Contrast and Illumination
• Brightness contrast arises from different degrees of
absorption at different points in the specimen.
• Color contrast can also arise from absorption when the
degree of absorption depends on the wavelength and varies
from point to point in the specimen.
• Phase contrast arises from a shift in the phase of the light
as a result of interaction with the specimen.
• Polarization-dependent phase contrast arises when the
phase shift depends on the plane of polarization of the
incident light.
• Fluorescence contrast arises when the incident light is
absorbed and partially reemitted at a different wavelength.