Residential Lighting - Illuminating Engineering Society

Iread Kevin Houser’s ‘Lighting For
Quality’ in November’s LD+A and
am very curious; unless I missed
something, why there was no mention
of the scotopic function and
the work that Sam Berman, Don
Jewett, Moji Navvab, Jim Sheedy
and others have done on scotopically
enhanced lighting.
LETTERS
TO THE EDITOR
Based on good science, there is
little doubt on the following points:
• Rods are active at normal interior
light levels
• Rods are the main controller of
pupil size
• More scotopic color in light
activates the rods = smaller pupils
• Smaller pupils = better visual
acuity and higher levels of brightness
perception
• These are important considerations
in many working environments,
especially with VDTs
If the author wants to bring up
any recent research that does not
confirm advantages of scoptically
enhanced lighting, I do not consider
it relevant, if 20/20 visual considerations
are not the governing criteria.
Stan Walerczyk, LC
Director of Lighting
Sun Industries
Concord, CA
Kevin Houser replies:
Mr. Walerczyk’s last sentence
struck me as remarkable. As I
understand it, he does not consider
spectral issues in lighting to
be relevant unless they are about
scotopically enhanced lighting
and 20/20 visual considerations.
Why would we limit ourselves to
these topics Different lighting
applications have different priorities;
while 20/20 considerations
like task visibility are often important,
so is the color of human
complexions, food, and merchandise,
the brightness of room surfaces
and objects, the visual efficiency
of electric light sources,
and perhaps above all the occupants’
satisfaction with the lighting.
These items are (partly)
dependent upon spectral power
distribution, of which the S/P
ratio is just one of an infinite number
of derived metrics. e.g. 1 - 28
Recent research also shows that
people may have different spectral
needs for visibility and circadian
photobiology; 29 as knowledge
in this area grows it may
influence architectural lighting
practice and the spectral design
of light sources. It is wrong to
presume that scotopic enhancement
is our only spectral variable,
and unjustified to assume that it
is the best way to improve the
spectral performance of light
sources.
Furthermore, a careful reading
of Berman’s work does not support
Mr. Walerczyk’s conclusions
about pupil size. While Berman’s
work contains much good science,
it is important to separate
the facts from the speculations.
Quoting Dr. Berman, “The spectral
response of pupil size has
been studied by several investigators
but there is no consensus
within the vision literature.” 1
Berman and his coauthors have
speculated that the scotopic
function governs pupillary response,
31-37 but, as far as I am
aware, they have not tested this
directly. Although it is not impossible
to make physiological inferences
from psychophysical experiments,
it must be understood
that these conclusions contain
speculation. I believe that other
viewpoints about pupil size and
brightness perception have been
prematurely dismissed or never
addressed by Berman and his colleagues.
For example, Alpern & Campbell
38 and Doesschate & Alpern 39
claim that pupil size is affected by
both rods and cones, and that the
action spectrum for pupillary
response peaks midway between
the photopic and scotopic functions
(near 530 nm). Independently,
Thornton has identified “a
particular set of primaries as an
invariant of the visual system,” 40
and has termed the regions near
450, 530, and 610 nm the “prime
color” regions of human vision.
Publisher
William Hanley, CAE
Editor
Charles W. Beardsley
Assistant Editor
Roslyn Lowe
Associate Editor
John-Michael Kobes
Art Director
Anthony S. Picco
Associate Art Director
Samuel Fontanez
Columnists
Emlyn G. Altman
Louis Erhardt • Stan Walerczyk
Willard Warren
Book Review Editor
Paulette Hebert, Ph.D.
Marketing Manager
Sue Foley
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