and the position that corresponds to that smallest or lowest sharpness value is the position that represents the best focal position.