Filters for Black & White Photomicrography
In black & white photography through the microscope, filters are used primarily to control contrast in the final image captured either on film or with a CCD digital camera system. Specimens that are highly differentiated with respect to colored elements from biological stains are translated into shades of gray on black & white film and will often appear to have equal brightness. When this occurs, important specimen details may be lost through a lack of contrast. Use this interactive tutorial to determine the appropriate starting point for contrast control in Black & White Photomicrography using Kodak Wratten filters.
In order to operate the tutorial, use the pull-down menu to select a stain (dye) from the provided list of common biological stains. Next, toggle between the Maximum Contrast, Medium Contrast, and Minimum Contrast radio buttons to view the recommended filters that should be added to the microscope light pathway to achieve each level of contrast. These filter suggestions are intended as a rough guide and should only be used as a starting point to fine-tune contrast filtering.
To better image specimens using black & white photomicrography, filters are usually employed to selectively absorb one or several colors, especially when using panchromatic films that have equal sensitivity to more than one stain color. Many stained biological specimens exhibit very pale colors against a bright background (using brightfield transmitted light microscopy), which will appear as light gray tones on a white background when recorded on black & white film. To enhance contrast, a color filter is added to the microscope light path that absorbs the stained specimen color, rendering it a darker gray. Contrast can be adjusted in this manner by selectively choosing filters that absorb varying amounts of the stain color.
Mortimer Abramowitz - Olympus America, Inc., Two Corporate Center Drive., Melville, New York, 11747.
Matthew J. Parry-Hill and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.
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