First steps in photo-micrography / [F. Martin Duncan].

  • F. Martin Duncan
Date:
1902
Catalogue details

Licence: In copyright

Credit: First steps in photo-micrography / [F. Martin Duncan]. Source: Wellcome Collection.

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    upon the lens, stop, and plate used; on the actinic power of the light employed, and the subject to he photographed. As some sort of guide, we will suppose that we wish to photograph part of a spray of lily of the valleAr, with a magnification of about four to six diameters, by reflected daylight. With a fairly strong north light, a rectilinear lens working at y/16, and an Edward’s hacked instantaneous isochromatic plate, an exposure of forty to forty-five seconds should he ample. It is better to slightly over than under ex- j)ose the plate, if not quite certain of the exact amount of exposure required. Suppose we wish to obtain a photograph, by transmitted light, of a small insect mounted in Canada balsam, and magnified ten or twelve diameters. If the object is fairly transparent, the light (say a good round-wicked paraffin lamp) properly centred, and the plate used an Edwards’ instantaneous isochromatic, an exposure of eighteen to twenty or perhaps twenty-five seconds, should produce a satisfactory negative, full of detail and gradation.
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