Buy magnifier lenses from Grainger. 10D swing away magnifier lens are for indoor use only and can be used for close-up inspection, assembly, rework, and general small area applications. Pocket stereoscopes Distance between lenses are adjustable from 56mm to 75mm. Mirror Stereoscopes are for viewing and interpreting aerial photographs. They offer an optical path of 27cm and a field of view of 18cm x 24cm.