The 35mm or 2x2" slide has become the standard visual aid for scientific presentations. It has many advantages and virtually any material can be placed on a slide. other aids such as "overhead transparencies" or computer generated overhead images may be used, but are sometimes difficult to see from a long distance. Problems with slides generally fall into three categories: (a) reversal, (b) out-of-order, and (c) illegible. The first two can be prevented by simple care, use of standardized equipment (bring your slides already in a "carousel" tray if possible), and a pre-check by the speaker and the session moderator. The third is much more serious and difficult to conquer, but it can be mastered.

Good slides clarify the message, stimulate interest, and help the speaker keep on track. They merit the same care in preparation as the commentary. Slides that cannot be read when projected lessen the impact and effectiveness of the presentation.

Most errors in slide-making stem from the mistaken assumption that legibility in one form assures legibility in another. A person ordinarily reads printed material at a distance of 12 to 14 inches (304 -356 mm). But frequently at a slide presentation the image projected is only 4x6 feet (1.2x 1.8m): the rear seats are 70 feet (21.3m) from the screen! Reading the text of a 4 foot high image at 70 feet is like reading this page reduced to 33x44 millimeters. None of it would be legible because of the small size of the original characters.

Illustrations in textbooks and reports are usually drawn carefully and labeled in detail. Copying such illustrations in slide form may be inadequate for the screen. Line widths must be increased. Captions must be reduced in number, simplified, and increased in size. If you reduce a blueprint to slide form and project it, the screen image will be illegible. Lines will be too faint, lettering will be too small, and the narrator will usually lose the audience while trying to explain in words what the audience should be seeing. A thick-line tracing of essentials, made with crayon, felt-tip pen, etc., or a simplified version is preferable.

Use a template measuring 4 1/2 inches by 5 3/16 inches typing copy for slides: 8 double-spaced lines (maximum) and 40 elite (or pica) characters wide (maximum).

Upper and lowercase elite type will be legible up to 40 feet (12.2m) from the projected image 5 feet high (1.5m): pica type to about 60 feet (18.3m). The use of uppercase letters only will extend the legibility distance somewhat. Keep captions, lines and other markings (added to illustrations from which slides will be made) within the rectangle. Use the template as a guide for setting up your camera: the viewfinder should include about 1/8 inch (3mm) outside the template area on all slides You may find it helpful to trace the template on onionskin or clear plastic material that can be used to check copy area and to align the camera. Be sure to remove the tracing before photographing the copy.

Computer Generated Materials.

Most slides and overheads containing data or text are produced on personal computers. Arguably, the most popular graphics and data software are Harvard Graphics, PowerPoint, Excel, and ClarisWorks. There are sources for these software at USC Aiken and you should make every effort to avail yourself of these resources.

Once the slides with data or figures are on the computer screen, save the images to disk and take the disk to a photo shop for quickly produced photographic 2x2" slides.

• Use 35mm, 2x2 inch color slide film. Slides are effective, easy to make, and inexpensive. Color film is also convenient for making slides from black-and-white copy.

• On the computer, use a software package such as "Power Point" or others. Select a colored background: it is better than black or white. If you are photographing a data sheet using a 35mm camera, put a green, blue, dark yellow, etc. filter over the lens when photographing a black-on-white copy.

• Limit each slide to one main idea.

• Use a slide series for progressive disclosure.

• Limit each slide; include no more information than you will discuss.

• Leave space, at least the height of a capital letter, between lines.

• Include titles to supplement, not duplicate, slide data.

• Use several simple slides rather than one complicated one, especially if you must discuss a subject at length.

• Use duplicates if you need to refer to the same slide at several different times in your talk. It is impractical for you or the projectionist to search for and reshow a slide.

• Plan your slides for a good visual pace in your presentation. Don't leave a slide on the screen after discussing its subject.

• Thumb-spot all slides in the lower left corner where the slide reads correctly for hand viewing. Add sequence numbers.

• If you have to say "Some of you may not be able to see this, but...", DON'T SHOW THAT SLIDE! If the slide is not legible from every point in the auditorium, it is useless. Never take an illustration from a thesis or printed paper: the print is usually too small and there will be too much unnecessary detail.

• Rehearse your slide presentation several times so that you will be familiar with the sequence and timing of the slides.

• On your trip, carry your slides, in the tray if possible, with you. Don't trust them to your baggage if it is checked through.

• Give your slides to the projectionist before the session, when you'll have time to discuss any special instructions with him. If you wait until just before you talk, he may be busy with the previous speaker's slides.

• Use the slides to supplement and support your oral presentation, not simply to repeat what you are saying.

• Request a laser pointer, if needed. These electronic pointers permit quick, precise accuracy.

• Project your slides from 50-75 feet in a partially darkened room, and make sure you can read everything on them from at least the projection distance, preferably further.

• Each slide should be marked for numbered sequence to assure proper order in carousel for projection: and with your name to assist retrieval. Feel free to bring your slides properly marked and arranged in your own carousel tray. Be sure the tray has a lid lock firmly in place. Make a trial run well in advance of the meeting to make sure each slide is in proper sequence, right side up, and facing properly (not backwards). There will not be time to rearrange slides during your scheduled appearance.

• Plan on no more than 15 slides, preferably fewer, for a 15-20 minute presentation.