OHP Mechanism Large Box Bright lamp, fan Large lens Long arm Mirrors Lenses Transparencies
OHP Focal-length adjustment FOCUS Adjustment wheel Distorted images Very hot lamp, 750 watt Less than 100 hours, needs cooling Different from LCD
OHP History Us Army 1945 WWII In schools and business 50s, 60s 1957 Federal Aid to Education program publicized OHP
OHP Use in Education Bigger views of sentences, and images Revising classes (rolls) Transparency sets (units, grammar, conversations) Gradual show-up of info Graphics and language, no need for darkness Hand or computer generated transparencies
OHP New developments The emergence of LCD OHP Part of classroom computer projection system 1990s A liquid-crystal panel mounted in a plastic frame was placed on top of the overheard projector and connected to the video output of the computer
OHP Decline in use Less bright then a anew video projector or data show Electricity consuming Less flexible than a computer Only visual, and mainly still images Needs transparencies 2000s, fading out
Tips On using OHP Big clear fonts New clean transparencies A 45-degree angle to the audience is the most effective location for an overhead projector and screen. Colored transparencies, colored pens, printing, or pasting Adjust transparencies right; head to head, readable
Tips on using HOP Turn OHP off if you do not need it while speaking Hide parts of the transparency “gradual show up” use a pointer (a pen or a laser pointer) Do not stick to the screen keep to the device, keep it to your right. Do not hide the light with your body.
Tips on using OHP Turn it off when changing Transparencies Prepare your transparencies and number them, do not miss them up. What do you think of this use?
Model of using OHP view this scene on using OHP: List weaknesses And strengths
Slide Projector components a fan-cooled electric light bulb a reflector and "condensing" lens to direct the light to the slide, a holder for the slide and a focusing lens. A flat piece of heat absorbing glass is often placed in the light path between the condensing lens and the slide
History common in the 1950s and 1960s as a form of entertainment; family members and friends would gather to view slideshows Still films were common Enlarged reversed image (placed up side down) Positive film, not negative. Kodak was famous manufacturer, in 2004 stopped production
Types of slide projectors Old double Decker Takes no more than two slides No voice
types A carousel slide projector. Holds a pack of slides (25, 36, 50, 80)
types The tray projector A big number of slides in a tray (magazine)
types The tray projector with synchronized voice Can project on its inner screen and on an outer screen Uses a remote controller
Slide projector decline the slide cube projection system ultimately faded out because of its serious drawbacks, including the inability to back up more than one slide, the fragility of the cubes, and more than anything, the unreliability of the system a strong tendency to jam
Tips on using the slide projector Use a special camera for making slides Not only images, can be graphics or charts Prepare an outline for talk Prepare a good program for the voice enable type Rehearse alone, and be prepared for jams Do not depend on the technician.
Episcope Used for projecting flat opaque images, like postcards, prints, photographs, pages of books, but also three-dimensional objects like coins, insects and leaves, on to a screen An epidiascope is a projector for showing both transparent slides and opaque objects. This combination of functions made the epidiascope the ideal projector for schools.
Episcope use Used in education enlarging images, and 3d objects Easy to handle because no need to produce materials Used widely by painters and designers for enlarging images to draw the details. In the early and middle parts of the 20th century, low-cost opaque projectors were produced and marketed as toys for children.
Mechanism The photo or object is place up side down, Reflected on a couple of mirror and Projected on an outer screen. Because they must project the reflected light, opaque projectors require brighter bulbs and larger lenses than overhead projectors, and need total darkness