Category: Lighting Profession

LEDucation Update

LEDucation this year is on March 17 and 18 at the New York Hilton Midtown where I’ll be part of two presentations.  The first, at 9 am on Tuesday morning with Wendy Luedtke of ETC, is a seminar called Specifying Color Rendering with TM-30’s New Annex E.  The session presents the new ANSI/IES TM-30 Annexes E and F, which apply recent research to identify three color rendering design intents (Fidelity, Preference, and Vividness) and provides specifiers with TM-30 values to achieve them alone or in combination. Our goal is to increase awareness of Annexes E and F and to help attendees better understand their contents and use. The seminar is most appropriate for people with some prior knowledge of TM-30, although there will be a brief TM-30 overview for those who are new to the topic.

Then, on Wednesday, we’ll be joined by Jess Baker of Schuler Shook for a daylong demonstration of Annex E.  In the TM-30 Demo Room visitors will experience an immersive mockup illuminated with a variety of light sources illustrating the Annex E design intents. The lighting demonstrations will be paired with TM-30 values to show how TM-30 can be used to select light sources for each intent. Visitors will experience sources that meet different levels of the IES TM-30 specification guidelines outlined in IES TM-30-18 Annex E.  We’ll be presenting the demonstration on the hour and half hour from 9 am to 2 pm.

You can register to attend LEDucation here.

Using TM-30 to Improve Your Lighting Designs

Recently, ANSI/IES TM-30 was improved with the addition of Annexes E and F.  Annex F reviews and summarized five studies that explored using TM-30 metrics to predict subjective visual outcomes.  Annex E uses that research to establish recommended specification criteria when the designer’s color rendering goals are Preference, Vividness and/or Fidelity.

The IES Forum for Illumination Research, Engineering, and Science (FIRES) has an article I wrote with Michael Royer and Tony Esposito explaining the Annexes and how to use the information in Annex E.  Here’s the link: Using TM-30 to Improve Your Lighting Design – Illuminating Engineering Society

I’ve been using Annex E on projects and have spoken to other designers who have begun to use it.  It provides useful, accurate information that allows me to evaluate the color rendering results of light sources in a way that hasn’t been possible until now.  It lets me make informed decisions about my projects, and explain those decisions to colleagues and stakeholders in (relatively) easy to understand terms.

TM-30 and the TM-30 calculators continue to be a free download from the IES here.  Annexes E and F are also free on the Errata and Addenda page here and here.








The DLFNY Annual “Debate”

On February 28th I’ll be one of the panelists at the annual DLFNY “Debate”. Here’s how they describe it:

Join us for a fun and educational evening of lively, sometimes absurd debate between members of the New York City lighting design community. Enjoy a verbal joust as the debaters take sides on some of the most pressing topics in the lighting industry, during a light-hearted evening of discussion mixed with humorous provocation and competition. 
The topics have been chosen to provoke a dialog, so the opinions expressed by our panel may not be their personal stance, but will surely be interesting to hear.

You can find more information and register at DLFNY.com

NYT Talks Lighting Design, But Not With Lighting Designers

Sometimes the New York Times is oblivious and yesterday was one of them.  In an article titled Lighting a Room, Simplified the author wrote about the importance of lighting in the home.  In preparing the article, she spoke to and quoted four interior designers, one fixture manufacturers and  one professional lighting designer.  In addition, all eight of the photos in the article are taken during the day, so they’re nice illustrations of the use of windows and daylight in residential interiors but terrible illustrations of electric lighting, which is the topic of the article.  They seem to  be marketing photos for particular lighting fixtures, not examples of good lighting.

It’s too bad.  There are plenty of lighting designers who would have gladly shared their expertise and their work with the public if asked.  Unfortunately, this article is a reflection of the public’s (and the author’s) lack of awareness of the contribution good lighting, and therefore a good lighting designer, can make to a residential of commercial project.

Lighting doesn’t just come with a building.  Most interior designers and architect receive little or no training or education in lighting design when they’re in school.  Yes, some do have an affinity for lighting and can create beautiful work despite their lack of training.  However, the best lighting design is most likely to come from the best trained people – professional lighting designers.  If you are looking, one place to start is the IALD’s web site and the Find A Lighting Designer tool on the home page.








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.








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?








TM-30 Rf: So Big, So Strong, So Smart!

