Too much information about: Overheads

Overhead Projectors. What can we say about the workhorse of the AV world? Long suffering, frequently misused and always underappreciated. We'd like to rectify that with this tribute to the Overhead Projector.

We have three types of Overheads:

1. Stage
2. Portable
3. Briefcase

The Stage Overhead is the large, free standing unit with the power cord hidden in the base. The light source is in the base and shines up through the transparency and is reflected out the head lens to the screen.
Pluses: Better imaging, spare bulb, color correction.
Minuses: Heavy and cumbersome. You'll need a cart to transport. Also has a fan to cool the bulb (but it's not too noisy).

The Portable Overhead folds down and has a cover. The light source is in the head of the unit. It works by shining the light down through the transparency where it is reflected off the base back up to the head where it is focused with a lens and a mirror to bounce the image to the screen.
Pluses: Better imaging, spare bulb, lightweight, no fan.
Minuses: None that we can think of.

The Briefcase Overhead folds down into a case about the size of a briefcase. The top of the case doubles as a reflective surface and it works like the Portable Overhead.
Pluses: Portable
Minuses: No spare bulb, gets hot, the base plate must be seated properly or the image won't look right.

Troubleshooting Tips:

The Stage and Portable Overheads are pretty self-explanatory and trouble free.     However, the Briefcase Overhead needs a few tips. Since a picture is worth a thousand words...

Set-up: An overhead should be set up on the table at the front of the classroom. We do not recommend using a classroom desk, because the top is tilted back slightly and the overhead will slide off. (Really, it happens more times then you might think.)

Power Sources: When you check out your classroom before the semester starts, locate the closest power outlet to the front of the room. NOTE: not all classrooms have a power outlet at the exact center front of the room. Most overhead power cords are six feet long or LESS. Ask for an extension cord to prevent what is called "clotheslining" (where the cord is stretched off the floor like a clothesline) or having to place the projector so close to the screen the image is too small to see.

Distance from the Screen: About 6 feet or so (which makes an extension cord a necessity) to get an image large enough for those students who try to hide in the back of the room.

Angle to the Screen: Must be at right angles. If you try to set it up at any other angle, you get an image that is too wide on one side. Also, use the mirror in the head to tilt the image up and down and the focus knob to sharpen the image. Try not to tilt the image too far up or the image will "keystone" which means the top is much larger than the bottom and the image will be distorted.

A Word About Transparencies:

When creating your transparencies, remember these tips:

• Use large fonts for all your text (including information in tables and graphs)
  • We recommend a MINIMUM 24 POINT HELVETICA. 30-40 point is best.
• Avoid fonts with serifs, like Times (the font on this page is Times New Roman which looks pretty stylin' on a web site but looks awful projected on a screen) or fancy fonts like Old English or Parisian.
• Make all of your lines, dividers, charts, graphs with wide lines (2 pixels)
• Format your pages (in Page Setup) Landscape (using the width of the page, not the length)
  • This will prevent text from being cut off by audience heads or the limitations of the equipment.
• Set your margins so the page is 8" x 10" (the normal size of an overhead transparency stage is 10" x 10")

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