For auto-focusing of a focusing lens within an image sensing system, an N-bin luminance histogram is generated by a digital signal processor from an image. A microprocessor determines a type of the image from the N-bin luminance histogram. The microprocessor also determines a focus position using a first set of at least one focus value if the image is determined to be of a first type. The microprocessor also determines the focus position using a second set of at least one focus value different from the first set if the image is determined to be of a second type.