The Art of projection and complete magic lantern ... - Yesterday Image

38handle which works the rack ; D, D, are the handles of the runnerswhich move from top to bottom, raising or lowering the supplementalshutter, as the case may be. The object of the three diaphragms maythus be described ;supposing the operator is ready to start an exhibition.The curtain slide in middle lantern is showing (diaphragmracked up) on to this a title is thrown (bottom lantern diaphragmis also up), then as the shutters are rolled down, the curtain and titlehave the illusion of being rolled up, disclosing the picture beneath(top lantern).The middle and bottom lanterns always work exactly alike, so thatif the middle lantern is occupied, the diaphragm is worked in the topand bottom lanterns. When it is required to dissolve a picture instead ofrolling it, the supplemental shutters are lifted up at the handle Z>, eachone being independent of the others. The three lanterns are left freefor dissolving effects whenever required without having toshutter from the top.LENGTHENING TUBES AND ADAPTERS.withdraw anyWhen using long locus objectives it is necessary to have long lenstubes, or adapters, to bring the lens the length of its focus, from theslide — this may be brought about by a telescopic front, a series ofadapters, or lengthening tubes, or else by a solid tube or two tubesshding into each other.Telescopic tubes have a tendency to sag, no matter how firm they maybe when new, the telescopes become loose through wear, and the weight ofthe lens will also cause these to drop in proportion—they areunsuited for a biunial or triple,altogetheras registration is impossible, the slightestpressure brought to bear on the pinion in focusing is sufficient to movethe draw tubes out of their centered position, and the larger the picturethe more perceptible this becomes. The original method of constructingthese telescopic draw tubes has been considerably improved uponof late years, and more than one patent granted for the protection of theideas. One form of droAv tubes deserves especial attention : eachdrawtube has a flange attached by which it is screwed or clamped to thenext tube,— for instance, if there is one tube with three inner draws,each draw tube is clamped to the next in such a manner as to give themthe solidity of a single draw tube. We have not given them -a practicaltrial by using them with a heavy long focus lens at the end, but froma theoretical point of view, they should fulfill all their intentions.Another method is to have three draw tubes severally fitted with a rackand pinion, each successive draw being longer and lighter than the pre-