OIL Darkfield Condenser for i4 MicroscopeDarkfield microscopy uses refracted light to make live, unstained specimens appear with bright contrast against a dark background. By blocking the center of the brightfield of light and not allowing direct rays to enter the objective, only the outer oblique rays of light strike the specimen. Put 2 drops of immersion oil onto the top of the OIL condenser and raise it until the oil contacts the underside of the slide for the sharpest darkfield