Posted on November 10, 2015 by Scott Pickus
Display Brightness vs. Ambient Light
When we consider most commercial installations, the immediate display selection that comes to mind is either an LCD flat panel or a projector. The main issue with these technologies is one of brightness; most displays we view in public spaces simply are not bright enough for the application.
High brightness LCD displays offer a major benefit compared to traditional flat panels, video walls, and projection systems.
In a typical conference room where you have 30 foot candles of ambient light, a 350-400 nit LCD is adequate, but outside of that kind of controlled environment, you may have many times that amount of ambient light falling on a display, necessitating a high brightness LCD.
According to SMPTE (Society of Motion Picture and Television Engineers), the ratio of display brightness and light from ambient sources should be a ratio of at least 5:1. This is necessary for the eye to perceive a real impression of brightness and contrast. This level of luminance is derived from the fact that SMPTE had historically indicated a target level of 50 FL for a television viewed under “normal” ambient light conditions of approximately 10 foot candles. Although displays have evolved, the rule of thumb remains valid.
This means that most displays installed in higher ambient light environments are too dim!
Recommended Brightness Levels
Many factors can affect the necessary brightness level of a display in any given environment. While ambient light and has a direct effect on a screen’s viewability, there are other considerations to take into account when recommending a display.
Ambient light, or the light present in an environment from all light sources, is the number one cause of degraded display performance in a system. Ambient light affects image contrast by reducing the range between the dark and bright portions of the image. Ambient light also reduces the appearance of color saturation and degrades color accuracy. Sunlight is the greatest contributor of ambient light for most outdoor and semi-outdoor installation locations.
Glare and reflection can also affect the viewability of a display. For example, in snowy areas the reflection of the sun off of the ground can bounce onto the display making it even more difficult to see. This problem is often seen in applications where the display is behind a surface such as glass or acrylic.
Behind Glass and Film
If the installation is behind glass, films that have been applied to the glass surface such as anti-IR/anti-UV films and tints can greatly reduce the viewability of the display.