As we know, CRI Ra and TM-30 Rf are both measurements of color fidelity.  That is, they compare a test light source to a known reference light source and measure how well the test source matches the reference source.  One of the many shortcomings of CRI Ra is that it provides us with a single value.  That single value is easy to use, but doesn’t tell us anything about what colors will have increased saturation, decreased saturation, hue change, or will be unaffected.

TM-30 is a tougher test than CRI, so how do Rf and Ra values relate?  Lamps with Ra values below about 70 tend to have higher Rf values, while lamps with higher Ra values tend to have reduced Rf values.  Of course, this doesn’t mean that the lamps we think of as better have suddenly become worse, it’s just that we’re scoring on a different scale.  This means that we can’t draw direct comparisons.  For example, Energy Star requires that lamps have a minimum CRI Ra of 80, but that doesn’t mean that they should also have a minimum Rf of 80.  Different tests give different results and we have to be careful not to apply the meaning of one to the scores of the other.

IES TM-30’s Rf mathematically compares the appearance, under a test light source, of 99 color evaluation samples (CES) that are derived from real world objects, to the CES appearance under a reference light source of the same CCT.  The distance of the color shift for each CES is measured in the CAM02-UCS color space and averaged.  Throw in a lot of calculus (which we don’t need to get into) and voila, the Rf value.  It’s important to remember that what we get is just a number.  TM-30 doesn’t qualify any of the results as good or bad, desirable or undesirable.  It presents information to the lighting specifier and allows the specifier to apply education, professional experience, and knowledge about the project to determine whether or not a given light source is appropriate.

As with Ra, the single value of Rf conveys limited information.  It is more accurate, but still only tells us the average match or mismatch between the two light sources.  What makes TM-30 so powerful and useful is that it tells us much more if we want to know.  For example, using the Calculation Tool that can be downloaded with the purchase of TM-30 (which I wish the IES would make freely available), we can see that one common F32T8/830 has the following characteristics:

Rf   78
Rg   102
CCT   2943
Duv   0.0014
Ra   85

This lamp has moderately good fidelity (Rf), a slight increase in saturation (Rg), has a CCT of just under 3000K, and is slightly above the black body locus and therefore is slightly green (Duv).  The Advanced Calculation Tool tells us that the R9 value is 2 and that the Rf for skin is 85.  It also tells us the (x, y), (u, v), and (u’, v’) chromaticity coordinates (which, frankly don’t mean anything to me, but the information is there).  This information is immediately useful and isn’t provided as part of the CRI calculation.  In addition, most light source manufacturers don’t tell us the Duv, although understanding it is becoming increasingly important, especially now that NEMA has extended the chromaticity bins for LEDs in ANSI/NEMA C78.377 American National Standard for Electric Lamps – Specifications for the Chromaticity of Solid-State Lighting Products.  That’s a post for another time.

As I’ve already discussed, IES TM-30’s color fidelity metric Rf provides us with as little, or as much, information as we want.  If you just want top line information that the beige office you’re lighting will continue to look beige, you can have it.  An Rf of 78 is probably just fine.  If you want to see the fidelity of each of the 16 hue bins because you’re interested in the fidelity of a particular color range, it’s there.  If you want to know the Rf value of all 99 color samples you can have that, too!  What else?  Well, would you like to see the chromaticity coordinates in (x, y) color space, the SPD vs the reference source, or a pictorial comparison of each of the 99 CES?  No problem.

Pretty pictures but are they useful?  Not as useful as the data given above, but lighting designers do like to see this information, even if it’s difficult to interpret.  The CIE 1931 (x, y) color space isn’t perceptually uniform, so the distance we see between the reference source and the test source isn’t very informative.  Seeing the SPD is interesting, but no one can read an SPD and know what the light looks like or how it renders colors.  The CES Chromaticity Comparison is also interesting, but the red and black dots aren’t connected to one another.  With some light sources it’s easy to tell how they relate so we can see chroma and hue shifts, but as Rf drops and color shift increases it gets harder and harder.  What is useful are the next two graphics: the Rf value by Hue Angle Bin and by CES.

 

Now we can see how individual color ranges are affected by the lamp in question.  This may be especially useful on certain projects were specific color ranges are present and need to be accurately rendered.  The individual CES scores useful for the same reason.  However, in my opinion if you want information at that level of detail you’re probably better off doing a mockup and looking at project specific color and material samples instead of the CES.

TM-30 arms the lighting specifier with as much or as little information as needed on a particular project.  It also provides additional information that may be important (such as Duv).  It then allows the specifier to apply experience and knowledge about the client and the project to determine whether or not a given light source is appropriate.    Who could say no to that?