Diaphragms and plates were examined with a speckle-shearing interferometer which utilized a split lens both for imaging and shearing functions. It was found that the location, shape and size of the defect could be ascertained accurately under certain conditions. The experiments showed that the fringe pattern of a defective diaphragm under pressure loading could be simulated on a good diaphragm by subjecting it to a combined loading (pressure and a concentrated load) with the proper shear orientation. However, in extreme situations - not likely to occur in practice - a defect could behave as a mini diaphragm with an elastic boundary. Lens aberrations degraded the contrast of slope fringes considerably. © 1982.