faces of the future - Illuminating Engineering Society

LETTERS
entities that are supposed to advocate
and support good design.
Hopefully, our final act (as you
wrote) will be a legacy of lighting
for human visual needs as we know
them to be, not a bus accident.
As Greg said, sustainable design
begins with sustaining people.
Bruce C. Dunlop, PLDA, IALD, LC
Bruce Dunlop Lighting Design
Lutherville, MD
The DOE Defense
The October issue of LD+A contained
several references to DOE’s
Solid-State Lighting program,
which I would like to address. First,
Dawn De Grazio’s letter to the
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editor pointed out the illuminance
requirements for the Walmart
Leavenworth site (“Whole Lot of
LEDs” June 2010) were not stated
and it was therefore difficult to
compare the 1000-W and 400-W
PMH and LED options presented,
each of which produced very different
illuminance levels. Good point.
The target illuminance level for the
front drive was 1.50 footcandles
(minimum) and for the main lot it
was 0.75 fc (minimum), both with a
max/min target uniformity of 10:1.
Second, I want to address a misunderstanding
evidenced in Alvin
L. Hart’s letter regarding my statement
in the August 2010 issue, which
read: “We hope it will be clear to Mr.
“Let there be light.”
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Warren that calibrated illuminance
meters of differing make/model may
yield different results. . . .” Mr. Hart
questioned how meters calibrated to
traceable NIST standards could differ,
the point of calibration being to
yield comparable results. In general
this is true, but meter calibration may
or may not include spectral correction,
cosine correction, or linearity,
and these parameters may vary substantially
between different make/
model illuminance meters. Some
calibration labs only test for one light
source, at one distance, and perpendicular
to the face of the sensor. We
recommend that readers check their
calibration reports for these details.
Also please see Robert E. Levin’s
seminal Photometric Connection columns
in LD+A, in which he notes,
“Thus, a statement of traceability in
itself is meaningless” (Nov, 1982).
Finally, I’d like to respond to the
“Energy Advisor” column, which
takes as its starting point my
August 13, 2010 Posting, a regular
e-mail newsletter I use to communicate
with the lighting and energy
efficiency communities about SSL
issues. Mr. Warren states, “The
DOE claims that an LED is 10 times
as efficient (efficacious) as an
incandescent lamp. That’s true for
the lamp itself, however, when you
include the optical, driver and thermal
losses, LEDs are only six times
as efficacious as incandescents. . .”
The passage Mr. Warren references
is forward-looking, not a statement
about current LED integral lamp
efficacy: “With the promise of
being 10 times more efficient than
incandescent lighting, LEDs will
change the way Americans light