Modern magic lanterns; a guide to the ... - Yesterday Image

104 MODBEN MAGIO LANTEBNS.condenser. As each picture comes exactly opposite thelens the film is stopped, the lens uncapped for the pictureto faU on the screen, then capped, and the film moves onfor the next picture to be shown in the same way, thewhole cycle of operations not taking much more than a-tenth to an-eighth of a second. In some the shutter is dispensedwith, and reliance is placed upon the rapidity of themovement of the film from one picture to the next to masksuch movement from the eye, the duration of such a movingpicture being but a very smaU proportion of that of thestationary picture. It is necessary in aU of them for thefilm to be stopped while its image is thrown upon thescreen, and then moved on.Practically speaking, an instrument which will projectthe pictures can with slight modifications, or with none atall, be used for taking them, although, as a rule, a specialform of camera is employed for the purpose.The film is perforated on both sides with holes at aregular distance from each other. This perforation hasto be most perfectly done to register, as upon itthe perfection of the image when seen on the sheetdepends very largely. Teeth or pins in the apparatusengage in the perforations, and so convey the film alongits path.The standard size of film is about Ig inches wide, thedimensions of the image which is projected being 1| inchwide by ginch high. In the Lumi6re film there are twoperforations, one on each side, for each picture. In theEdison film there are four perforations on each side. Someforms of apparatus are so made that the finished film iswound up on a spool after use. Before it can be shownagain, however, it has to be rewound, as the wrong end forcommencing is outwards when it has been wound up aftergoing through the lantern. Very amusing results are sometimesobtained by putting films through the lantern backwards.There is in such case a great likelihood of damagingthe film, and it should not be resorted to without fullyunderstanding the risks which are run, since these longfilms are expensive.The apparatus for taking the picture, as we have already