The Optical Magic Lantern Journal (December 1899)

The Optical Magic Lantern Journal and Photographic Enlarger. 163 vertical and a horizontal line would do, but an excellent design is shown in Fig. IV. With drawing-pen, compass, and square, describe this figure on white paper or cardboard in black Indian ink lines 3; inch thick, making the circle 18 inches in diameter, and the square Fig. IV. 16% inches across. Do not forget the short diagonal line at a. Copy this in the camera, making the circle exactly 3 inches on the focusing screen, and from the negative print two lantern slides by contact. Cover glasses and binding, without masks, will complete them. , Now select two well-seasoned blocks of the sizé adopted, and fix the two templates firmly in them by means of glue and strips of cardboard, glueing in the end of the block at the same time. This must be done in such a manner as to render the glasses absolutely immovable. the corners, and to get both slides the same way about, and will thus save any vexation later on, The line a will enable us to identify | register it with the one already in use by means of the templates. A slight divergence of the square and the circle at the top and bottom may be due to the inelination of the fronts, but if they do not coincide where the horizontal line intersects, the objectives are not of the same focus, and nothing further can be done until this is remedied. This is one reason for introducing the square and circle into the : diagram; another is to show us where our picture, either square or circular, will come on the screen. If the lenses are satisfactory, change stages with the templates. Do the lines | agree now? If so, the workmanship is highly creditable, as the enlargement of the slide | would not only magnify the error, but changing ‘ the stages would double it, _ circle of 6 feet diameter the Thus, if with a error is a ! quarter of an inch, the discrepancy in the caused by the twisting of one of the templates, © revealing a slight want of squareness in the diagram. See that the measurements from the horizontal line to the edge and from the vertical line to the end are slightly in excess of what is required, and, with the plane, which must | always be kept sharp and finely set, shoot off ' the bottom edge until it is parallel with the horizontal line at a distance of 2 or 21 inches, as the case may be; then square off the end until it is 84 inches from the vertical line. Do this to one frame only. Next, light up one lantern, place this slide on the runner and against the stop, and focus sharply on a wall or ° small screen. Mark the position of the vertical and horizontal lines very carefully by pencil marks or rows of pins, remove this slide and shoot the frame of its fellow until the lines projected by it from the same stage agree with the marks. Great care must be used in doing this, even the temperature of the glasses should correspond, and the slides may next be tested, as follows:—Light up another lantern, and templates would be } + 2 + 24 = ;4,. inch. It is quite possible to make templates correct to <csc inch by the method described. With our templates satisfactory, we may now proceed to mount and register all our slides and effects. First of all, insert the masks selected, taking care they are all the same way up, and square to the objects in the view. All pictures are not square to the edge of the glass, and it is most unsightly to see a vertical object made to look out of perpendicular by a carelessly placed mask. In the case of effects, bear in mind that the edges must register as well as the details of the picture. Secure the slides firmly in frames, bearing in mind, if card has to be used, that it is slightly compressible. Then register the lantern carefully by means of the templates, and commence shooting the frames to bring the pictures into exact coincidence. Make frequent comparisons with one of the templates, so as to keep the picture central and upright. In the case of effects, register the whole series to the first slide of that series, so that an addition of minute errors may not lead to a palpable discrepancy between, say, No. land No. 7. Register the first of each lecture set to a template, so that a slide may be introduced into another set without disagreement of margin, and, with this system carried out, any slide or effect will coincide with all other slides upon the screen. Remember, above all things, that objects are reversed, and if a slide is too high, planing the frame will only make it higher, and so on. Thus, with perseverance and intelligence, the acme of perfection in registration may be attained.