Night Shift? Not Quite.

We’ve all heard about the effect blue light can have on our circadian rhythms.  It can suppress the release of melatonin, which can delay sleep and reduce sleep quality with possible long-term health consequences.  Circadian disruption has been associated with depression and increased risk of diseases such as diabetes, obesity and cancer.

Back in 2016 the AMA released a report recommending night-time outdoor lighting have a color temperature no higher than 3000 K to limit night-time exposure to blue light.  That report was quickly criticized by the Lighting Research Center and the IES, among others, as I noted here and here.  One of the key criticisms was that correlated color temperature is a poor measure of spectral content and says nothing about the amount of energy in the wavelength range that affects our circadian rhythms.  A better measurement is melanopic content, which isn’t discussed in the report.

Last year Apple unveiled a feature in their OS and iOS called Night Shift.  When enabled it causes the color of the display to become warmer in the evening.  The assumption, the same as the AMA’s, is that warmer light has less blue so it won’t impact melatonin production.

A recently published paper in Lighting Research & Technology looked at the effectiveness of Night Shift.  This preliminary study suggests that “changing the spectral composition of self-luminous displays without changing their brightness settings may be insufficient for preventing impacts on melatonin suppression.”  Even when Night Shift was used, the devices still suppressed melatonin production.  The authors noted that, “it is not known how this amount of suppression induces circadian disruption, delays sleep or affects health.  Larger, more comprehensive epidemiological studies should investigate how the long-term use of these self-luminous displays affects people, especially adolescents and children.”

While additional studies are clearly needed, it provides additional evidence that lower CCT alone is probably not enough.  With our display devices we should also lower the brightness.

IALD – News – International Association of Lighting Designers

The linked article is on the web site of the IALD and concerns Louisiana State House Bill 748 which would prohibit the use of the terms “registration” and “certification” for nongovernmental professional credentialing.  The problem for lighting designers is that it would mean we couldn’t say that we were Lighting Certified (LC) by the NCQLP or that we were a Certified Lighting Designer (CLD).

No doubt there are other professions that would also be harmed by the bill.  The next vote is scheduled for May 9th.  If you want to let them know what a bad idea this is, contact the bill’s sponsor Julie Emerson.

Source: IALD – News – International Association of Lighting Designers

Design for Color and Illumination Webinar April 19th

On April 19th Wendy Luedtke (my co-chair of the IES Color Committee) and I will be presenting a free IES webinar called Design for Color and Illumination.  Here’s the blurb from the IES site:

When developing a lighting design, lighting specifiers determine the lamp and fixture combination that best suits the design’s requirements based on many factors. While some considerations are largely technical, such as power consumption, the amount of light generated, and how light is distributed, one consideration is both technical and artistic and can be approached in a number of ways. Participants to this webinar are eligible for one (1) IES Continuing Education Unit (CEU).

The webinar is at 12 noon EDT.  Register here.

Outdoor Night Time Lighting May Reduce Crime

I’ve just learned about a study conducted last year for the New York City Housing Authority (NYCHA).  In a randomized trial 39 NYCHA sites received additional night-time lighting for 6 months, while 38 sites received no additional lighting.  The study showed these reductions in crimes:

Index crimes: 7% reduction in overall index crimes (day and night). This reduction in overall index crimes was driven by a 39% reduction in index crimes that took place outdoors at night.

Felony crimes: 5% reduction in overall felony crimes (day and night). This reduction in overall felony crimes was driven by a 30% reduction in felony crimes that took place outdoors at night.

Assault, homicide and weapons crimes: 2% reduction in overall assault, homicide, and weapons crimes (day and night). This reduction in overall assault, homicide and weapons crimes was driven by a 12% reduction in assault, homicide and weapons crimes that took place outdoors at night.

Misdemeanor crimes: No detectable change in net misdemeanor crimes in treatment communities.

The results of other studies have been mixed, but I’m not clear if they were controlled, randomized studies.

The disappointing thing, from a lighting designer’s perspective, is the data that’s missing.  The report tells us the fixture wattage and lumen output, but doesn’t tell us the area covered or measure the increased light levels.  Instead it treats light fixtures as fixed items and counts them per square block.  This method would be fine if the world had only one type of outdoor fixture, but it doesn’t  So more light is better, but it doesn’t say how much more or what the upper limit should be.

Transforming Patient Healthcare and Well-being Through Lighting

Recently, the Illuminating Engineering Society (IES) and Center for Lighting Enabled Systems & Applications (LESA) at Rensselaer Polytechnic Institutesponsored a workshop to explore pathways to define and promote the adoption of lighting systems specifically for healthcare environments.  The aim of the workshop was to initiate an important discussion among diverse stakeholders on the changes in modern healthcare interior lighting applications. The result is the release of a white paper detailing the outcomes and contributions of the participants.

