. The silver sunbeam : a practical and theoretical text-book on sun drawing and photographic printing. ruments are arranged somewhat in this man-ner; and the results are well known and are recommenda-tions of the cameras. The screen which corresponds tothe ground glass in the ordinary camera, is placed verticallybehind the distributing lens, and so accurately that itscenter coincides with the axis of the instrument, and alsothe distances of either edge, laterally or vertically to thecenter of the lens, are in pair respectively the same. In the portable solar camera the screen which is intended
. The silver sunbeam : a practical and theoretical text-book on sun drawing and photographic printing. ruments are arranged somewhat in this man-ner; and the results are well known and are recommenda-tions of the cameras. The screen which corresponds tothe ground glass in the ordinary camera, is placed verticallybehind the distributing lens, and so accurately that itscenter coincides with the axis of the instrument, and alsothe distances of either edge, laterally or vertically to thecenter of the lens, are in pair respectively the same. In the portable solar camera the screen which is intendedto hold the sensitized sheet, has, but comparatively speak-ing, a short space to move in; and consequently with thisinstrument it is very difficult to obtain life-size figures, be-cause an instrument that would do such work must, of ne-cessity, be very unwieldy from its size. Notwithstanding the advantage of Shives and Roettgerssolar cameras, yet their great cost has been the means ofcontracting their sale. Roettgers camera complete, witha fourteen inch lens, costs three hundred and fifty dollars;. Fig. 4. In the portable camera,of which Shives Helio-tropic, Figure 3, and Roett-gers Parallactic, Figures4 and 5, are examples,there is no reflector. Theinstrument itself is tiltedby the mechanism peculiarto each instrument, so as toreceive the direct rays ofthe sun. This is an ad-vantage over the precedinginstrument, because thereis always a considerableloss of light after reflec-tion. Another disadvan-tage of the Gale solar cam-era arises especially inwinter, when the suns al-titude is small and theangle of incidence and ofreflection is very large: thelight is thus made veryweak by such reflection. THE SOLAR CAMERA AND SOLAR ENLARGEMENTS. 447 and the price of Shives is even greater. These solar cam-eras are only adapted for the operator in large cities, whohave plenty of orders for enlarged work. The countryoperators generally find it cheaper to send their work toparties in the ci
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