Saturday, October 31st, 2020

What is a Video Projector?

A video projector takes a signal from a video source (television, DVD player, laptop, etc.) and projects it onto a screen. Much like the overhead projector common to classrooms and conference rooms of the past, early video projectors were large, cumbersome devices. Modern projectors make video portable, and are often used in home theaters and live presentations.

Different projectors use different technologies to transfer the video to the screen, but they share enough common features to make them easy to compare. All projectors need a lens to focus the light and a screen to display the image. Front projectors, like those found in most movie theaters, throw light forward, and sit in front of the screen. The throw is the distance from the projector to the screen, and will affect the screen size, so different lenses are designed for different throw lengths and screens.

A screen can be as simple as a white or gray wall, or a more complicated portable screen used in temporary settings, like meeting rooms or live events. The screen is usually flat, so as not to distort the image, and lightly colored, so as not to distort the color of the image the lens is displaying.

When purchasing a screen, make sure that it matches the aspect ratio of your projector. The aspect ratio is a mathematical measure of how the picture looks, found by dividing the image’s width by its height. For example, normal TV is referred to as having an aspect ratio of 4:3 because for every 4 inches of width, the image has 3 inches of height. Widescreen formats have just that, a wider image, like HDTV, which has a 16:9 aspect ratio, and movie theaters, which use either 2.39:1 or 1.85:1.

For even better picture quality, also pay attention to something called screen gain, which is a measure of how reflective a screen is. A more reflective screen will obviously direct more light back to the audience, which will be important when we talk about luminance. However, reflective screens can introduce hot spots, or specific areas where the screen appears lighter. Manufacturers are combating this problem with reflective gray screens, solving some reflectivity problems while allowing for deeper blacks.

Luminance, measured in lumens, is one of the most important, and expensive, measures of a portable video projector. Light in a projector is created by a lamp, and the stronger the lamp, the more lumens it will have. This translates into a brighter image, allowing it to be thrown father with ambient light becoming less of a factor. These days, basic projectors start at 700 lumens, requiring room lighting to be dimmed and projection size kept smaller. As the projector’s brightness increases, to 3,000 lumens, 4,000 lumens, and more, giant screen sizes in high light conditions are possible. Check this useful chart from Projector People to see what lumen rating will be right for your needs.

Read more about various video projection technologies:

  • CRT Video Projectors
  • LCD Video Projectors
  • DLP Video Projectors