=Putty up all Cracks= between the boards in the top and front, to make the box light-tight; then
=Paint the Inside of the Box= and the cover boards with lamp-black thinned with turpentine, so there will be no reflections other than those produced by the lamp reflectors and the picture.
[Ill.u.s.tration: FIGS. 343 and 344.--Details of Lens Mounting.]
[Ill.u.s.tration: FIG. 345.--View of Back of Reflectoscope.]
[Ill.u.s.tration: FIG. 346.--Detail of Post Card Holder.]
=Nail the Back Boards in Place=, leaving an opening about 7 inches square directly opposite the lens. Cut a piece of board to fit this opening (_E_, Fig. 345) for
=The Picture Holder=, and hinge it in place. A frame for post cards to slide in should be fastened to the picture holder, as shown in Fig. 346.
First nail strips _F_ to board _E_, then tack strips _G_ to them so their edges project over strips _F_. A little wooden b.u.t.ton (_H_, Fig.
345) will fasten the holder board shut while each picture is being projected.
=The Lens Reverses Pictures= in projecting them, and in order to have them projected right-side up on the screen it is necessary to slip them into the holder frame upside down.
=Adjustments.= After you have built your reflectoscope, you may find it does not throw sharply-defined images upon your projection screen. In that case you must readjust the focus of the lens, the curve of the lamp reflectors, and the distance between the lens and the projection screen, until the best possible results are obtained. Inasmuch as the positions will vary with different lenses, it is impossible for me to give any hard and fast measurements. You will have to determine the distances yourself.
The stronger the light, the brighter the projected image will be; therefore, use the strongest light you can get, and place the lantern not more than five feet away from the screen.
Unless you use an anastigmat lens such as the better grade of cameras are fitted with, you will discover that the corners of pictures are indistinct when you have brought the centers to a sharp focus. This indistinctness can be corrected to a great extent by blocking out the holder to curve the post cards and other pictures so that the ends are closer to the lens than the center is.