Abstract: A stereomicroscope for comparing photographs is disclosed. The microscope includes a pair of complementary occluders with one occluder positioned in an intermediate image plane of each side of the stereo optical system, which also includes a conventional image rotator and zoom system to permit independent adjustment of the orientation and size of each image. The complementary occluders accentuate small differences between nearly identical photographs by providing a border at which an object present in only one photograph will appear or disappear as the two photographs are simultaneously scanned.