1. A procedure for the detection of the impression (I) made on a specimen (P) in measuring the hardness at penetration, and in particular for the determination of the position of the characteristic points of said impression, for example, the vertices in the Vickers impression, in which the specimen is illuminated so that it creates, in the vicinity of the impression, a variation of the luminance with respect to a neighbouring zone, and in which the image (R) of the impression is then magnified by an optical system (OS), said procedure further including the following operations: exploring, by optical/electrical converter means (VC; C) the region (R) of the magnified image of the specimen (P) carrying the impression (I) in order to generate image electrical signals carrying information (L) indicative of the luminance of the explored region (R), drawing from said image signals, by means of a technique of image processing, position data indicative of a group of image points taken, on the basis of predetermined selection criteria, as belonging to the impression contour (I), and extrapolating or interpolating, from the position data of at least some of said image points, the position of the characteristic points of said impression.