Brian, thank you for your identification. Your knowledge on the topic is impressive. I prefer to shoot video for that reason. It can provide much more information than stills.
Rogelio, Charles, Litonotus thank you.
Charles, with certain objectives the DIC prisms do not make a good match. I try to hid this by adding a gradient to the opposite side in post.
Reichert Diastar infinity microscope with 1.40 NA DIC condenser
I have 10, 20, 40 reichert plan achromats and a 100x reichert plan fluor 1.30 that give a nice even background DIC image, a 40 reichert neoplan that shows a strong gradient, nikon 20, 40, 60, 100 planapos(noninfinity) that give mixed results. The 60 is a great match. Even when using 30mm ultrawide eyepieces the background is relatively even. The 40 is not a good combination but it gives acceptable DIC if I stop down the condenser. here's an example. The first 2 scenes are done with the nikon 40x plan apo.
http://www.youtube.com/watch?v=eeuONqXD ... ature=plcp