I’ve been running into people, Tweets, and marketing articles about full-spectrum lighting recently and I want to set some things straight. Full-spectrum lighting is a marketing term used by people selling you lighting products; it does not have any technical meaning in the lighting industry. Full-spectrum sources often cost much more than a standard product, sometimes more than 10 times the cost, and the overall benefits have not been proven.
Common claims:
- It is closer to “natural” daylight, which is its own benefit: This claim is more or less meaningless. Daylight changes throughout the day due to atmospheric conditions (is it cloudy or clear) and time of day (mid-day sun or morning sunrise). All artificial lighting sources are static in their output, what you get at 3:00 PM on a cloudy day is that same as 2:00 AM at night. Some LED sources are collections of LEDs that can be programmed to change color, but that has nothing to do with mimicking daylight. Trying to hash out the meaning of this claim gets you mired in spectral distribution curves which is a huge topic, so for now just keep in mind that “full-spectrum” sources are just modifications of existing fluorescents. Except GE Reveal and the like, which are modified incandescents.
- You get better color from full-spectrum sources: This is sort-of true. Full-spectrum fluorescents use a different phosphor mix that can sometimes have a higher CRI (color rendering index) than a typical fluorescent. The increase in CRI is often accompanied by an decrease in efficiency. You can also get non-full-spectrum fluorescents with higher CRI ratings than standard for slightly more cost than a standard lamp but still less than a full-spectrum lamp. The stand-out exception to this is the incandescent full-spectrum sources, which decrease the CRI of their bulbs.
- You get increased worker productivity with full-spectrum: There are two parts to this: the first is just based on the ability to see tasks well. In most circumstances productivity for visual tasks is linked to monochromatic tasks, such as reading black ink on white paper. For these tasks it is the amount of light that determines good visibility, not the color or quality of the light. In this regard full-spectrum offers no benefits. There is some research suggesting that since the rods–which are blue-green sensitive–control the size of the pupil, light to the cool, bluish side causes the pupil to constrict and thereby increase acuity and you can get equal acuity with less power by using bluish light. I think it is unreasonable to get into this kind of detail when you just want to buy a lightbulb, so the simple answer is “no.” However, if your work is very color sensitive, such as fine art or clothing production, you want to maximize the CRI of your sources to affect productivity.
- It has psychological benefits: This is the second part of the “increased productivity” claim. By definition, a psychological benefit is “all in your head,” so in terms of the benefit claim it is true. If you like full-spectrum lighting and don’t mind the disadvantages then you are getting a psychological benefit. Does everyone feel better equally, there’s no way to say, which is why it makes a good marketing claim. I have never found any research that shows a physiological link that leads to a psychological benefit. This is also often linked to the “natural” daylight claim. It is true that most people feel better working and living under daylight than artificial light. However, daylight changes throughout the day and with the weather, and I think the change over time is one of the main reasons people like daylight.
This post is getting longer than I like for a daily reading, so I’ll deal with the health concerns tomorrow. That will give you a chance to rest up and stay with me.
Tags: color, color temperature, CRI, fluorescents, full-spectrum, light bulbs
