The Light of Communicatiom

The more that technology becomes the mainstay of business operations, the more that speed and distance become daily pressures in the global marketplace, the more we encounter a basic truth of human communication: nothing works better than conversing face to face. It is in our nature to depend on more than just words for our exchanges. To really feel connected, we need to see the person who is speaking. We need visual contact to get our best reading of their moods and the sincerity of their words. This human connection is critical to developing the trust and understanding that is intrinsic to a successful business relationship - even if the conversation is conducted from opposite sides of the world.

Increasingly, businesses are turning to video conferencing as a method for conducting eye to eye communication when schedules or costs make travel impractical. Universities are also using video to lengthen the reach of their programs while keeping the personal teacher-student relationship intact. As lighting designers, we see a steady increase in the demand for Video Conference Rooms and Distance Learning Classrooms. Our task is to facilitate successful human connections by lighting the participants so they can be comfortable, work easily and look natural on camera, without the use of make-up or special video effects. The lighting must attractively render their facial forms and complexions - free of distorting shadow, bright reflections and sickly pallor - while minimising glare, heat and other intrusions into their working environment. We generally find that standard television lighting concepts are appropriate, but must be modified to suit the sensibilities of the non-actor who is actually trying to conduct a conversation through the camera, not broadcast a performance.

Quite often, front lighting and top lighting for video conferencing are provided by fluorescent sources. We find that fluorescents with a correlated colour temperature of 3000 degrees and a CRI of 80 will produce acceptable skin tones. It's very important that all luminaires within the view of the camera have sources of matching colour temperature and CRI, or the video colour will never be balanced properly. Fluorescent luminaires can also generate softer, more comfortable lighting for the participants, creating an agreeable working environment in the conference room. Front lighting is directed on to faces from 45 degrees above horizontal or higher, but no higher than 60 degrees. This reduces glare and visual fatigue for the participants, while producing minimal eye-socket shadows. However, high lighting angles can produce unattractive shadowing below chins and noses. To offset the problem, we depend on bounce light from the conference table top. Horizontal work surfaces in the conference room must have a mat finish and a reflectance in excess of 30% in order to be effective.

Video conference cameras do not see as well as human eyes. They are less able to compensate for contrasting intensities of light. In order to keep the appearance of even illumination within the camera's view, we find that the maximum to minimum lighting intensity should not vary more than 1.5 to 1. Variations in excess of 3 to 1 will be noticeable, giving extra visual emphasis to the brighter area. Variations in excess of 10 to 1 will look quite uneven, like shadows. Within this limited range of contrast, however, we find that the cameras can produce a reasonable video image with as little as 300 lux on a personŐs face. However, lighting levels this low are typically only acceptable for background participants in the conference. We endeavour to light active participants, such as the students in a Distance Learning Classroom, with 450 lux to 550 lux on their faces. Principal speakers, such as the teacher, are lighted with 750 lux to 1000 lux. The intensity of the top lighting - down lighting on participant's heads and horizontal room surfaces - should be less than the front light intensity, otherwise their faces will look shadowed. Background walls must also be evenly illuminated or the conference site will look like a cavern. We find that walls must be lighted to approximately 200 lux, preferably with a soft source such as fluorescent.

Zoned dimming controls complete the video lighting system. At a minimum, top light and front lighting on principal speakers must be separately dimmable. Illumination on perimeter walls must also be on its own control zone. More complex, multi-use facilities will require several control zones, plus preset scenes and control interfaces with the audio-visual systems. However complex the room, the design intent is always the same: we must use light to smooth the path for meaningful communication.

information : www.iald.org