How Bright Are Colored LEDs?

Measuring and describing the brightness of colored LEDs is an increasingly important part of a lighting designer’s practice. They are used more often, and in more types of projects, than ever before. Yet, we don’t have an accurate method for understanding exactly how much light is being produced and how bright it will appear. It’s a problem that the lighting industry needs to solve, and soon.

The human eye does not respond to all wavelengths of light equally. We have the greatest response to the yellow-green light of 555 nm. Our response falls off considerably in both directions.  That is, wavelengths of light do not contribute equally to our perception of brightness. The sensitivity curve of the human eye is called V(λ) (pronounced vee lambda) and is shown below.

The definition of a lumen, the measurement of brightness of a light source, is weighted using V(λ) and essentially assumes that the light source emits light across the visible spectrum – in other words, it produces a version of white light.

Light meters are calibrated to measure white light using V(λ) so that their measurement of brightness corresponds with our perception. Individual colored LEDs emit only a fraction of the visible spectrum, as shown below in the graph of V(λ) and the SPD of a red LED, and that’s the problem.

Light meters measure the light that the colored LEDs provide, of course, and this information is included on an LED fixture manufacturer’s cut sheets, but it often makes no sense. For example, an RGBW fixture I’ve arbitrarily selected reports the following output in lumens: Red 388, Green 1,039, Blue 85, White 1,498. Since brightness is additive, the output when all LEDs are at full should be 3,010 lumens. However the Full RGBW output is given as 2,805 lumens! That’s 7% lower than what we expect.

The essential problem is that the colored LEDs give the light meter only a fraction of the spectrum it’s designed to measure. The meter provides a result based on its programming and calibration, but the results are often nonsensical or at odds with our perception. This problem doesn’t affect only architectural lighting designers. Film and TV directors of photography and lighting directors also rely on a light meter’s accurate measurement of brightness in their work, and when using colored LED fixtures the light meter is likely to be wrong. In fact, even white light LEDs can be difficult to measure accurately because of the blue spike in their SPD.

For now, the only way to accurately assess the brightness of colored LEDs is to see them in use. Lighting professionals need to let manufacturers and others know that the current situation is not acceptable, and that an accurate method of measuring and reporting the brightness of colored LEDs is a high priority. Talk to fixture and lamp sales reps, fixture and lamp manufacturers, and decision makers at IES, CIE, NIST and other research and standards setting organizations. There’s a solution out there. We need to urge those with the skills and resources to find it to get going!

LED Stage Light Reviews

We recently examined several LED stage lighting units for a high school black box theatre with a 20’ high grid. The school is determined to have an all LED system, but doesn’t have the budget for top-of-the-line equipment. Our goal was to find a set of lower priced units with reasonable performance. It turned out to be harder than we thought. Here are our reviews:

Altman Pegasus LED Fresnel. This 140W white light LED Fresnel is a winner. The optics are very good, the intensity is great, and the dimming (when controlled via DMX) is very smooth all the way out. This unit uses standard 7.5” accessories, so the school’s existing accessories will fit it. This is one of the more expensive unit we examined, but the performance makes this fixture worth it.

Chauvet Ovation E-910FC. This 270W profile has very high color rendering (due to the Red, Green, Blue, Amber, Lime color mixing) and great intensity.   The down side is that Chauvet’s optics are very poor. Whenever a shutter is used to shape the beam the multiple LEDs produce multiple shadows. This problem was evident for most of the second and third tier manufacturers. Although we didn’t test a template, we have to assume the same problem would occur, making this unit useless as a profile.

Elation Arena PAR Zoom. This 190W PAR has a motorized zoom, which simplifies making slight adjustments to the beam angle. The intensity was good, as was the dimming. The optics, however, were not. Each of the 19 LEDs has very good primary optics, but there is no secondary optic to homogenize the beam. This results in beam irregularities and produces multiple, clear shadows that would be unacceptable to an audience as close to the stage as they are in a black box theatre.

elektraLite 1018 PAR. This 216W PAR suffers from the same problem as the Elation PAR. There is no secondary optic, resulting in an unacceptable multiplicity of shadows.

