Abstract: Apparatus and method for temporal comparison of skin surface images which is fully automatic and based on robust parameters, using a CCD camera provided with telecentric optics to enabling the capture of images with constant magnification independent of the camera-object distance. The camera is linked to a PC with a frame grabber for storing the image and processing means for calibrating light and for calculating statistics of the image. The illumination source provides a homogeneous illumination of the skin, and the light is calibrated by transforming an acquired image into the model image which would have resulted if illumination of the object were solely by the reference (white) light. Three monochromatic images are produced, one for each of three color channels. The three images are grabbed and processed, and a combination of these three images gives the true color (red, green and blue or RGB) image.