“What manufacturers try to do
is emulate the color temperature
of daylight throughout the day to
be able to have higher blue con-
centration in the morning – so-
called alerting spectral properties
that also suppress melatonin for-
mation,” says Karlicek. “As the day
goes on into the evening hours,
you go to warmer temperatures
with lower blue content attempt-
ing to mimic what one might call
More broadly, tunable lighting
has been observed to improve
attention and behavior in cer-
tain settings. For example, high
color temperatures were found
to have a focusing effect in class-
room settings and other work-
places, according to a report from
Canadian utility BC Hydro.
“This was expected as midday
conditions exhibit high level cor-
related color temperature (CCT)
and luminance, and this is when
alertness levels are at their highest
and cortisol levels are also high at
this time of day,” the report notes.
“Under low CCT and luminance
level lighting, a calming effect was
seen in classrooms and hospital
patients. This was also expected
due to these levels of lighting
simulating times of day when
melatonin levels were higher and
alertness levels were lower.”
By creating more natural light,
it’s thought that tunable lighting
will stabilize circadian rhythms
and melatonin production for
workers, but the scientifically sup-
ported links have yet to be proven.
However, some manufacturers are
equating natural to healthy, which
is a gross oversimplification.
As with the results mentioned
in the report, most studies of the
health or behavioral effects of tunable lighting are anecdotal and
observation-based. While these
can provide some insights into the
effects of tunable lighting, they
can’t tell the whole story.
Tunable lighting in schools is a
common area to study, and
There are three main types of tunable lighting systems – each with its
own strengths and weaknesses.
Aiming to mimic incandescent lamps, dim-to-warm tunable lighting usually oper-
ates at color temperatures of 2700-3000K, and the light color becomes warmer in
appearance as lighting dims.
“There are a number of different ways of doing dim-to-warm. It typically involves
switching between cool and warm white LEDs. Some people add a red LED to get
the warmer color temperatures, but that’s a more complicated design,” says Bob
Karlicek, Director of Lighting Enabled Systems & Applications (LESA), a National
Science Foundation engineering research center at Rensselaer Polytechnic Institute.
Ultimately, dim-to-warm tunable lighting has limited potential for many commer-
cial spaces. According to the Department of Energy (DOE), dim-to-warm tunable
lighting is ideal in restaurants, hotel lobbies, guestrooms, ballrooms, theaters and
White tuning allows users to change the color of light from warm to neutral to
cool in appearance. These products have at least two sets of controllable LEDs, typi-
cally including a warm white color (around 2700K) and another at a cool white color
For facilities that want to dim lighting without affecting color temperature, white-
tunable lighting might be a very good solution.
“Sometimes users want to reduce light output without changing color,” notes the
DOE. “In these situations (such as in a conference room), it would be helpful to have
dimming control that’s separate from color change – so white-tuning might be the
Other benefits of white-tunable lighting, according to the DOE, include:
■ Providing apparent cooling or warming to a room. This includes psychological
effects like using cooler-color lighting to make occupants feel cooler on a hot day
or vice versa.
■ Matching the color of daylight in a lobby with windows by tuning the light to be
warmer early in the morning and late in the afternoon, while tuning it to be cooler
during the middle of the day, for example.
■ Assisting with behavior control. Anecdotal classroom studies suggest tunable
lighting can calm students, invigorate them or focus their attention.
■ Supporting the human circadian system. Tuning the intensity and the spectral
content of light can help stimulate or suppress melatonin production. These mech-
anisms aren’t fully understood yet but are a main area of focus for research.
■ Correcting circadian misalignment. Adjusting light color and intensity may be
used to treat jet lag, sleep disorders and other conditions.
The most sophisticated and experimental tunable lighting systems are color-tunable. They include at least three LEDs of different colors that can create a mixture
of light that is white, a tint of white or a saturated hue, explains the DOE. They can
provide a wider range of lighting color, but they require a much more complicated
“Color-tunable lighting consists of carefully timed and programmed control of
spectral power distributions with an eye toward replicating daylight variations
throughout the day to provide a low-blue content color tunable lighting at night,”
says Karlicek. “Those kinds of systems are still experimental and being developed.
They are increasingly being evaluated in research labs, healthcare facilities and