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Tips for using Overhead Projectors
As technology goes, the overhead projector (OHP) is fairly old, dating from 1930s. It is easy to use, flexible, and affordable.
Special advantages
- Focuses students' attention
- Can be used with lights on
- Can be used effectively in larger classrooms where blackboard is not large enough to be seen; variable image size
- Teacher faces the classroom so maintains intimate contact
- Increases student-teacher interact, questions and answers, etc.
- Teacher controls speed of presentation
- Inexpensive to use, no special equipment aside from viewing screen
- Materials can be prepared ahead of time
- Students can use it with minimal training
- Can be used with clear transparencies or opaque objects (cut-outs) .Can show magnetic fields, or use containers with colored water
- Can use overlays to enhance transparency image
Care
Most equipment comes with a plastic cover, good for keeping dust off.
The most vulnerable part is the lamp, especially to humidity.
Don't touch lamp with bare hands.
Don't touch lamp when hot; allow equipment to cool down before moving
To clean lens, use an anti-static cloth or soft brush, like a photo lens brush
Don't carry the OHP by its pillar or post as it can pull the pillar and projection head out of alignment.
Projection tips
Consider your lecture style, do you prefer to stand or sit?
Make sure everyone in your audience can see the projected image.
If the projector is set up 2-3 meters (5-8 feet) from viewing screen, the resulting image will be about 2 meters by 2 meters (60 inches by 60)
For best results, use an opaque white matte screen (no-glare reflection). It's best if the screen is 2 meters or more in size. It can be rigid or cloth. A rigid screen can be propped on a chalk tray attached to a black board.
For best results, keep the screen bottom about 2 meters (5 five) from the floor to ensure the back audience can see.
For best results, slant the screen forward slightly so it meets at a 90 degree angle with the projected image light beam. In not, then a keystone effect results where the projected image is taller on top or on the sides; in other words, the projected image is a parallelogram, not a square.
Place screen so there is no direct sunlight upon it.
One general rule about projected image size: judge the distance between screen and farthest viewer, divide by six and use this number to figure image width.
A brownish border around picture is indication image is not in focus.
Some people switch the projector on and off to shift the focus of the audience from the image back to the speaker. This also saves the lamp. This is a matter of personal presentation style.
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