AV Technology - August 2008 - (Page 90)

avmo 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. 100 Some experts believe that contrast ratio at the screen should be at least 10:1. This graph illustrates the extreme sensitivity that contrast has to incident ambient light. Even two foot-candles of ambient light on the screen can drop the ratio of a front projected image to below 10:1. Rear Projection Front Projection 80 Contrast Ratio 60 40 20 10 0 0 1 2 3 Ambient Light in foot candles 4 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: = ANSI lumens output of projector x Screen gain Square footage of screen Sources: Da-Lite, InfoComm. www.avtechnologyonline.com 90 | AVTECHNOLOGY | august 2008 http://www.avtechnologyonline.com

Table of Contents Feed for the Digital Edition of AV Technology - August 2008

AV Technology - August 2008 Contents Precedent Corporate: The Project’s Over...Now What? Government: Generational Diversity and the Rise of the Millennials Education: DIY ISP.EDU HD Videoconferencing On a Budget Using Automatic Mic Mixers The Way I See It: The Standards Dilemma in AV Something for Everybody AV Adds the Magic to Microsoft’s Hat Trick Simple Control for Smarter Classrooms Product Review: VeEX VePAL MX100 Product Spotlight: Amps; Touchpanels New Products Ad Index AV MO: Dealing with Ambient Light

AV Technology - August 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.