Shining a light on high-CRI LEDs
These bulbs promise a professional level of color accuracy -- but which one do you want?
So far in 2014, we've seen the price of LED lighting drop while options continue to expand. With more and more consumers turning to LED bulbs to light their homes, how does a given light stand out from the rest?
At least two manufacturers think that the answer is color quality -- that is, a given bulb's ability to make reds, greens, and all other shades look just the way they should. Incandescents were notoriously good at this, but as consumers began replacing them, they realized that CFLs often weren't. Now, as LEDs become more and more mainstream, many of those consumers are worried about getting burned by bad-looking light all over again.
Cree's $16 TW Series LED and the $20 GE Reveal LED are two lights designed specifically to assuage those kinds of worries. Along with the usual efficiency and longevity benefits offered by standard LEDs, these bulbs also promise the sort of professional level of color accuracy usually reserved for photographers or art galleries. But which one does a better job of it?
Spotlight on the CRI score
A bulb's capacity for producing correct-looking colors is measured by its score on the color rendering index. This figure, usually referred to as the CRI number, is a score out of 100 that actually averages several scores together, each one for a different color.
A high CRI number is like a high grade point average for color quality. While most LEDs score in the 80s (a solid B average), both the Cree TW Series and the GE Reveal LEDs score in the 90s -- easily placing them at the front of the class.
We wanted to see these high CRI numbers for ourselves, so we brought out our handy spectrometer, the same device we used to test the accuracy of color-changing LEDs last month. With the spectrometer, we're able to take a closer look at the light output of a given bulb. This includes calculating its CRI score, shade by shade.
The GE Reveal claims a CRI score of 90, while the Cree TW Series LED claims 93. Sure enough, both bulbs scored in the 90s when we tested them out -- but interestingly enough, it was the GE Reveal that scored slightly higher, not the TW Series.
The difference is easy to spot when you take a look at the full color rendering breakdown for each bulb. The GE Reveal offers high marks across the entire spectrum, never scoring much below 80 with any color. Compare that with the Cree TW Series, which drops down to 59 in the red test, while also struggling with blue and yellow. It still offers color rendering that's far superior to standard LEDs, but compared with the GE Reveal, it seems to be a noticeably less capable light.
We wanted to know just how significant this difference really was -- which meant it was time to set the spectrometer aside, break out the camera, and make a quick run to the produce section.
A good color comparison shot should feature bright, vivid colors that anybody can recognize. In the past, we've used peanut M&Ms, since they're colorful and familiar to most everybody. For this go around, we decided to add some fruits and veggies into the mix.
We started with a bowl of berries, specifically to see how well the Cree bulb would do with red tones, which the spectrometer suggested it might struggle with. If we're going back to the GPA analogy, 59 is far from a passing grade, so you might think that those reds would look terrible.
As you can see, it's actually a rather subtle difference. Look at those strawberries. The saturated, red part of the berry is more or less the same in each shot, but the reflected light is much more yellowed under the Cree's glow (right) than it is under the GE Reveal (left) -- and that affects the color's overall appearance.
It's a more obvious difference if you look at the bowl itself, which looks much more white and natural in the GE shot than it does in the yellowy Cree shot. The background -- out-of-focus white cabinetry -- is another telling difference.
We moved on from berries through lemons, limes, oranges, peppers, and, of course, peanut M&Ms (you can click through our complete gallery of comparison shots to see for yourself). Throughout each test, both bulbs did a fine job, and certainly better than the average LED will do. Still, the GE Reveal always seemed to edge Cree out -- which was completely consistent with what we saw from the spectrometer's CRI readings.
All of this suggests that the Cree TW Series LED might skew slightly towards the warm yellowy light quality of the original Cree LED, which casts a much more noticeably golden glow.
A bump in brightness
One important distinction between the two bulbs that you'll want to keep in mind is that they don't offer equal levels of brightness. The Cree bulb puts out 800 lumens, which makes it a fair comparison to a typical 60-watt incandescent (the one we tested puts out 830 lumens). The GE Reveal, however, only puts out 570 lumens.
To understand why this is, you need to understand that these bulbs both filter out certain parts of the spectrum in order to improve overall color accuracy. This means that they don't shine as bright as they normally would, since less of the light produced is able to make it out of the bulb. Compared to the standard Cree LED, which puts out about 84 lumens per watt, the TW Series LED only puts out 59 lumens per watt. The GE Reveal is similarly affected, putting out just 52 lumens per watt.
The difference between the two is that Cree compensates for this decrease in efficacy by cranking up the wattage to 13.5. This makes for a bulb that uses a bit more energy, but which still manages to put out enough brightness to qualify as a true 60-watt replacement.
You can see this difference in the graph above, which shows how much light each bulb puts out at each point of the visible spectrum. Look closely, and you'll notice that the Cree's curve is just slightly higher than the GE's -- that's the extra wattage.
Now take a look at that big "W" shaped dip in the middle of each curve. Each graph swoops down twice, right over the yellow part of the light spectrum. What you're looking at is the light that's getting filtered out. As you can see, the swoop in the GE Reveal's graph falls lower, which tells us that it filters out a lot more of that yellow light. This explains why it looks a little less yellowy in our shots, and also helps explain why it's so much dimmer than the Cree bulb.
The bottom line
Each of these bulbs boasts a noticeably higher CRI number than the standard LED, but if I'm picking one out solely for its color-rendering abilities, there's no question that I'd go with the GE Reveal. In all of our comparison shots, it holds a slight yet consistent color accuracy edge over Cree -- an edge that was backed up in full by our spectrometer readings.
Of course, there's a lot more than just the CRI score to consider when buying the bulbs you'll be outfitting your house with. For starters, the Cree TW Series LED costs $16 -- $4 less per bulb than the GE Reveal LED (there's also a 40-watt replacement version that sells for $14). On top of that, Cree's bulb is brighter, lasts longer, and comes with a much longer warranty than the GE Reveal. As an overall value, the TW Series still looks pretty solid to me.