Wavefront reconstruction techniques are used to produce a shearing interferogram of an object. The desired shear of the object is produced by birefringent elements which make it possible to record simultaneously two holograms on a photographic plate. This avoids the errors due to the instability of the recording apparatus which are usually present when two exposures are made successively. The method is applicable to stationary phenomena and to those transient phenomena which change inappreciably during the time of exposure.