What is
light?
What our retinas perceive as “light” is just part
of a wider range of electromagnetic radiation produced in the
form of waves. The intensity of light waves creates their color. Infrared rays, ultraviolet rays,
X-rays, radio waves, and heat are part of the spectrum that
we can’t see.
We think of midday sunlight as the standard for pure white light
color. When daylight is passed through a prism, however, it
is actually rendered as equal parts of a continuous spectrum
including red, orange, yellow, green, blue, and violet.
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In contrast, artificial light sources give off varying
amounts of color. Incandescent light includes most of the
spectrum but has a large proportion of yellow and red. When
dimmed, incandescent light becomes even redder.
Many people think fluorescent light as being low in red and
high in green and blue light waves, but in fact fluorescent
tubes now come in more than 200 colors. Quartz halogen produces
brighter, “whiter” light than either incandescent
or fluorescent sources; it’s popular for commercial
display and museum lighting as well as for residential accenting.
Light bulbs are formally rated by color temperature, measured
in degrees Kelvin (K). Temperatures below 3,500 degrees K
are warm-toned; higher temperatures are increasingly blue,
or cool. The chart at right shows the position of several
standard light sources on such a “thermometer.”
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Color rendition
How we perceive the color of an object is determined by two
things: the surface color of the object itself and the color
in the light that shines on it. The color of a blue vase under
a blue light will be heightened, because the color of the light
intensifies the blue of the vase. Under a red light, the same
blue vase will appear dull and grayish, because the red light
waves are absorbed and there are no blue waves to be reflected
by the vase. Because lighting can
affect the apparent color of fabrics and wallpaper, it’s
always a good idea to choose furnishings and decorating materials
under the same type of light you’ll be using at home.
If possible, bring home a swatch of material or a paint sample,
or take sample materials to a lighting store. Today’s
“light labs”- showrooms where you can directly
compare light sources - make this evaluation a lot easier.
Reflectance
The colors and textures of a room’s walls, ceiling, and
floor not only affect the room’s décor but also
contribute to the general light level according to their reflectance-
that is, the degree to which they reflect light. Colors and
textures of furnishings and display objects can affect overall
lighting levels, too. Colors that
contain a lot of white reflect a large amount of light, of
course, while darker colors absorb more light. A white object
reflects 80 percent of the light that strikes it, while a
black object reflects 5 percent or less. The illumination
in a room with light-colored walls is distributed farther
and more evenly as it is reflected from surface to surface
until it gradually diminishes. For this reason, if you were
to redecorate your living room by covering creamy white walls
with a rich blue wallpaper, you’d find that you needed
more light sources and bulbs of higher wattage to reach the
same light levels as before.
Texture plays a part in reflectance,
too. Matte finishes diffuse light; glossy finishes bounce
light onto other surfaces. Thus, a room with fabric-covered
walls requires more fixtures or brighter bulbs than a room
with painted walls in order to achieve the same level of light.
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