Measuring and Reporting LED Life

We’re putting the finishing touches on a lighting design and as we look at cut sheets we continue to be disappointed that many fixture manufacturers still don’t seem to understand the proper methods of measuring and reporting LED life. For example, an Edison Price cut sheet says that lamp life is “rated 50,000 hours based on L70/B50 criteria.  LM80 report by the LED manufacturer furnished upon request,” a USAI cut sheet says that life is “Based on IESNA LM80-2008 50,000 hours at 70% lumen maintenance (L70),” and a Lighting Services Inc. cut sheet just says “Tested to LM79 and LM80 Protocols” and then gives a life of 50,000 hours. Unfortunately, these statements don’t mean what the manufacturers suggest they mean. Let’s take a look.

Back in the early days of LEDs of lighting (say around 2005!) it was the wild west in terms of manufacturers reporting product life. The rated life of traditional lamps is the amount of time that passes until one-half of a sample set has burned out. LEDs don’t burn out, they just get dimmer and dimmer over time, so many LED manufacturers estimated the amount of time until an LED’s output had fallen to one-half and called that the LED’s life. This led to reported lifetimes of over 100,000 hours, which sounds great until you realize that at 100,000 hours the space you’re lighting is only half as bright as it was at the first hour. How many of our designs provide twice as much light on day one so that we can lose 50% of the light and still provide an acceptable light level? None! Clearly the industry needed another method of calculating life.

Eventually, the industry settled on a loss of 30% of output as the lifetime of an LED. This is in line with the Lamp Lumen Depreciation (LLD) factor applied to many CFL and HID lamps in illuminance calculations. The lifetime to 70% of initial light output is often abbreviated as L70. Many lighting designers have pointed out that a 30% loss of light is pretty poor performance and some manufacturers have responded by providing L80, and even L90, data (that is, the life until the LED has lost 10% of its initial brightness). All of this was a step in the right direction, but there was no standard method for taking the measurements to determine L70.

In 2008 the Illuminating Engineering Society stepped up to clarify things with LM-80-08 Approved Method: Measuring Lumen Maintenance of LED Light Sources. LM-80 (LM stands for Lumen Maintenance) specifies the test conditions and methods to be used to measure and report the lumen maintenance of an LED package. Data is collected every 1,000 hours for a minimum of 6,000 hours. Even accurately collected LM-80 data isn’t ideal, though. LM-80 is used to evaluate LED packages, not entire fixtures, so the conditions of the test (temperature, electrical characteristics of the driver, etc.) may, or may not, be similar to those in the assembled and installed fixture.

Importantly, LM-80 does not provide a method of extrapolating the 6,000 hours of data to predict future performance. As a result, any cut sheet saying that a 50,000 hour life is calculated according to LM-80 is misstating things unless the manufacturer has actually had the same LED packages under test. 50,000 hours translates to nearly six years, to that’s unlikely. LM-80 was revised in 2015 and is now the ANSI standard ANSI/IES LM-80-15 IES Approved Method: Measuring Luminous Flux and Color Maintenance of LED Packages, Arrays and Modules.

How do manufacturers calculate an LED’s life? They (should) use IES TM-21-11 Projecting Long Term Lumen Maintenance of LED Light Sources. TM-21 (TM stands for Technical Memorandum) describes a method for projecting the lumen maintenance of LEDs using the data collected during LM-80 testing. So, a cut sheet should say something like, “L70 life of 50,000 hours based on LM-80 testing data according to TM-21 protocol.”

The statements I quoted at the beginning leave wiggle room for the manufacturers to provide lifetimes that may, or may not, be calculated according to TM-21. TM-21 is the only standard we have that allows us to compare apples to apples, so omitting a statement about using TM-21 as the basis of lifetime calculation should make you suspicious about the reported life. It’s also important to understand that LM-80 is a testing procedure, and TM-21 is a calculation procedure. They are not tests. There’s no such thing as an LED that “passes” LM-80 or TM-21 (as some reps have tried to tell me). LM-80 and TM-21 produce information about the life of an LED that the designer uses to assess the appropriateness of a fixture.

