deficient in blue and green, and tends to gray
these colors, it complements the appearance
of warm colors and human faces.
Incandescent lamps enjoy one slight
advantage over other lamps in color render-
ing—not because they render colors more
naturally, but because more than a century
of use has established them as a norm.
Incandescent lamps also produce light as a
by-product of heat, similar to other sources
of light that have been familiar for thousands
of years: the sun, open fire, candles, oil
lamps, and gas lamps. All of these give
warm-colored light and all arepointsources.
Good color rendition is usually inter-
preted to mean the familiar appearance of
familiar objects: things assume familiar
colors by frequently being seen under certain
kinds of light sources, such as incandescent
lamps or daylight.
Tungsten-halogen lamps (3000 K) have
more blue and less red energy than standard
incandescent lamps; they appear whiter
than the slightly yellowish standard incan-
descent lamps (2700 K). All incandescent
and tungsten-halogen lamps are assigned a
CRI of 100.
Fluorescent Sources
Fluorescent lamps produce a discontinuous
spectrum: peaks of energy at specific wave-
lengths. Variations in the composition of the
phosphorsthat coat the inside of the lamp
produce differences in the color of emitted
light. Three principal color temperatures are
available with fluorescent lamps: (1) warm
(3000 K) lamps are compatible with incan-
descent lamps, (2) cool (4100 K) lamps are
compatible with daylight, and (3) 3500 K
lamps are compatible with both.
Fluorescent lamps also fall into three
groups with regard toefficacyand color ren-
dition: standard, deluxe, and rare-earth.
Standard white lamps—both cool and warm
kinds—produce high efficacy and poor color
rendition (color plates 14 and 16). Warm
white fluorescent lamps have CRIs of 52 to
53; cool white fluorescent lamps have CRIs
of 60 to 62.
Deluxe white lamps produce improved
color rendering with an approximately 25 per-
cent sacrifice in lighting efficacy. The reduc-
tion in light quantity is often imperceptible,
however, because of the vivid and accurate
colors that improve contrast and portray
tones that are grayed with standard lamps
(color plates 15 and 17). Deluxe fluorescent
lamps have CRIs between 84 and 89.
For both high color rendering and high
luminous efficacy, rare-earth lamps are used.
Three kinds of rare-earth (RE) lamps are
available: triphosphor RE-70, triphosphor RE-
80, and quad-phosphor RE-90.
Triphosphor rare-earth lamps produce
light in accordance with the theory that the
human eye reacts to threeprime colors—
blue-violet, pure green, and orange-red
(color plate 18). When these three prime
(not primary) colors are combined in a
triphosphor lamp, only those wavelengths
are emitted; the brain fills in the remainder
of the spectrum. This yields more colorful
interiors because the three narrow-emis-
sion, prime-color phosphors compress all
hues into the eye’s color response system,
increasing color contrast (color plates 19,
20, and 21).
Because the eye/brain system can be
fully stimulated with these three monochro-
matic wavelengths, all pigment colors can be
rendered by adjusting the relative intensities
of the three prime-color phosphors. The key
is to choose the components that maximize
the visual system responses. For maximum
effect, the three wavelengths must corre-
spond to the peak spectral sensitivities of
human vision, which are near 450 nm, 530
nm, and 610 nm.
RE-70lamps use a coat of conventional
phosphors and a thin coat of narrow-emis-INTERIOR LIGHTING FOR DESIGNERS