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Commercial Lighting Design Guide Appendix D
Doc 4775A 97
Grazing and Washing Surfaces
On walls or on the surface of an object, changing the way
light is focused produces different effects. To emphasize a
rough textured brick wall, graze the surface with light
striking the surface at a sharp angle. To emphasize a
smooth wall, wash the surface with light by striking the
surface at a wider angle.
Switch and Dimmer Locations
The proper location for a switch or dimmer is a function
of code requirements (the National Electrical Code
establishes some specific locations where control devices
are required) and common sense. For example, the code
requires a wall switch adjacent to the door upon entry to
a room. but you can also add a switch in a preferred
location, such as next to the bed.
Another choice are motion sensors that automatically
switch lights off when the room is empty, and they are
especially efficient devices in spaces like garages, utility
rooms and other spaces where lights are only needed
occasionally and are often left on inadvertently.
Crestron offers the most technologically sophisticated
products that permit handheld remote dimming, whole
house master controls, and many other features.
Color Temperature
Color temperature is the color of the light source. By
convention, yellow-red colors (like the flames of a fire) are
considered warm, and blue-green colors (like light from
an overcast sky) are considered cool. Color temperature
is measured in Kelvin (K) temperature. Higher Kelvin
temperatures (3600–5500 K) are considered cool and
lower Kelvin color temperatures (2700–3000 K) are
considered warm. Cool light is preferred for visual tasks
because it produces a higher contrast than warm light.
Warm light is preferred for living spaces because it is
more flattering to skin tones and clothing. A warm color
temperature of 2700–3600 K is generally recommended
for most indoor general and task lighting applications.
Color Rendition
Color rendition is the appearance of colors when
illuminated by a light source. Color rendition is generally
considered to be a more important lighting quality than
color temperature. Most objects are not a single color,
but a combination of many colors. Light sources that are
deficient in certain colors may change the apparent color
of an object. The Color Rendition Index (CRI) is a 1–100
scale that measures a light source's ability to render
colors the same way sunlight does. The top value of the
CRI scale (100) is based on illumination by a 100 watt
incandescent light bulb. A light source with a CRI of 80
or higher is considered acceptable for most indoor
residential applications.
Glare
Glare is primarily the result of relative placement of light
sources and the objects viewed. Often, it is excessive
brightness from a direct light source making it difficult to
see. A bright object in front of a dark background usually
causes glare. Bright lights reflecting off a television or
computer screen or even a printed page produces glare.
Intense light sources—such as bright incandescent
lamps—are likely to produce more direct glare than large
fluorescent lamps.