What Is the Difference Between an Overhead Projector & a Data Projector?

Data projectors take their images from a digital source, such as a computer. You connect a data projector to a device using its VGA socket or composite video input port; it then projects the image through a lens onto the wall or screen. You can change settings on the data projector, including resolution, colors and brightness. By changing what is shown on the data source – for example, by switching slides in a slide show presentation – you change the projected image on the wall or screen.

Overhead projects use transparencies – clear sheets that resemble paper – to display images. You place a transparency on the surface of the projector and write or draw on it. Light shines up from the surface, through the transparency and into a mirror above the surface that redirects the light and projects it against the wall or screen, thereby showing what's on the transparency. You can also print images onto a transparency. When you need to change the projected image, you need to manually switch to a new transparency sheet.

Data projectors have many more display options than overhead projects. They display any images on your computer screen, such as text, graphics and even videos, whereas with overhead projectors you're limited to what's written on the transparency. Data projectors also tend to be smaller, lighter and more easily transportable. Because of their more compact size, they are less obtrusive than an overhead projector when placed between you and your audience, making it easier for some members to see your presentation.

If you use washable markers on the transparencies used by overhead projects, you can edit or erase what you've written during your presentation. You can also wash them clean and reuse them in later presentations. This provides flexibility when you're presenting. This freehand form of display is also simpler and faster to manage than using a mouse or touch pad with a computer to add or change content.