ETC Source 4WRD Profile. This 155W white light LED profile is also a winner. The optics, intensity, and DMX dimming are all very good. This unit is $200-300 more than the other profiles we reviewed, but like the Altman Pegasus, its performance means that it can be used in the close quarters of black box theatres.

Osram Kreios Fresnel. This 80W white light LED unit has nice optics and an impressive zoom. The dim speed fading down to zero and up from zero is a little fast, but we think that can be managed by adjusting the dimming profile. Unfortunately, at only 80W this unit is too dim to be useful from a hanging height of 20’.

Osram Kreios Profile. Like the Osram Fresnel, this 100W white light LED unit also has nice optics and an impressive zoom. However, as with the Fresnel, it is better suited to smaller venues with lower hanging heights.

We plan on looking at other units, but our current thinking is that the school should have a base inventory of white light LED profiles (Source 4WRD) and Fresnels (Pegasus) that is supplemented with a small number of color changing profiles (ETC ColorSource).

LEDs In Stage Lighting

In a project meeting yesterday a team member said that LED stage lights would save the owner money.  While there are many reasons to include LED lights in a theatre’s equipment inventory, cost savings is not one of them.  We’ve written a white paper, LEDs In Stage Lighting, that includes an economic analysis and simple rate of return.  Get a copy here.

DOE Predicts LED Use and Energy Savings

The DOE has just issued, Energy Savings Forecast of Solid-State Lighting in General Illumination Applications (PDF, 116 pages), the latest edition of a biannual report which models the adoption of LEDs in the U.S. general-lighting market, along with associated energy savings, based on the full potential DOE has determined to be technically feasible over time. The new report projects that energy savings from LED lighting will top 5 quadrillion Btus (quads) annually by 2035. Among the key findings:

  • By 2035, LED lamps and luminaires are anticipated to occupy the majority of lighting installations for each of the niches examined, comprising 86% of installed stock across all categories (compared to only 6% in 2015).
  • Annual savings from LED lighting will be 5.1 quads in 2035, nearly equivalent to the total annual energy consumed by 45 million U.S. homes today, and representing a 75% reduction in energy consumption versus a no-LED scenario.
  • Most of the 5.1 quads of projected energy savings by 2035 will be attributable to two commercial lighting applications (linear and low/high-bay), one residential application (A-type), and one that crosses ­both residential and commercial (direc­tional). Connected lighting and other control technologies will be essential in achieving these savings, accounting for almost 2.3 quads of the total.
  • From 2015 to 2035, a total cumulative energy savings of 62 quads – equivalent to nearly $630 billion in avoided energy costs – is possible if the DOE SSL Program goals for LED efficacy and connected lighting are achieved.

Don’t have time for the full report?  Download the report summary.

Illustrated Theatre Glossary Now Available

There’s a funny, but true, phrase understood by theatre professionals and amateurs alike. “In is Down, Down is Front, Out is Up, Up is Back.” And that’s just the beginning! An architect or engineer designing a theatre will hear common words used in nonsensical ways.  For years we’ve kicked off projects by distributing an illustrated theatre glossary to everyone on our team.  We’ve found it to be very helpful, since architects and engineers usually don’t know the lingo of the theatre.  Now we’ve decided to make this short guide available to everyone.  Our Illustrated Theatre Glossary eliminates  confusion with clear definitions, descriptions, drawings, and photos. Definitions include:

  • Types of Stage/Audience Relationships
  • Spaces within a theatre
  • Stage directions
  • Theatre equipment

We hope you find it useful!

Lenore Doxsee Lights John Jasperse

Our own Lenore Doxsee will be lighting “Remains” a new work by John Jasperse at BAM’s Next Wave Festival this fall.  The dance piece will run from September 21 – 24 at the Harvey Theatre.  BAM describes the piece as “sampling fragments and phrases from the radical practices of his forbears while repurposing them within the contemporary present.”

Watch this interview with Mr. Jasperse.

What Will Your Last Broadway Show Be?

By Jason Livingston

When my nephew was eight years old he came to visit me in New York for the first time and I bought us tickets to see “Lion King.” I paid about $100 per ticket for orchestra seats just off of the aisle. It was a lot of money to spend on an eight year old, but I love the theatre and hoped to engender the same love in my nephew. During the spectacular opening number he was so excited! He was on his feet looking around, and at the end of the opening he turned to me with huge eyes and a smile that stretched from ear to hear and said, “I like theatre, Uncle Jason!”

