COMMeMOratiVe ISSue - Illuminating Engineering Society

e s e a r c h
M A T T E R S
To help the IESNA “celebrate the past and imagine the future,”
five scientists from the Lighting Research Center offer their perspectives
on where lighting research is headed. John Bullough
explores when to use lighting, not just how much; Yukio Akashi
explains how research can help drive sustainable design; Mariana Figueiro
notes that lighting’s impact goes beyond visible light; Conan O’Rourke looks
at the future of fluorescent lighting; and John Van Derlofske says lighting for
our roadways must convey meaningful information to drivers.
From “How much” to
In the century ahead, time will
“When”
matter in research and application.
John D. Bullough
Our increasingly brighter nighttime
The IESNA has long produced sky, for example, reduces our ability
guidelines for lighting in various
applications, via its Lighting mining if and when to turn lights
to understand our universe; deter-
Handbook and recommended practices.
Most recommendations focus important question. We know that
off outdoors (curfews) will be an
on the appropriate quantity of light morning light exposure has a different
effect on the human circadian
for buildings and roadways. Efforts
to quantify the illumination necessary
for visual performance filled the tical lighting. [6] Shrinking energy
system than night exposure to iden-
20th century. [1-3] Even with recent resources will make controls more
efforts in lighting quality, recommendations
still use numbers like lation. The IESNA must exercise
significant in every lighting instal-
luminance ratios. The 20th century wisdom in encouraging research to
also taught us that not all footcandles
are equivalent. Some lamps lighting is appropriate in the world
study when, not only how much,
outperform others for rendering colors;
life illuminated entirely by low
of the next century.
pressure sodium, despite its efficacy,
[4] would not be so enjoyable. Lighting
Towards Sustainable
Various color-related indices help us Yukio Akashi
understand lighting better than if we In the last century, the effects of
know only the quantity. Often, common
expectations about appropri-
were studied on the basis of bio-
light levels on visual performance
ate relationships between light and physics. Those studies established
color can guide us, evidenced by the models in which visual performance
Kruithof curve in today’s Handbook. for a given luminance contrast was
More recently, we’ve learned how described as a plateau and an escarpment
as a function of illuminance. [1]
different lamps outdoors can impact
peripheral visibility, even at the same IESNA’s illuminance recommendations
are not determined by nighttime level. [5]
visual
performance alone, but rather are
subject to many other forces. [7] Until
fluorescent lamps replaced incandescents
in the 1940s, practical
illuminances tended to fall on the
escarpment. Afterward, illuminances
reached the plateau, where performance
is less sensitive to changes in
illuminance. Since then, illuminance
standards have been affected by
economic and energy concerns.
Obviously, sustainable lighting
will play a major role in the coming
century. One way to facilitate this is
to reduce illuminances for regular
tasks without impairing visual performance.
A recent demonstration study
using a simple retrofit task-ambient
lighting technique addressed
this question. [8] This demonstration
study reduced ambient illuminance
by removing one lamp from every
three-lamp fixture while maintaining
task illuminance. This de-lamping
resulted in a change in ambient illuminance
from 550 lx to 350 lx. Workers
accepted this illuminance reduction
after a short period, although they
initially did not prefer it. The same
demonstration study suggested that
the use of a lamp with relatively
more short-wavelength components
significantly helped maintain room
brightness. Room brightness is an
essential element of lighting quality,
as many studies have suggested. [9]
To further facilitate acceptance
of sustainable lighting design for
new construction and other applications,
we must implement measures
that enhance room brightness while
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