Sparks Electrical News February 2019

LIGHTING

21

HOW GOOD LIGHTING CAN HELP WITH GLARE

W hatever the application, a very basic principle always applies: a lighting installation needs to be visually comfortable for its users. But as Philips notes, some applications are especially demand- ing from a visual comfort perspective. Take offices, for ex- ample. Due to the intense concentration that’s required of office workers, and to the fact that they typically do their work in front of computer screens, providing the highest level of visual comfort is crucial. But what do we mean by visual comfort and how can we achieve it? Visual discomfort is associated with both psychologi- cal and physiological effects. It involves eye fatigue (which can manifest itself in sore, red, and itchy eyes) and can lead to headaches and to neck and shoulder pain. It can also have a negative impact on performance, mood, and motivation, and boost the amount of sick leave em- ployees take. Visual discomfort can have various root causes, alone or in combination. Too little or too much illu- minance can cause it, as can strong illuminance con- trasts or distracting light patterns. Flicker or strobo- scopic effects (temporal lighting artefacts, as they’re technically known) can cause it. And so can glare… Glare is a phenomenon caused by extremely bright light sources or by strong brightness contrasts in the visual field. (Brightness, for its part, is the per- ceptual sensation caused by a luminous source or reflecting surface). Glare sources include windows, glossy magazine pages, computer screens, or incor- rectly designed and installed artificial lighting. The impact of glare is linked to the luminance of a source or surface – that is, to its light intensity in a given direction per surface area, measured in cande- la per square metre. But it also depends on other pa- rameters, like luminance contrast in the visual field; and on the viewer’s age, iris colour, and individual sensitivity to light. Disability glare vs. discomfort glare Excessive brightness can have a serious direct im- pact on visibility and on our ability to perceive ob- jects. When brightness has such an effect on us, it’s subjecting us to disability glare. A typical example of high-level disability glare is when, driving on the highway at night, you’re dangerously blinded by the bright headlights of the car coming at you from the opposite direction. Inside a building, bright sunlight entering through a window can cause disability glare. Discomfort glare, on the other hand, occurs when people don’t feel comfortable with their given lighting conditions (because, again, the light source might be too bright), yet don’t find their vision actually impaired. Discomfort glare is also referred to as ‘psychologi- cal glare,’ as physiological tests can’t measure it and physiological values can’t account for it. Discomfort glare is measured and evaluated exclusively on the individual level. Despite many decades of research, the phenomenon and exact causes of discomfort glare still aren’t fully understood. Glare is one of the first elements requiring atten- tion in environments like offices, where both direct and indirect glare can impact visual comfort. In line with this, and also so as to provide a variety of op- tions in terms of archetype, design, and connectivity, the Philips office portfolio includes a variety of lumi- naires, such as SmartBalance, SlimBlend, and True- Line (office-compliant version). All have

minance that can potentially reflect off surfaces such as computer screens or glossy furniture. In conclusion, visual comfort is crucial to our well-being. In offices and other work environments it’s even more im- portant, as it makes us more productive. Glare, a com- plex phenomenon that comes in both direct and indirect forms, is a chief cause of visual discomfort – and even visual disability. With the right lighting, however, lighting professionals can mitigate or even eliminate it, improving the environments they’re charged to light and the way that people interact and work in them.

By Caglar Yilmaz and Gilles Vissenberg

Enquiries: www.lighting.philips.com

SPARKS ELECTRICAL NEWS

FEBRUARY 2019