A few years later his little sister, then also eight, came to visit and I bought us tickets to “Wicked.” This time tickets about $125 and we were in the mezzanine house right. They weren’t ideal seats but they were the best reasonably priced seats I could get. My niece was silent throughout the show, and silent for about 20 minutes afterward. Then, suddenly, she was done processing what she had just seen and spent the next hour or more excitedly telling me everything she loved about the show. She couldn’t stop talking about it and even now, five years later, she still listens to the soundtrack, and it is one of the most memorable experiences of her young life.

During subsequent visits I’ve taken the kids to see “Annie,” “Blue Man,” “Matilda,” “Pippin,” and last year won Uncle of the Year by taking my nephew to see “Hamilton.” How do you engage a 16 year old? Find the one show that combines popular music with one of his interests, American history. I loved it, too. It is easily the best Broadway show I’ve seen in a decade, probably longer. The music and lyrics are smart, funny, and sophisticated with a breathtaking blend of traditional Broadway and hip-hop that works beautifully. And I wonder if it’s the last Broadway show I’ll be able to take the kids to see.

Why? Partly because I paid about $130 for seats in the second to the last row of the balcony. We were so far away that it was very difficult to make out facial expressions. More importantly, though, Broadway ticket prices are about to soar.

On Tuesday the show’s creator, Lin-Manuel Miranda, published an op-ed piece in the New York Times. In it he complains that the average Broadway lover can’t get tickets because ticket brokers are using computer software, called ticket bots, to buy up tickets as soon as they are released and then reselling them at huge markups. Ticket bots are currently estimated to be buying up to 25% of the show’s tickets. He calls for the state legislature to pass a bill that will curtail the use of these bots so that average people can buy tickets.

In retrospect, one has to wonder if this wasn’t just a campaign to soften up the reader for Wednesday’s announcement that “Hamilton” was raising top ticket prices to an unheard of $849 for center orchestra seats, and that all other ticket prices were going up by 12% to 29%, from $139 -$177 to $179 – $199. How long will it be before other shows follow? Orchestra seats are already over $400 on quite a few shows, and if “Hamilton” can get away with extortion level pricing, can “Book of Mormon,” “Wicked,” and others be far behind?

 

“Greed Is Good” Gordon Gekko

“No it’s not” Most of Humanity

 

The thing about the announcement that really angered me is a quote from Jeffery Seller, the lead producer, who said, “What has certainly been frustrating to me, as a business owner, is to see that my product is being resold at many times its face value and my team isn’t sharing in those profits.” I’ve checked the Constitution, the Bible, and the Complete Works of William Shakespeare and nowhere does it say that he’s entitled to all of the money. Perhaps I should have checked the Complete Works of Donald J. Trump.

In one year the show has already recouped its $12.5 million dollar investment, and is making an estimated $600,000 per week in profits. It’s on track to join “Wicked” with $1 billion (with a B) in sales. Last month the show cancelled $10 million in bulk ticket purchases because it suspected that ticket bots were involved, and in the next round of tickets to be release there will be a maximum of six tickets per purchase. The show is doing great, artistically and financially, and is taking big steps to limit ticket bot purchases. So what’s really going on here? I have to believe that it’s simple greed. And, while that greed may be great for this show’s investors, I worry about its impact on the theatre at large and the people who love it. Think about it – two tickets at $845, plus taxes and fees, will cost about $1,750. That’s more than my mortgage!

The show’s producers point out that there’s a ticket lottery – 46 tickets at $10 for each performance. However, that’s only 3.5% of the seats. 10,000 people per day enter the lottery for those $10 seats. Assuming that the seats are awarded in pairs, you have a .23% chance of winning seats. With those odds you can’t make plans to see “Hamilton,” you can only hope.

My youngest niece is two. I worry that in six years I won’t be able to take her to see her first Broadway show because two tickets will cost $500 or more. I won’t be able to pass on my love of great theatre, or at least not my love of great Broadway theatre. Is Broadway going to become like most opera, the domain of the rich, or will it remain accessible to all of the people who love it?

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.