This note deals with some gemological applications for a tool well known to microscopists: the first-order red compensator. In gemological microscopy, the compensator can be useful in locating interference colors and optic figures in birefringent materials and in delineating strain in gemstones. In polarized light photomicrography, a properly positioned compensator can reduce the exposure time required and thus the risk of film reciprocity failure and of poor-quality images resulting from random vibrations of the microscope and its accessories.