Source: Transforming Patient Healthcare and Well-being Through Lighting | IES

I’m Presenting at LEDucation 2018

This year LEDucation, the largest LED only trade show and educational forum in the U.S., will be on March 13 and 14.   On Tuesday the 13th from 11 am to 12:30 pm I’ll be presenting a forum called How To Use TM-30, along with Dr. Michael Royer of Pacific Northwest National Laboratory and Wendy Luedtke of ETC.  Here’s a summary of the event.

This presentation discusses a number of design trends that are currently shaping the industry and promising to redefine the role of lighting as we know it. New technologies are making dimensions such as color and dynamic behavior over time viable for main-stream lighting, and that constitutes exponential change. This presentation explores a few of the dimensions that appear to be gaining traction, and attempts to illuminate some of the reasoning behind their development. Implications to the user experience are discussed, along with the inadequacy of present lighting metrics.

See you there!

TM-30 Rg, The Gamut Index

In addition to an index that measures the fidelity of a light source to its reference source (Rf) IES TM-30 includes an index that indicates the change in saturation of colors called the Gamut Index and abbreviated Rg.  Rg is calculated using the same Color Evaluation Samples (CES) and underlying calculation engine as Rf, which makes TM-30 a cohesive system.

Here’s how Rg works.  An Rg value of 100 indicates that, on average, the light source in question does not change the chroma, or saturation, of the 99 CES when compared to the reference light source.  An Rg value below 100 indicates that, on average, the light source renders colors as less saturated than the reference source, and an Rg value above 100 indicates that, on average, the light source renders colors as more saturated than the reference source.

Since Rg is an average it says nothing about the possible change in chroma for any individual hue angle bin or for any individual color evaluation sample.  That’s ok, thought, because TM-30 also tells us the Rg values for each hue angle bin, and for each CES.

Here’s an example of the graphic for the hue angle bins using the same light source as the previous post on Rf.

TM-30 doesn’t recommend any particular Rg or set of Rg values.  As with Rf, the interpretation of the information is left to the specifier.  Acceptable or desirable values will vary by application.  Rg doesn’t have a maximum or minimum value, but the possible range increases as Rf decreases, as shown below. The wedge to the left of the gray lines shows the range of possible Rg values, while the red dot represents the lamp we’ve been discussing.

The Rg values are also presented in a Color Vector Graphic (CVG), as shown below.  The white circle is the normalized reference source.  The black circle is the lamp in question.  Where the black circle is inside the white, colors are desaturated.  Where the black circle is outside of the white, colors have increased saturation.  The colored arrows indicate the direction of saturation shift, and the direction of hue shift.  Arrows that point straight in or out show only saturation shift.  Arrows that show rotation left or right also indicate hue shift.  I know!  And, the next version of TM-30 will present a graph showing the hue shift!

 

Research is revealing that we shouldn’t treat all hue angle bins the same.  Bins 1 and 16, which include the most red, are indicative of preference and it seems likely that they will take on increasing importance in that role.  Some specifications are already acknowledging this.  For example, the Department of Defense recently re-issued the Unified Facilities Criteria for Military Medical Facilities that establishes the following requirements for light sources:

Fidelity Index: Rf ≥ 80,

Relative Gamut Index: 97 to 110,

Fidelity Index, Hue-Bin 1:  ≥ 78,

Chroma Shift, Hue-Bin 1: -9% to +9%.

Clearly, TM-30 permits us to be much more specific about the color rendering that is acceptable or desirable for a project.  Why bother with CRI anymore?

Focal Point Introduces TM-30 Based “Preferred Light”

Today Focal Point Lights of Chicago, IL introduced a series of fixtures that feature what they call Preferred Light.  Preferred Light is based on recent studies at PNNL and Penn State, plus their own study, and uses TM-30’s Rf, Rg, and Hue Bin 16 values to establish a balance of fidelity, saturation, and red rendering that is “visually appealing to humans.”

The overall idea is that people seem to prefer a light source that slightly over saturated most colors, especially red.  “Using a custom LED mix, Focal Point defines Preferred Light using TM-30-15 metrics as having a fidelity (Rf) of 89, a gamut (Rg) of 107, and over-saturating Hue Bin 16, deep red content, by 9% at a [Correlated] Color Temperature of 3500K.”  So, by using the statistical measures of TM-30 and applying them to the related topic of color preference Focal Point has identified an optimized set of LED products to meet their customers’ needs.

I’ll be the first to admit that it may be risky to base all of this on only three studies, but other studies have shown that the TM-30 results can be applied in this way, and are also showing us the relative importance of the various calculated values.  I’m excited to see the industry using the tools, and am looking forward to seeing the Preferred Light for myself.