Autodesk LIGHTSCAPE, Manual

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Light and Color A
250
Lightscape
Luminaires
Luminaires emit energy in the visible spectrum. The
spectra of luminaires can vary greatly, depending on
the type of luminaire. The following illustration
shows the spectral curves for two different lumi-
naires. You can get the spectral curves for various
lights from lighting manufacturers, but they have
not yet adopted an industry standard format such as
the IES Data File Format.
Materials
Materials reflect some of the light that strikes their
surface. You can determine the reflected light from
the incident light by multiplying the reflectance at
each wavelength by the spectrum of the incident
light. The result is an intensity spectrum that repre-
sents the reflected light. The reflectance of the
surface at each wavelength is based on the type of
material and is described by a reflectance spectrum.
Materials reflect and absorb some of the light that
strikes them at each wavelength. That means that at
each wavelength, the reflectance of the surface is
greater than 0 and less than 1. In practice, reflectance
is significantly greater than 0 and significantly less
than 1. The following illustration shows the reflec-
tance curves of two different materials. The spectral
curves for materials are often difficult to obtain and
can vary greatly with different surface finishes and
with the age of the material.
Reflectance of Materials
The following table provides the average reflectance
for a variety of materials.
Material Type: Reflectance:
Nonmetals Soot, coal .05
Felt, black .18
Field, plowed .25
Marble, white .54
Oil paint, white .70
Paper, white .72
Metals Copper, tarnished .36
Stainless steel, polished .63
Iron, ground with fine
grit .64
Aluminum, polished .80
Copper, highly pol-
ished .82
Aluminum, highly
polished .90
Silver, highly polished .93