Specifiers need to tell reps and manufacturers that LED life must be calculated according to TM-21. It’s the only way to be sure that the lifetimes of various fixtures are all calculated the same way so that we can make reasonable comparisons. They should also urge the IES to develop a procedure that tests a complete fixture: housing, power supply, and LEDs. That’s going to be the best estimate of the true life of an LED fixture. Yes it will take time, but we need accurate information that is calculated the same way across all manufacturers.

Why Hire A Designer?

We’ve had several people call this year to ask, “Why should I hire Studio T+L when the local sales rep/distributor has offered to do the work?” In one instance the caller was an interior designer we’ve worked with before who wanted help in explaining the role of a lighting designer to a client. In another, it was the client of an architect who was urging that we be brought on board as a theatre consultant. In all cases the owner was looking to save money, and saw adding another consultant to the design team as a potential waste of money. Nothing could be further from the truth.

Why Hire A Lighting Designer?
For starters, the local sales rep or distributor isn’t going to do the work of a lighting designer. She/he will suggest fixtures from the manufacturers that she/he represents. It will be up to the architect/interior designer/electrical engineer to determine if the suggested fixtures meet the project’s needs. What the rep or distributor won’t do is invest the time in meetings with the owner and design team to fully understand the project. The rep or distributor won’t develop a complete approach to the design that includes illumination levels, distribution, aesthetics, and controls. The rep or distributor won’t implement that design by selecting appropriate fixtures and controls, testing those selections through calculations or mockups, and creating the construction documentation. The rep or distributor won’t be available throughout construction to inspect the progress of the work, answer the contractor’s questions, focus the fixtures, and set levels in the control system.

Now, sales reps play a valuable role in acting as a liaison between the design community and the rep’s manufacturers. Distributors play a valuable role in procuring lighting equipment for the electrical contractor and delivering it to the site on time. To increase their sales, and their profit, they may offer assistance to architects, interior designers, electrical engineers, and owners, usually at no charge. That assistance may be useful, but no one should fool themselves into believing they are getting a fully developed design from someone who will participate in the project from start to finish. That’s what a professional lighting designer does, though, and is one of the reasons to hire one.

Why Hire A Theatre Consultant?
Theater consultants are hired for the same reasons as lighting designers, only more so, as we’ve written here. Designing a performing arts space requires extensive collaboration between the architect, owner, users, and theatre consultant, beginning with the very first meeting. The most obvious part of a theatre consultant’s work is designing and documenting the theatre’s special requirements – the form and layout of the theatre, space adjacencies, stage rigging, dimming and control, seating, etc. This work doesn’t happen in a vacuum. At Studio T+L we often say that design is as much a process as it is the product that is delivered at the end of that process. We listen carefully to the artists’ needs and desires, convey them to the design team in language they can understand, and advocate for those needs and desires throughout the design and construction process. We listen to the design and construction team and explain their needs and concerns to the artists. By assisting and guiding the collaboration we help to assure a successful project for everyone.

As in the lighting world, the local sales rep or distributor can’t and won’t design the project. Can they assist in a one-for-one replacement of old equipment? Absolutely. Can they sell the project a set of equipment (rigging, dimming, etc.)? Yes. But they will not, and cannot, provide impartial, wide ranging expertise from start to finish to develop, design, and build a fully thought out and integrated performing arts building. Those important services are only provided by a theatre consultant.

Edison Price “Light In Action”

A former student of mine who works for Edison Price Lighting is organizing a group of seminars they’re calling “Light In Action.”   It takes place here in NYC at EPL’s showroom and factory, and includes demonstrations of lighting techniques, discussions on the future of LEDs (led by a representative from Xicato) and dimming LEDs (led by a representative from eldoLED), as well as a factory tour.   Sounds fun, right?  There are six dates between now and the end of the year.  Visit EPL’s web site for more information.


