SeeNano versus Differential Interference Contrast
This method operates with a shifting axis where the same contours are shifted two times around the phase axis (the shifting is performed by a prism). Reichert & Jung were well known for this method.
Each optic had its own shifting prism adjusted to its focal length. As today, these individual prisms are no longer used in favor of a universal shifting prism; this method no longer provides acceptable results. With this method, you have the illusion of seeing more detail, yet a photograph proves that you are simply seeing shifted edges (and no real depth of field).
In comparison, the Grayfield-technique offers a variable depth of field of a quality not seen on any other light optical microscopes.
100 nanometer, focused on the upper structure.
200 nanometer, focused on the upper structure.