Choosing the right ... Overhead Projector (OHP)At first glance, it might appear there's nothing at all to buying an OHP.
After all, they're just a box with a light inside it !Sure it' s easy to buy the cheapest ... but ... ask yourself the question ... is it going to do the job that you and your colleagues really need it to do !!
Types : There are 2 basic types of OHP. Transmissive and Reflective.Transmissive projectors have the light source (bulb) in the base of the machine. The light is projected up through the glass plate (called the 'stage'), through a magnifying lens in the projectors head ... and then onto a projection screen.Lens : There are 3 types of lenses. Singlet, doublet and triplet.
The 3M 1700 Series and 9000 Series are Transmissive.Reflective projectors have their light source in the head of the projector. The light shines down onto the stage and then reflect back up through the lens and onto the projection screen.
Both types have their own advantages.Transmissive are usually brighter and the images are typically sharper. But they tend to be larger and heavier. If you intend to use a LCD Panel with the Projector, Transmissive projectors are a must.
Reflective projectors (Series 2000) are ideal if you want portability and will only be using transparency film. They are a good choice for mobile presenters as they are lighter in weight and smaller.Singlet is the most basic lens, triplet the most powerful. Price obviously increases depending on the lens used. As the lens quality increases, so does the sharpness of the image. Also, the lens type affects the projectors focal length (how close or far from the projection screen ... the projector will focus).Brightness : A projectors brigtness is measure in lumens.Levels range from around 1,700 to 11,000 depending on the model. Black and white images in a small room need only a low lumen level. If you have colour transparencies it's advisable to select a projector with more lumens. If you are using a projector with an LCD panel, at least 4,000 lumens is recommended.Lamps : Lamps area crucial part of projectors.The lamp you select will affect the purchase price but may well save you money in the longer run. Some projectors offer a high/low switch which can almost double the life of the lamp. A lampchanger allows the presenter to switch over to another lamp if one fails during the presentation.Like to see ... More Tips ? Click Here !
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