Visible light from the sun contains all the wavelengths that our brains interpret as color. Initially we would perceive this as pure white light; but when this light strikes an object, that object may absorb certain wavelengths and reflect others. We only receive and interpret the wavelengths that are reflected toward us. So if a flower absorbs several wavelengths but reflects a wavelength that we interpret as red, we would call that a red flower.
Now imagine that same flower was only lit with a light that lacked "red" wavelengths. (Those that we see as red.) In this case, the flower couldn't reflect red toward us, so if we could see the flower, it would look black to us.
This is a simple example and represents a perfect scenario, but it tells us enough to talk about LEDs, color rendering, and an LED comparison with incandescent bulbs.
Since sunlight includes all the wavelengths we need for accurately seeing a color, it is given a 100 rating on the CRI scale. This same rating is given to incandescent and halogen bulbs, which also provide all wavelengths of light. But according to this chart from "Popular Mechanics," incandescent bulbs emphasize red and orange wavelengths over blues and greens.
(We should note that any specific bulb may show up differently on a chart like this.)
Still, this doesn't mean that other wavelengths are completely lacking in either CFLs or LEDs, but that we would be able to perceive some colors better or worse in comparison with other types of bulbs.
The traditional Color Rendering Index (CRI) is supposed to tell us how well a light source will let us perceive colors. And this index rates CFLs and LEDs well below the 100 rating of incandescent bulbs, usually in the low 80s. (Specific bulbs, however, are designed for a high CRI rating.) At a glance, this suggests that you'll most accurately see objects under incandescent lighting, and in that sense, incandescents are superior.
But clearly, when you look at the color chart above, CFLs could theoretically render certain colors very well; and LEDs, with a smooth color curve of their own, should render most colors very nicely, surpassing incandescents on greens and blues. And this is exactly why the lighting industry is now working on a new way of measuring color rendering.
HOW WE RAN OUR TEST
We did our own test to demonstrate LED lights against incandescent lights. The test looked at colored candies in a room with overhead lights turned off. The only lighting source was a single light bulb -- either incandescent or LED (two types were tested). We used a 60 watt incandescent and LEDs that are designed to replace 60 watt incandescents. The camera was set to not adjust the image and the flash was not used, so these images only represent how the colors appeared under the respective light bulbs.
Please note that we have shown the same incandescent image twice so you can more easily compare that to the LED bulbs we tested.
The Philips "Warm Glow" bulb is one that actually gets warmer (in color temperature, not in actual heat) when you dim it. This mimics the effect of a dimmed incandescent bulb.
WHAT WE SEE IN THE PICTURES
To our eyes, while rendering the background (table) with a little less red, the warm glow bulb provides a similar lighting level to the incandescent. It also seems to render colors almost identically in the candies. If we're to get really picky about it, we feel that the greens, yellows, and oranges are slightly more vivid under the warm glow light, while the reds have the edge under the incandescent.
Meanwhile, comparing the TCP LED, we feel the TCP is overall brighter so this may give us the sense of more vivid colors. That said, this time we perceive the blues, yellows, greens, and oranges to all be more vivid under the LED, while again the slight edge in red goes to the incandenscent.
Based on the color curves shown above, it absolutely makes sense that the incandescent would render reds better while the other colors might do better under LED lighting. That's what we're experiencing.
In any case, you may see what a subtle difference this is, and why the traditional CRI model doesn't make a lot of sense when buying LEDs. These bulbs do provide us with an excellent sense of color, and may be superior in some ways.
So what are your eyes telling you? We'd love your feedback as to which light you think provides the best image of these candies.