A method of forming a shadowgraph image is described, comprising the steps of illuminating a glazing (52), e.g., a vehicle windscreen, with light from a localized light source (50), said light being expanded and collimated by a lens optical system (54) or a mirror optical system, forming a virtual shadowgraph image of the glazing in a virtual image plane (56), which may be positioned behind or in front of the glazing: and imaging the virtual image onto a CCD camera (62). The glazing may be moving relative to the light source or may be stationary. Furthermore, a method of glazing inspection is described, comprising forming a shadowgraph image as outlined above; processing the shadowgraph image to exclude measurement points corresponding to obscure areas of the glazing as non-valid measurement points: obtaining a processed image by determining an illumination value for each valid measurement point; constructing a reference image by scanning a convolution window point by point over the processed image; and comparing the illumination value of the corresponding point of the reference image.