The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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by adjustment of the screen or lens by rack and pinion. Whilst many operators are content to use merely a white piece of paper, and to focus from the front, it will be found far pre-ferable to use the ground-glass screen and compound focusser above described. In all cases where marginal definition is defective, stops or diaphragms must be used, exactly as in field work. Having obtained a sharp focus, the next operation is placing the sensitive paper in position. The methods adopted for this are slightly different, some operators preferring to use a cap in which a piece of yellow or ruby fabric or glass is placed, so as to illuminate the surface focussed on. Others, again, cap the lens as usual, and use a ruby lantern to place the paper in position ; we prefer the former plan, because, when orange glass is used in the cap, it enables one to ascertain whether any alteration in focal sharpness of the image takes place, as this may sometimes occur from the sensitive paper buckling. Another point is the method of fastening the sensitive surface to the easel board if this be used. Of course, if the large printing frame be used, as we have suggested, there will be no difficulty about this point; but when the paper has to be affixed to a board there is a slight difficulty. One plan we have tried with success has been to have a quarter-inch groove cut in the face of the easel board along one side or the top, and in the groove a piece of stout steel or copper wire, preferably the former, is placed, and the ends of the wire are turned over the sides of the board, and passed through stout brass eyelets, and then provided with a screw thread, on which fits a milled nut. The action of this wire is merely to clip the paper in the groove, and if such a groove is placed at top and bottom of easel board, it is possible to clip the paper firmly under one groove, and then to pass it under the other, and stretch it taut, and then screw up the milled nuts. Another method is to use large-headed drawing pins at the four corners, or to use broad indiarubber bands. The advantage of using some broad surface like the head of a drawing pin is that it enables one to accurately determine whether the whites of the enlargement are pure or fogged. Surgeon-General J. L. Ranking suggested in The Amateur Photographer of November 28th, 1890, curving the paper, and gives the following directions : - " I have applied this principle to my easel in the following manner: The centre of a sheet of