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ADVANTAGES OF OHP. brightness. 2. Direct eye-contact. 3. Ease of use. 4. Abundance of materials. 5. Manipulable. 6. Availability of materials. 7. Self-prepared materials. 8. Advance preparation. 9. Impact on attitudes. Wharton Applied Research Center , 1981.
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More individuals followed the recommendations of presenters who used OHP than those who did not • Presenters who used OHP were perceived as better prepared , more professional , more persuasive , more credible and more interesting • Groups that used OHP more likely to reach consensus on their decisions
Cabeceiras , 1972 10. Organisation & discussion
Teachers who use the OHP tend to be more organised • Students participated more frequently in discussion
1. Not preprogrammed • effectiveness depends on the presenter • cannot display visual sequence or audio
2. Not self-instructional • Designed for large-group presentation • Not suitable to independent study • Captions & audio tracks would not be self-instructional
3. Production process required • Printed materials & nontransparent items cannot be projected immediately • Have to transfer into transparencies first • Example : magazine illustrations
4. Keystone effect • Misrepresentation of images is more common than other projection systems • Discrepancy in levels causes a distortion referred to as the ‘keystone effect’ • projector commonly placed at desktop level to facilitate the instructor’s writing on transparencies • the screen needs to be placed on a higher level for unobstructed audience sightlines