Machine vision is the ability of a computer system to recognize object shapes, size, color, or distance to some point. Here we present a system capable to recognize the size of an object as well as its distance to an observation plane, by using the shadow that the object produces on this plane. The shadow is formed by a dark zone called umbra and an intermediate zone between the dark zone and the bright one called penumbra. The penumbra is used to correlate the diameter of the object producing it and the distance to the plane where the shadow is projected. The system is capable of measuring milimetric dimensions, with a precision of tenths of a milimeter,and to evaluate its distance to the plane with the same precision. MATLAB is used as the computing engine. Experimental results are reported.