Phase microscopy techniques are particularly useful with specimens that are thin and scattered in the field of view. Such halos are optical artifacts, which sometimes obscure the boundaries of details. The phase annuli do limit the working numerical aperture of the optical system to a certain degree, thus reducing resolution. Phase contrast does not work well with thick specimens because of shifts in phase occur from areas slightly below or slightly above the plane that is in focus. Such phase shifts confuse the image and distort image detail.
Phase images appear gray if white light is used and green if a green filter is used.
In the past, many microscopists restricted their film to black and white when performing photomicrography on phase specimens. Today, many color films reproduce black, white, and grayscales very effectively, especially the tungsten-balanced transparency films from Fuji, Kodak, and Agfa. Phase microscopy is another exemplification of how the manipulation of light at the substage condenser lower lens level and at the objective rear focal plane level has significant effect upon the image that is observed through the eyepiece. Authors Mortimer Abramowitz - Olympus America, Inc., Two Corporate Center Drive., Melville, New York, 11747. All Rights Reserved .