In dark field microscopy, what is used to enhance the visibility of the specimen?

In dark field microscopy, a special condenser is utilized to enhance the visibility of the specimen. This type of microscopy is designed to observe living or unstained specimens that are typically difficult to see under standard bright field microscopy. The special condenser allows only scattered light to enter the objective lens, creating a dark background against which the specimen appears brightly illuminated. This technique is especially beneficial for studying transparent or translucent microorganisms, as it enhances contrast and detail, making it easier to observe their structures.

The other methods mentioned, such as additional light sources, colored filters, or polarizing lenses, do not specifically relate to the fundamental principle of dark field microscopy, which is primarily dependent on the use of the special condenser to create the necessary contrast by blocking direct light.