Dealing With Ambient Light

Ambient light is light that doesn't come from the projector or display. The real problem with ambient light is its effect on contrast, and thus image quality. Here are some ways to minimize its effect on your displayed images.

  • BASIC TIPS
  • 1. Use rear-screen techniques whenever possible; rear projection is less affected by ambient light than front-screen projection.
  • 2. Use a screen material designed to absorb or deflect ambient light.
  • 3.Reduce the reflective quality of room surfaces near screen (floor, ceiling, side walls).
  • 4. Make sure lighting fixtures in the vicinity of the screen are angled to reduce light aimed directly on the screen.
  • 5. Minimize or control ambient light from the most obvious common sources: room lighting, windows and skylights, and open doors.

THE EFFECT OF AMBIENT LIGHT ON CONTRAST AT THE SCREEN

Some experts believe that contrast ratio at the screen should be at least 10:1.

Figure 1 illustrates the extreme sensitivity that contrast has to incident ambient light. Even 2 foot-candles of ambient light on the screen can drop the ratio of a front projected image to below 10:1.

DETERMINANTS OF CONTRAST RATIO

Projector contrast specifications are not the same as the actual contrast you experience viewing the screen because of the effect of ambient light at the screen. Other factors that affect actual contrast:
1. Display black level
2. Display light output (lumens)
3. Display surface (gain and reflectivity)
4. Image design (content)

CALCULATING LUMINANCE

Luminance is light reflected by or emitted from a surface. The Luminance level in footlamberts for a projected image can be calculated as follows:

Sources: Da-Lite, InfoComm.