Electro-optical sensing of form, type and other defects on surfaces such as sheet metal or plastic panels. Method and apparatus are disclosed for detection and quantification if defects such as dents, creases, low spots, flat spots, etc. which are a result of the manufacturing, material handling and assembly process. In one embodiment (Fig. 2) the sensing apparatus includes a light source (10) for illuminating an area of the surface (11) to be inspected. A retroreflective screen (15) is positioned relative to the surface (11) so that light reflected from the surface (11) is retroreflected back to the surface (11) to be reflected therefrom. A lens (21) images the returning light onto a detector (22).