For the second year in a row, USITT is promoting rigging safety on social media by asking people to use the hashtag #RigSafe on April 29th.  USITT will be promoting their Rigging Safety Initiative providing free rigging inspections and safety training for high school stages.  USITT is also producing the Jay O. Glerum Rigging Masterclass in Denver this June.

The importance of knowledgeable, safety conscious riggers is obvious when we consider that there are literally tons of equipment hanging over the heads of the audience and performers in many of our theaters.  USITT does a good job of offering training to high school and college students.  ESTA and their Entertainment Technician Certification Program (ETCP) take the next step by administering an industry-wide program of rigorous assessments for professional technicians in the categories of Rigger-Arena, Rigger-Theatre, and Entertainment Electrician.

These exams are a voluntary test of certain abilities, skills and knowledge in each category.  Individuals who have passed the exam have demonstrated proficiency in their respective field.  Studio T+L supports increased professionalism for entertainment technicians, and requires that an ETCP certified technician lead the rigging installation team on all of our projects.  We also encourage theatre owners and producers to support their technicians in attaining ETCP certified status.  ESTA offers ETCP exam guidance and information to organizations and individuals here.

MIT Creates Incandescent Lamp As Efficient as LEDs

Researchers at MIT and Purdue University have demonstrated an incandescent lamp with an efficacy of 6.6 percent, and with a potential efficacy as high as 40 percent. The paper was published in the April issue of Nature Nanotechnology. The demonstration compares favorably to current low efficacy fluorescent and LED lamps, while the upper limit is double the current maximum efficacy for fluorescents and LEDs.

The lamp uses a flat filament, rather than the coil of typical incandescent lamps, that is held between two plates of glass with a coating similar to a dichroic reflector, which the researchers call a photonic crystal. The plates permit visible light to pass through them, but reflect the infrared light back to the filament further heating it and producing more light. This idea has been with us for a while now, with most major lamp manufacturers producing some version of an IR halogen lamp. The main difference is that the new dichroic-like coating is much more efficient than the coatings currently in use and works at a much wider range of wavelengths and angles.

This is great news for those of us who haven’t bought into the idea that LEDs will make everyone happy, make all of our children above average, and help the country win the war. Between the low LPDs of the current versions of Standard 90.1 and other energy conservation codes, and the high efficacy of LEDs, most of us are compelled to use LEDs as the primary light source in many of our projects whether we want to or not. LEDs are great, but they’re not the best design choice for every application. As my students and readers of my book know, I regard energy efficiency as an important consideration in any lighting design, but not the primary goal. My first goal is to understand and deliver the desired look and feel of the space I’m lighting while providing appropriate light levels. My second goal is to explore the possible techniques and technologies that I can use to achieve my first goal. My third goal is to use the most energy efficient option from among the best options.

As a designer whose primary concern is the quality of the living/working/shopping environment I’m helping to create, I want to have as many tools at my disposal as possible, not just LEDs. At this point, it seems that lamp and fixture manufacturers are fully embracing the LED with very little attention paid to other light sources, with the possible exception of the OLED. If this experimental lamp becomes commercialized, we’d be able to use inexpensive, tried-and-true dimming technologies that deliver the performance we want without any of the problems associated with fluorescents and LEDs (flickering, flashing, dimming curves that are too flat or too steep, inability to dim smoothly to 0%, high cost, etc.).

This lamp wouldn’t be a solution for all lighting situations of course, in the same way that the LED isn’t a solution for all situations, but it would allow us to have true incandescent light in any application that called for it without running afoul of energy conservation codes. The best of all possible worlds!

IES Symposium Summary

If you missed IES Research Symposium III Light + Color you missed an exciting (for color geeks) few days. It would take too long to relate everything that was discussed, but here are some key highlights.

