Solution: This probably results from having the field diaphragm and/or the aperture iris diaphragm of the condenser off center. Also check the substage condenser aperture diaphragm to ensure it is opened to a value between 65 and 80 percent of the objective rear aperture diameter.Īlthough my exposures and color fidelity appear fine, the photomicrographs show an uneven intensity from one side to another. Do not use a photoeyepiece having a magnification factor less than 2.0, because these are meant for video imaging, not for photomicrography with film cameras. Make sure that, in setting up Köhler illumination, the field diaphragm has been focused on the already focused specimen, centered, and opened beyond the outline of the film frame. Solution: This is probably the result of failing to open the field diaphragm (in the base of the microscope at the light port) sufficiently to clear the outline of the film frame as shown in the frame finder eyepiece or focusing telescope. My image quality appears fine, but there are dark areas vignetting the corners of the photomicrographs. Likewise, color balance errors that result in yellowish highlights and shadows can be corrected with the use of a CC blue filter. For example, a green cast is removed by the use of a CC magenta filter, with the density of the filter being dependent upon the intensity of the green cast. Once the compensating filter color has been determined, the appropriate density must be approximated by means of test exposures. To use the color triangle, follow the arrows from vertex to opposite side or from side to opposite vertex. Consult the color compensating triangle, illustrated in Figure 1, for selection of the correct color of the compensating filter. Solution: Make sure you have set the reciprocity setting for the film being used and try one of the Kodak Wratten CC filters (complementary to the undesired color cast) in the light path. My exposures are several seconds long and resulting photomicrographs show an overall color cast (either magenta, blue, yellow, green, cyan, or red). Make certain you are using an Olympus LBD, Nikon NCB or Kodak 80A conversion filter in the light path to boost the color temperature to a value of 5500 K. Solution: The light source color temperature is too low for the film emulsion. I am using outdoor/daylight film and the exposures are below 1/2 second, however my color micrographs are very yellow overall (both the background and the specimen). Make certain that you do not inadvertently have the Olympus LBD or the Kodak 80A filter in the light path. Solution: The color temperature of the light source is very high and not suited for the film emulsion. I am using indoor/tungsten films and the exposures are below 1/2 second, but my photomicrographs are very blue overall (background and specimen). The Olympus equivalent of this filter is the LBD and the Nikon equivalent is NCB. If you are using daylight-balanced film, make certain a Kodak 80A (or equivalent) color-balancing filter is in place. If the background tint is very subtle, a Kodak Wratten color compensating filter (10CCB or 20CCB) may be sufficient to remove the yellowish cast. Try using one of the Kodak 82 series Wratten filters to raise the color temperature. Solution: The illumination color temperature is probably too low, an indication that you may be using daylight-balanced color film with a tungsten light source. If the blue background is very subtle, a low-density color compensating filter (CC10Y to CC20Y) may be sufficient to correct the problem.Įxposures are shorter than 1/2 second, but the clear background of the photomicrograph appears yellowish instead of white. Try using one of the Kodak 81 series Wratten filters to reduce the color temperature. This is one of the most common errors experienced with color photomicrography. Solution: The color temperature of the light source is probably too high for the film emulsion. Exposures in brightfield are shorter than 1/2 second, but theĬlear background of the photomicrograph appears bluish instead of white.
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