Does it take a PhD to choose your LED lights?
We got this comment from Chris DeWeese, National Service Manager at Tosoh Bioscience, Inc. and it really sums up the frustration we hear from so many of our clients: "I've been in electronics and engineering for over twenty years with experience in a/v production and have no idea how to buy a light bulb today. I stood in the Home Depot aisle for ten minutes looking for a bulb to go over our vanity. I finally bought the round one."
Back in the early days the things we looked for when we specified light fixtures for a job were simple. Design and style were the main focus, since we practically knew how the fixture would illuminate the room based on a few very simple factors (shade material, wattage of the bulb, size of the fixture, etc). With the rapid take-over of the lighting industry by the new kid on the block, LED, things have, however changed drastically. We are now faced with terms we never had to deal with before: CRI (Color rendition Index) , lumens, Kelvin, CCT (Correlated Color Temperature), Color Quality Scale (CQS), CBCP (Center-Beam Candle-Power), efficacy and many more.
The sad thing is that it's not even enough to take a crash-course in this terminology and be done with it. These terms all have their flaws and are being heavily discussed within the lighting community. Just a few examples of many:
All lumens are not created equal: Looking just at the amount of lumens a lamp produces ignores how well the photons in the beam are focused and therefore how effective the lamp is. So two LEDs with the same amount of lumens on the box might very well appear to be of quite different brightness.Only advice here: Stay with the same brand and type if you have multiple light sources close together, since they might appear different.
CRI - A flawed metric? We all want to know how the light we buy will affect the surfaces, textures, surroundings we are going to illuminate. It doesn't matter if we are lighting our home or a restaurant or retail store, we want to be able to choose the right lighting for the specific situation. In some places accurate color rendering is extremely important and in others, like public parking lots, cost is more of a factor. (That's the reason you have a hard time finding your car in the parking lot at night, Low-pressure sodium lamps are horrible at rendering color, but very cost effective.)
The Color Rendering Index was developed to create some guidelines for labeling of lamps. Comparing two compact fluorescent lamps, one with a high and one with a low CRI would explain why the first one was a lot more expensive and why we'd choose that one to save energy in the living room and the other one for our garage.
The problems we are facing now are that the CRI was not developed with LEDs in mind. It has its issues, especially when it is used to assess the color rendering of the newest white LEDs.
Since there is not yet a better alternative, the lighting industry will, however, still use CRI as a metric for a while. A higher CRI number on the LED box usually means that the lamp renders colors more accurately.
Interesting tidbit: The Energy Star Label does not equal great color rendering. A high quality LED with superb color rendering might very well not be able to get the Energy Star label because it uses a bit more energy for this important benefit.
Here we go: photons, lumens, CRI..... Help! All we want is to light our home, not be overwhelmed with acronyms and complicated explanations. Light My Nest is working diligently on throwing some light on these subjects. Check back for more.
