Horgan's half-tone and photomechanical processes .. . the sensitive plate, whilemaintaining perfect parallelism between them, should havea micrometric adjustment. Should a prism be used with thecamera, then it must be kept at absolute right angles withthe copy-board. The plateholder should be always in perfectcondition and the camera-stand arranged to absorb all vibra-tion. It is needless to add that the half-tone screens must beperfect. THE SCREENY EFFECT IN HALF-TONES. While on the subject of the half-tone screen some ques-tions frequently asked might be answered. In the first place,the inva
Horgan's half-tone and photomechanical processes .. . the sensitive plate, whilemaintaining perfect parallelism between them, should havea micrometric adjustment. Should a prism be used with thecamera, then it must be kept at absolute right angles withthe copy-board. The plateholder should be always in perfectcondition and the camera-stand arranged to absorb all vibra-tion. It is needless to add that the half-tone screens must beperfect. THE SCREENY EFFECT IN HALF-TONES. While on the subject of the half-tone screen some ques-tions frequently asked might be answered. In the first place,the invariable alignment of the dots at angles of forty-fivedegrees to the sides of the screen is selected because it wasfound at that angle they were least objectionable. Werethey arranged, for instance, horizontally and vertically, theywould be most obvious. Would not a grain screen be morepleasing? Grain screens are in use. A most excellentexhibit of engraving through such a screen is shown in thisbook. It has been found in practice that grain screens do. FIRST of Cardinal dAmbrose, by Joseph Nicephore by Barnes-Crosby Company, Chicago, from a copy in the possessionof Mr. Albert H. Walker, New York. THE HALF-TONE PROCESS 89 not give in the highest lights and deepest shadows the deli-cate definitions or gradations of the cross-line screen. Cannot screens be made with a less mechanical pattern than crossbars? As the mechanical pattern of the screen is governedlargely by the shape of the aperture in the diaphragm, withthe ordinary half-tone screen the pattern can be varied atwill and has been so changed, but there is no great demandfor the change. Gen. Frederick W. Von Egloffsteins half-tone screensused in New York in 1868 were made with a wavy line, andthe results were not so objectionable as the straight A. Dargarvel, of London, has in use a waved-line pleasing example of work engraved with it is shown else-where. LIGHTS
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