In light microscopy, dark field and interference contrast are widely used for examination of transparent specimens. These methods both suffer from various limitations when photomicrographs have to be taken from fine details, especially in three-dimensional specimens requiring a large depth of field.
In common dark field illumination, the condenser either is not equipped with an aperture diaphragm, or an existing condenser diaphragm has to remain in the wide-open position. Thus, the depth of field is lower than in bright field images. Moreover, dark field imaging is associated with marginal blooming, especially in linear structures exhibiting with large differences in phase or density (e.g. cell walls, edges in crystals and other mineralogical material).