Education Projectors Buyer's Guide
Aspect ratio defines the relationship between the width and the height of an image. For example, if your old television screen was 40 inches wide and 30 inches high it would have an aspect ratio of 40/30, which is equivalent to 4/3 and commonly shown as 4:3. So the aspect ratio defines the relationship of the width and height of the display, but not its size. It gives a sense of how square or rectangular the image is.
Have you ever borrowed a projector for your class and seen black bars on either the top and bottom or sides of the projected image? There are two ways this can happen: 1) if the projector has a different aspect ratio than the screen, or 2) if the material you're projecting has a different aspect ratio than the projector.
Nearly all projectors today allow you to electronically stretch or shrink an image to fill all or most of the screen; however, there is always some loss of detail when doing this and it is more noticeable on text than video. The finer the text the more evident the problem.
If you intend to use HDTV, its aspect ratio is 16:9 meaning it is 16 units wide for every nine units high. This is similar to what you might find at a movie theater or even your home television. So 16:9 is proportionally wider for a more panoramic experience while the 4:3 of regular TV looks almost square by comparison. There are many aspect ratios in both the computer and video worlds. The emerging standard for many laptop computers is 16:10, which is close enough to 16:9 to hardly notice the difference.
In choosing your projector, you need to determine which aspect ratio is most prevalent in the multimedia curriculum you’ve developed for your students and, perhaps more importantly, which way are you headed in the future. Consider the DVDs, tapes, computers, and televisions you already have to help you decide which aspect ratio to choose. If standard definition is the bulk of your content and you are not transitioning to high definition, then a 4:3 projector may be best. If you have high definition content or a mix of standard definition and high definition content, then 16:9 may be best.