Now You See It, Now You Don't!

TellZall's object for February is the Slide Projector.
Throughout much of the twentieth century, people used slide projectors to display images for a number of purposes. Business professionals utilized slides in presentations. Teachers presented information to their students through the use of slide projectors. Many Americans documented their vacations and special occasions with slides as well.

The main predecessor to the slide projector was a device known as a Magic Lantern. In the second half of the nineteenth century, Magic Lanterns were used to entertain and educate viewers. In addition to being the ancestor of the slide projector, the Magic Lantern was also a predecessor to moving pictures. Positive images were put onto glass plates. The Magic Lantern would then project light through the glass plate, creating the image on a wall or screen. The images were black and white, but many were then hand-colored. These lanterns originally used oil lamps for the light source, but electricity forever changed the technology by the turn of the century. In some cases, Magic Lanterns had levers that could be used to shift the slide, making it look like the image itself was actually moving.

The Eastman Kodak Company revolutionized the slide projector in the twentieth century. Eastman Kodak began producing its first slide projectors in the 1930s. Kodak introduced the Kodachrome 35mm film process. The new color slides were much less expensive to develop than the traditional lantern slides, making the technology more affordable for the average American. This new process eventually spelled the end for the older lantern slides.

Changes in vacation habits and technology made slide projectors even more popular after World War II. More American families took vacations in which they traveled to other parts of the country, and they wanted to document their experiences. In 1961, Eastman Kodak introduced the carousel projector. Rather than having to insert slides each time in a tedious process, one could put slides into the desired order in a detachable carousel. If the person owned more than one carousel, he or she could switch between carousels quickly and easily. This innovation made the slide projector even more popular and practical. Before this point, slides had to be inserted into the projector one at a time. Carousels usually hold twenty, thirty-six, eighty, or 140 slides.

Modern slide projectors use a light bulb that goes through a reflector and a special lens that concentrates the light before shining through the slide. Another lens allows the person using the projector to focus the image more clearly. The slide projector has a motor that rotates the slides and drops each one into place in front of the light source. Slides are usually made of 35mm film that is protected by a cardboard or plastic frame. Slides are positive images, meaning that the picture is exactly as it appears in reality, instead of negative images, like those of film negatives. (A negative image switches the light and dark tones.)

In November 2004, the Eastman Kodak Company manufactured its last slide projector. With the advent of advanced computer technology such as PowerPoint and the use of digital cameras, consumer interest in slide projectors had declined. Many people still collect old slides and projectors, and educational institutions still commonly utilize this older form of technology. The company donated the last projectors to be manufactured to the Smithsonian Institution and to the Eastman House. By 2004, Eastman Kodak had produced approximately thirty-five million slide projectors.