Photomicrography and Technical Microscopy in Its Application to Telephone Apparatus

from natural size up to magnifications of several thousand times, the degree of magnification being expressed in terms of diameters. It will be seen that the image is not always magnified but in some instances may be at a 1:1 ratio or when large subjects are being photographed, at an actual reduction in size. Such low-power work is often spoken of as gross photography but so far as the equipment and technique of treatment is concerned it is low-power work. Low-power work may be considered as treating with magnitudes from 1 to about 30 diameters. Medium-power work deals with magnifications from about 30 to about 500 diameters, and high-power work extends from 500 diameters upward. The limit of useful magnification is a much disputed question. It is sometimes contended that 1,500 diameters represents about all that is worth while, but the fact that very few pictures are published which exceed 1,500 diameters in magnification would lead to the conclusion that either the limit is from 1,000 to 1,500 or else the art has not been developed to the state where substantial gains result by going higher. This matter will be considered at greater length below. The reason that photomicrography is grouped under three classifications according to magnification, is because the apparatus used in each case is quite different and because the preparation of the subject and its treatment also differ. In fact for low-power work the microscope often may be dispensed with entirely, the lens being secured directly to the camera; in other cases, the microscope serves only as a 100 GENERAL DISCUSSION OF APPARATUS