Some Pointers on Photographing Specimens
A few simple steps will improve the aesthetic quality of your photographs. First, photograph the cut surface of the specimen. A photograph of the external surface of a specimen is seldom infor-mative. Section the specimen using a fluid sweep-ing motion to create a cut surface that is smooth and unruffled. Take the photograph before goug-ing out tissue for frozen section evaluation or tumor collection; or if these studies are urgently needed, take the tissue from an area that will not be shown in the photograph. Gently rinse blood and fluid from the surface of the specimen, and then blot the surface of the specimen dry so that fluid does not seep across the field of view.
Second, decide whether the pathology is best demonstrated in the specimen before or after it is fixed. Color is best seen when the specimen is photographed fresh, while fine structural de-tails are sometimes better appreciated in fixed specimens, which reflect less light.
Third, position the specimen so that (1) the area of interest is centered in the field of view; (2) its long axis is oriented along the long axis of the frame; and (3) the specimen fills at least 75% of the frame. For bivalved specimens, there is no need to photograph both halves of the specimen. Instead, fill the frame with a closer view of just one of the two halves. To point out a focal area of interest, use a clean and unassuming probe or pointer (not a finger).
Fourth, make sure the background is clean and free of distracters. Remember that your work is not over once the photograph is taken. Remove the specimen, and clean the background so that it is ready for the next user.
Many fresh specimens and bloody specimens tend to produce dark images on film. As a general rule, you can compensate by opening the lens by one f-stop (decrease the f-stop number). This will lighten the specimen in the final photograph.
Photographs of fixed specimens can sometimes be bleached white with little or no color informa-tion. Try taking one photograph at the normal exposure. Then take several more photographs while increasing the f-stop number in half in-crements (e.g., f-stop 16, 161/2, 22, etc.) This in-tentional closing of the lens and consequent underexposure should provide more detail in the very light areas.
Large specimens generally require at least two sets of photographs: one of the entire specimen and the other a close-up of the area of interest. The close-up photograph will demonstrate the finer details of a lesion, while the overall view will show the relationship of the lesion to the rest of the specimen.
Most normal lenses will not focus when moved very close (i.e., within 2 feet) to the specimen. A special macro lens is needed for very small specimens or for close-up photographs to show fine detail. The 105-mm macro lens is especially suitable for these purposes. It can focus to a point where the image on the negative is the same size as the specimen, while maintaining a comfortable working distance between the front of the lens and the specimen. Remember that focus is critical in close-up work. Even small specimens can have depth, so avoid focusing only on the top of the specimen by focusing on a point about one third of the way down from the top of the specimen. Also, use a small camera aperture (an f-stop of 22) for increased depth of field.
Oddly shaped specimens are a nuisance to photo-graph when they cannot be maintained in the correct position. A simple solution is modeling clay, which can be used to prop up the specimen. Mold the clay into shape, and use it as a base to hold the specimen. Before taking the picture, be sure to look through the viewfinder to make sure that the clay will not show up in the final photograph. Small fishhooks with nylon cord and an attached weight can be used to hold areas open. For example, this technique can be useful when photographing the interior of heart valves.
Under standard lighting conditions, the walls of a cavity cast shadows that obscure the base of the cavity. To circumvent this problem, place the lights as high as possible, so that they illumi-nate the depths of the cavity. This type of vertical illumination will help reduce shadows as well as light the entire cavity. A separate fiber-optic light source can also be of great help. Make sure that you are focused on the area of inter-est because depth of field can be a problem.
Side lighting is the best lighting to demonstrate surface detail or to show the three-dimensional quality of a tumor. The lower the angle of the light, the more surface relief will be seen. Shad-ows give the form shape, depth, and contrast. Be careful not to set the lights too low, as this can create harsh shadows that obscure detail.