A photographic facsimile of a line image at a predetermined orientation is illuminated by a collimated monochromatic light source to produce a diffraction pattern. The diffraction pattern is focussed by a converging lens to image the Fourier transform of the line image on a spatial frequency plane. The image in the spatial frequency plane is applied to a detector for measuring the spatial power distribution as a function of the spatial frequency. The line image is then reoriented in the image plane, and successive measurements made as the image is rotated in the image plane. Resolution is quantified in the spatial frequency plane as the magnitude of a selected signal as a function of displacement (i.e, spatial frequency). By simulating selected imaging components and generating a resultant line image, the resolution of any imaging system component may be measured.