Pilot Study: Measurement of Room Illuminance to Assess Automatic Brightness Control in Televisions

TitlePilot Study: Measurement of Room Illuminance to Assess Automatic Brightness Control in Televisions
Publication TypeConference Proceedings
Year of Publication2012
AuthorsGreenblatt, Jeffery, Mia Forbes Pirie, Louis-Benoit Desroches, Sally M. Donovan, Clancy Donnelly, Craig Billingsley, and Chris Calwell
Date PublishedAugust 12
Conference LocationBerkeley

Automatic brightness control (ABC) is an increasingly common feature found in newtelevisions (TVs) and computer monitors. ABC is intended to adjust TV screen brightness(luminance) according to the ambient light level (room illuminance). When implementedcorrectly, this can both reduce energy consumption and improve viewing quality. The currentENERGY STAR test procedure provides for a more favorable energy use rating for TVs withABC, by measuring power consumption at two light levels (0 and 300 lux) and reporting aweighted-average energy use. However, this and other studies suggest that these levels are notrepresentative of actual TV viewing conditions.As there were currently only limited data available concerning room illuminance, weundertook a small pilot study in 2011 to begin to answer two key questions: 1. To what extent doroom illuminance levels vary depending on the location of measurement (e.g., center of theroom, on the couch, or at the TV)? 2. What room illuminance conditions are prevalent whenpeople watch TV?We measured room illuminance in the homes of nine volunteers in California andColorado to begin addressing the above two questions. Although the study had the usualdrawbacks of a pilot (limited sample size, time duration, etc.), it has, nonetheless, yielded usefulresults. The study shows definitively that there is large variability between measurements madeat different locations in the room and, therefore, that location of room illuminance measurementsis critical. Moreover, the majority (over 75%) of TV viewing occurred at illuminance levels ofless than 50 lux (though measurements of up to several hundred lux were also recorded), a resultthat was consistent with subsequent larger-scale studies. This type of information can helpdetermine how ABC-enabled TVs should be tested to best represent actual viewing conditions.


Conference Proceedings, 2012 ACEEE Summer Study on Energy Efficiency in Buildings