Examples of Phase Contrast
Cheek epithelial cell
Alignment of the Phase Annulus with the objective phase plate is critical. Here the two rings are centered, but the incorrect Phase Annulus was chosen. The ring of light from the Phase annulus (B) must be the same optical diameter as the Phase plate (A).

Lighter light ring is a reflection.

Biofilm as visualized in Phase Contrast (200x).
Note the "Phase Halo" effect.
Alignment of the Phase Annulus and Phase plate.