This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1920 edition. Excerpt: ... photo-micrography. Good work may be done, however, with the petroleum lamp. It may be well to recall the statement made in the ...Read MoreThis historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1920 edition. Excerpt: ... photo-micrography. Good work may be done, however, with the petroleum lamp. It may be well to recall the statement made in the beginning, that Fig. 137. ProJection Ocular Is Section. (About natural Size). / The upper or eye end of the ocular; it is composed of two convex and one concave lens and serves to project the real image formed by the objective and field lens at d upon the screen or photo graphic plate. It is movable to permit of focusing at different screen distances. 2 Field lens of the projection ocular. d Diaphragm where the real image is formed. the specimen to be photographed must be of special excellence for all powers. No one will doubt the truth of the statement who undertakes to make photo-micrographs at a magnification of 500 to 2000 diameters. If one has a complete outfit with electric arc light the time required for photographing objects is much reduced, i.e., ranging from 1 to 20 seconds even with the color screen. As the light is so intense with the arc light it is necessary to soften it greatly for focusing. Several thicknesses of ground-glass placed between the lamp and the microscope will answer. These are removed before taking the negative. It is well also to have a water bath on the optical bench to absorb the radiant heat. This should be in position constantly (see fig. m, 131). 367. Use of oculars in photo-micrography.--There is much diversity of opinion whether or not the ordinary oculars used for observation should be used in photographing. Excellent results have been obtained with them and also without them. When an ocular is used the eye-lens serves to project a real image of the objective, not to act as a magnifier with the eye as an ordinary observation; therefore for the best results in photography this...Read Less
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