  • TM-30-15 is seeing broader acceptance throughout the industry. In an exciting development, it seems that the CIE is going to endorse TM-30 Rf after a few changes are made. The expectation is that the industry will then begin a rapid movement toward using Rf instead of CRI Ra, and that eventually CRI will be withdrawn. Unfortunately, the CIE is notoriously slow, so there is no timeline for their formal endorsement of TM-30. Maybe next year?
  • Manufacturers are resolving the spectral deficiencies that result from using a limited number of LEDs in both color mixing and color temperature tuning products. Their solution is to move from two and three color systems to systems using four or five independently controlled colors of LEDs.
  • Color preference was a big topic with no resolution. One complaint of both CRI and TM-30 is that they penalize light sources that deviate from the reference source even if many people prefer the deviation. Of course, Ra and Rf are both fidelity metrics, so they must penalize such deviations.   We have strong evidence that people prefer light sources that slightly increase the saturation of objects, and that people prefer light sources that include somewhat more red than the reference sources. However, because the amount of deviation that is preferred is application dependent, a single, all-purpose metric for rating color preference seems to be unattainable.

Southern Comfort at the Public

Our own Ed McCarthy is the lighting designer for Southern Comfort, which is playing at the Public Theatre through March 27th.  Charles Isherwood says that “This cast is entirely winning.”  So is Ed’s lighting design!  Read Isherwood’s review in The New York Times.

Design Is A Process, Not Just A Product

I often tell my students that design is as much a process as it is a product. Even so, they (and some of my clients) sometimes want to go from first meeting to finished design in one step. I suppose one could do that, but the result wouldn’t be a thoughtfully appropriate design, it would just be fixture selection. The difference lies in the early part of the design process where we gather information about the project and the expectations of the stakeholders, followed by an analysis of that information towards the stated goals of the project. Only after completing those two critical steps can we begin the work of putting the design together and executing it. Here’s one way of looking at the entire process.


What Happened to IYL?

Elizabeth Donoff asks “International Year of What?” in her editorial in this month’s Architectural Lighting, and I have to agree with her.  Early last year I noted that our professional organizations showed no plans to take advantage of the International Year of Light, and indeed nothing worth mentioning happened.  The professional societies of the lighting community (IES, IALD, etc.) added the International Year of Light logo to their web sites, but that’s about all.  They held no significant events, published no important documents, and made no efforts to raise the visibility of the profession with potential employers (architects and owners) or with the public at large.  The IALD boasts that their regularly scheduled events were added to the IYL calendar, but say nothing as to what resulted, probably because the result was nothing.  Lightfair 2015 was business as usual, I saw no recognition of IYL.

The entertainment industry did no better.  United Scenic Artists Local 829, the union for theatrical designers, didn’t recognize the opportunities, nor did USITT, and at LDI (the entertainment industry equivalent of Lightfair) there was no sign that anyone knew about IYL.

As I’ve written before (see here and here, for example), and as many of us know, far too many projects are built with poor lighting because lighting design is seen as an added cost that can be avoided by having the architect, electrical engineer, or lighting sales person provide the “design” instead of a trained, professional lighting designer.  Hoping this will change won’t change this.  On an individual level, designers can educate their clients about the benefits of thoughtfully designed lighting, but it takes a larger, more expensive effort to reach those who don’t interact with lighting designers.  Only manufacturers or professional organizations have the resources.

What could they have done in 2015, or what can they do this year?  For starters, I’d like to see the IALD and/or the IES sponsor  sessions on lighting design at the annual conventions of organizations such as  AIAASID, and SCUP.  Let’s get in front of the decision makers and teach them about what good lighting can mean to them.  Topics such as energy efficiency, code compliance, and daylighting, as well as the more artistic and aesthetic sides of lighting design, are all appropriate and would, I think, be well attended.  If we want lighting design to be seen as an integral part of any building project we have to work at it.  Adding a logo to a web site isn’t enough.