The Educational screen (c1922-c1956])

November, 1930 267 only a few special pictures in the class-room or in the home. One slide can be showing while the other is changed. The small slide may be left in the projector for a few moments or for half an hour without any danger of overheating. A positive picture l}i by 1^4 inches is the largest size which can be used in this Leica projector, although a slightly longer picture can be used, if it is made narrower. By removing the film-slide mat in the Leica projector, the full aperture of the lens is utilized, and consequently a slightly larger positive can be used. In making the l^^xlj^-inch positives, process-cutfilm can be used instead of safety motion-picture film. Any negative larger than the Leica lxl>^-inch size can be reduced in the enlarging camera and projected on the film or direct on the quarter-size lanternslide plate. This process permits the use of any grade or make of lantern-slide, cut-film, or motionpicture film stock. I have produced some of my clearest filmslides by reduction from 5x7 and 8x10 negatives in the enlarging camera. If the enlarging apparatus is not available, good results may be obtained by using the Leica camera and the special reproduction stand for copying photographs or small objects. The negatives can then be converted into positives by direct contact printing. When the positive is made on the lantern-slide emulsion, it is necessary to either varnish the slide or place a cleared piece of cutfilm over the picture surface for protection. Film-slide rolls as well as individual film-slides can be projected in the standard 3% x 4inch Baloptican projector by using regular attachments made for the purpose. The Bausch & Lomb Optical Company makes an excellent double-frame projector attachment which is quickly interchangeable with the regular lens-mount used for lantern-slide projections. An added advantage with this double-frame attachment is that the full power of the 500-watt light creates a brilliant image when it is necessary to project the film-slides longer distances. There is a special groove in this Baloptican film-slide attachment for inserting the small individual film-slides. The regular film-strips are easily passed through the projector by a turn knob. Another method of projecting Figure 3 Willard D. Morgan This picture shows the metal holder for the small individual film-slides, when they are to be projected in the standard-size Baloptican lantern. The holder shown in this picture was made for the Los Angeles County Visual Education Department for use in their Baloptican to demonstrate the possibilities of the smaller individual film-slides in the county schools. A comparison is also made in this picture to show the relative si::es of the standard and smaller slides. This slide holder can be made out of sheet metal or cardboard. By having two of these holders in the slide-carrier it is possible to project the .^niall film-slides in the same way that the larger 354 x 4-inch .■itides are shown. the individual film-slides is by using special holders inserted in the regular Baloptican slide carrier to hold the smaller slides. Such holders are easily made out of sheet metal or even heavy cardboard. The special film-slide holder, as shown in the accompanying illustration, was made for the Los Angeles County Visual Education Department to use in their Baloptican projector in demonstrating the possibilities of the individual film-slide in the educational program. I n this same illustration a comparison has been made to show the relative sizes of the standard and smaller slides, all of which may be used in the same lantern-slide projector. Additional Advantages of the Single Film-Slide An important feature of this individual film-slide is that vertical as well as horizontal slides may be placed in the carrier and projected without turning the front lens-mount around, as is the case when the long film-strips are used with vertical and horizontal pictures. In this way it is not necessary to make the vertical pictures smaller in order to squeeze them into a fixed space, as in the singleframe slides, which are 1 by ^-inches in size and cannot be turned during projection. In mounting the positives on glass for the Leica double-frame projector, the exact position for centering the picture can be obtained by making a test slide first and using it as a standard for the others. In order to test the breakability of these small individual film-slides mounted on glass, I took a handful of them and tossed them across a fifteen-foot room, where they landed on a hardwood floor. Strange as it may seem, not one slide broke. Even if the glass mount did crack, it would be a simple matter to replace with a new glass if the positive is on the film part of the slide. The outcome from a similar test with the