Unlike a compound light microscope, illumination in a stereo microscope most often uses reflected illumination rather than transmitted (diascopic) illumination, that is, light reflected from the surface of an object rather than light transmitted through an object. Use of reflected light from the object allows examination of specimens that would be too thick or otherwise opaque for compound microscopy. Some stereo microscopes are also capable of transmitted light illumination as well, typically by having a bulb or mirror beneath a transparent stage underneath the object, though unlike a compound microscope, transmitted illumination is not focused through a condenser in most systems. Stereoscopes with specially-equipped illuminators can be used for dark field microscopy, using either reflected or transmitted light.
Great working distance and depth of field are important qualities for this type of microscope. Both qualities are inversely correlated with resolution: the higher the resolution (i.e. the greater the distance at which two adjacent points can be distinguished as separate), the smaller the depth of field and working distance. Some stereo microscopes can deliver a useful magnification up to 100×, comparable to a 10× objective and 10× eyepiece in a normal compound microscope, although the magnification is often much lower. This is around one tenth the useful resolution of a normal compound optical microscope.
The large working distance at low magnification is useful in examining large solid objects such as fracture surfaces, especially using fibre-optic illumination. Such samples can also be manipulated easily so as to determine the points of interest. There are severe limitations on sample size in scanning electron microscopy, as well as ease of manipulation in the specimen chamber.