The material that you project determines what level of brightness you'll need. For example, clear transparencies require a lower level of brightness than color transparencies. A projector's brightness, which is measured in lumens, is a factor if you plan to use an LCD projection panel. Because it sits atop the overhead projector, an LCD panel requires the brightest light source available. The more lumens a projector has, the brighter the image.
Some projectors offer dual lumen settings to accommodate various brightness levels.
Lamp changer . Rotating head . This adjusts an image so it can be shown at a variety of meeting venues. It's especially effective with the use of LCD panels. Cooling system .