Microscopes magnify subjects using two lenses. The first stage of magnification is produced by the objective lens and the second stage of magnification is the eyepiece. An objective lens has a focal length just like traditional photographic lenses that are used on a DSLR camera. Working distances are very small for this type of photography—a typical range of objective magnifications for a light microscope might include a 2x, 4x, 10x, 20x, 40, 60x or 100x. I pick my lens on the microscope based on the sample’s magnification requirements. Magnification influences the image’s depth of field, so a big thick sample (.5cm) benefit from low magnification, while very flat subjects need more magnification.