LED House Lighting – We've still got a ways to go...
by Ken McKibben, on Jul 4, 2013 10:37:00 AM
As I'm sure everyone is aware, LED light technology is riding an explosion of popularity and marketing that can't be stopped. If manufacturers can cram an LED in it, they have, and with good reason. The compact, power-saving capability of this technology offers a lot of bang for your buck and solves a wide range of problems. It won't be too long before everything with a light source is LED, but we're not quite there, yet.
Theatrical, stage and broadcast presentation still presents considerable obstacles for this re-invented technology from the 1960s. Recently we've dealt with a lot of confusion from clients who are convinced that LED is the answer to every lighting need. While there are some very compelling applications for their use, it may be a while before LED house lighting in churches, museums and presentation-based spaces is a reality. Here's why...
LEDs don't work the same way as a traditional incandescent lamp. While incandescents are dimmed by reducing the electrical voltage, LEDs are dimmed by blinking them on and off very rapidly. While it is too fast for the human eye to detect, the blinking can manifest as flicker in high-definition video cameras based on a number of factors including the camera's frame-rate and shutter speed.
So it's important when evaluating a particular LED fixture for use in a facility incorporating video cameras to be sure that the frequency of the fixture is not a problem. Much of this is determined by the electronic driver that powers the LED bulbs. Unfortunately, most affordable architectural fixtures are currently designed for commercial environments where video cameras are not a consideration.
Constant Dimming to Zero
In many “dimmable” fixtures the dimming is very “steppy”, meaning that as you fade from 100% down to 0% the fixture steps down in increments rather than smoothly moving down in value. This steppiness is a function of how the electronic driver varies the rate of the pulses that determine how bright an LED light appears to be.
Another common problem with commercial architectural LED fixtures is their inability to fade below a certain percentage. In these instances the LED fades from 100% down to 10%, 15% and, in some cases, 25% and then drops out.
On a recent museum project, we had a presentation that involved bringing the house lights down just as a dramatic presentation began. Unfortunately, the electrical engineer specified and installed LED fixtures that were incapable of dimming to zero smoothly. With colored LEDs in the troughs overhead and the surround sound building anticipation for the upcoming presentation, the perfect mood was established. Then just as the video began to play the house lights dumped out and left the audience wondering who turned out the lights.
As mentioned before, most architectural fixtures are designed for commercial environments like offices, so smooth fades aren't high on the list of design criteria for manufacturers. This clunky dump at the end of a fade is very distracting and completely unacceptable for any presentation that requires a smooth transition to darkness.
All light has an overall color that is described as its color temperature and is measured in Kelvins. Color temperatures above 5000K are described as cool (bluish), and colors below 3000 are considered warm (yellow/orange). If you've ever looked out the window in the late evening and noticed that everything is totally blue outside while everything inside looks orange, then you've seen a perfect example of differences in color temperature. Natural daylight is on the cooler end of the scale and most traditional incandescents fall on the warmer end. As such, everything outdoors will tend to look blue while everything inside has a nice warm glow.
Color temperature is a very important factor when considering LED fixtures for a performance space. If video cameras are involved this factor is critical because the camera is much more sensitive to color temperature than the human eye. A few hundred degrees too warm, and the world appears to be on fire. Too cool and everyone looks like a Smurf. Unfortunately, many of the LED fixtures currently on the market have color temperatures that are abnormally low or high for normal presentation uses. It's important to verify that the color temperature is in the appropriate range as early as possible into a construction project.
Additionally, LEDs produce light in a very different way than conventional incandescent lamps. This difference can lead to a substantially lower ability for the light to render all of the colors in the spectrum in an accurate way, which is described as it's color rendering index (CRI). CRI is rated on a scale from 1-100. The lower the CRI rating, the less accurately colors will be reproduced.
If the CRI is too low, strange things can happen! I've seen people with light colored skin turn dark and splotchy and certain colors have seemed to glow eerily under low-CRI light. While great strides are being made in this area, it's another important factor to consider during the decision-making process.
Ultimately, the biggest issue with LED house lights for performance venues is the output. To put it simply, they're not quite bright enough.
On a recent project we were asked to put together a package for house lighting in a 600-seat church sanctuary. The ceiling was approximately 30ft. up, and there was simply no practical way to affordably provide even coverage at adequate light levels with available LED products. The time will come, but we're just not quite there, yet.
While there are a host of advantages offered by the advent of the LED craze, it's important to understand the pros AND cons before making a decision. In summary, these are the questions you should consider:
- Will the fixtures present flicker problems on-camera?
- Will the color temperature match the other fixtures in the room?
- Will the color of people and objects present unexpected color anomalies?
- Will the fixtures fade smoothly or will choppy fades present a distraction?
- Will the fixtures be bright enough for your needs?
It won't be long before LED architectural lights will be capable of meeting the unique challenges of presentation facilities. With a reliable systems integrator by your side, you can be educated on the options and make the best choices for your project every time.