What is full spectrum lighting?
Research from the 1960s has demonstrated the remarkable effects specific wavelengths of light have on the health and vitality of plant and animal life.
Most interesting was the finding that - even in the absence of natural sunlight - an artificial light source containing a fuller, more complete spectrum of visible light (particularly towards the blue wavelengths) would have just the same effect on plant growth as natural sunlight.
For this reason, we commonly define full spectrum lighting as a light source with a color temperature between 5000K and 6500K and a CRI above 96.
However, natural sunlight contains more than just a full visible light spectrum. Plants and animals also rely heavily on some other non-visible light spectra, such as ultraviolet and infrared.
As we'll soon see, just like the changing sun, there are different "types" of full spectrum light, and as such, there exists no singular definition of a full spectrum light bulb. Depending on your needs and desired effects from your lighting, some bulbs may work better than others. Read on for a bit of insight!
Full spectrum lighting can mean any bulb that either:
A) contains a full visible light spectrum and the non-visible light spectra of infrared and ultraviolet.
B) contains a balanced and full visible light spectrum.
Background on the electromagnetic spectrum
To understand what fullness of spectrum means, it would be helpful to understand the entire light spectrum - which includes more than just the whole rainbow constituting visible light!
The visible spectrum of light - white light comprised of the rainbow of colors - exists as a narrow band of frequencies, with each color representing a specific frequency range.
Visible light occupies between 380nm-700nm, sandwiched between the larger spectrum of non-visible electromagnetic energy. While this spectrum in its entirety includes radio, gamma, and the other non-visible wavelengths, plant and animal life rely on the non-visible spectra closest to both ends of visible light to thrive -- that being the ultraviolet energy closest to the 380nm (blue light wavelengths), and infrared energy closest to 750nm (red light wavelengths).
Metrics to define full spectrum lighting
Since sunlight varies in color temperature throughout the day - warmer during dawn/dusk, cooler and whiter throughout the daytime - there isn't an exact metric to measure full spectrum light bulbs by. So, while many like to define full spectrum as light in the "cooler" daylight white range (to mimic natural sunlight at midday), all variations of sunlight are still full spectrum and beneficial - they just have different effects!
That said, the following are two lighting metrics you should be aware of:
Color temperature is a measure used to describe a light source's visual appearance and whiteness. Most light bulbs range between warm white, natural white, and cool (daylight) white—the cooler a light source, the more blue light available in its spectrum. Conversely, the warmer a light source, the less blue light and more red light available. As we just mentioned, sunlight varies throughout the day in its spectral constitution - always full, but its color will vary between skewing more towards blue or more towards red.
Color Rendering Index (CRI) is a measure on a scale of 1 to 100 of how accurately a light source replicates colors as compared to natural sunlight (which has a CRI rating of 100). The higher the value, the more accurately colors appear.
Some uses for full spectrum lighting
Let's start with the most obvious and common use of full spectrum light, to offset and relieve symptoms of Seasonal Affective Disorder (SAD). When used in more therapeutic, concentrated bright light doses - through the use of dedicated lightboxes or light pads - it's known as bright light therapy. These light therapy units use either cool or daylight white LED or fluorescent lights to deliver stimulating doses of bright white light that our bodies perceive similarly to daylight, triggering our circadian rhythm and providing an uplifting, awakening effect.
To stimulate and trigger alertness
Similar to the above for SAD relief, but less concentrated. As we learned before, every color of the light spectrum has a corresponding wavelength and energetic effect. Blue light will be necessary to really create an awakening effect, as our eyes use the presence of blue light as an indication for the daytime release of cortisol and simultaneous suppression of melatonin, the sleep hormone.
This one is more of a catch-all, as enhanced well-being has different meanings for everyone. So, we'll just go with our belief on this one.
If you want the most out of your light, then you'll want to use a variety of lighting (in terms of light technology, color temperature, etc.). You'll see what we mean in a second.
Lighting technology, color, and energetic effects
How do we know if a light source has a full visible light spectrum or contains infrared and UV?
Unfortunately, on its own, it's hard to tell. But knowing a thing or two about lighting can help you to understand. It mostly comes down to light technology- whether a light source is incandescent, halogen, fluorescent, or LED.
Incandescent light sources are what we call "analog" light, and on their own produce full spectrum visible light, plus nourishing infrared energy (felt mostly as the heat thrown from these bulbs!). Its spectrum skews less towards blue, and more towards red, and looks more like sunlight at dawn/dusk. Since incandescent light has plenty of red wavelengths (and infrared!), these bulbs are wonderful to wind down, relax, and nourish yourself with. They don't have an energizing effect per se, but more of an "uplifting" effect (especially color-corrected versions like Chromalux®).
Halogen light is just an "enhanced" version of incandescent light, with a whole and full spectrum that skews just slightly more towards blue. The increased blue gives these bulbs a slightly more energizing effect than incandescent, while still possessing the same analog light benefits as incandescent.
Fluorescent light can be full spectrum (when it has a CRI over 96). While you can find warmer appearing fluorescents, most are available in daylight or cool white color temperatures between 5000K and 6500K. That means the visible light spectrum skews mostly towards blue wavelengths, and the light will have a very energizing effect. Certain full spectrum daylight fluorescents also dip into the ultraviolet range, and when specified as such, are excellent ways to provide birds and reptiles in captivity with UVB light to promote Vitamin D synthesis (the amount of UV produced isn't nearly enough to have any effect on humans).
LED light is the most commonly available and versatile light. Since it creates light through the use of digital diodes, the possibilities are endless in the types of light it can create! You can find virtually any color temperature in LED bulbs - warm white, natural white, and cool white, bulbs that can switch through all the different hues (smart light bulbs), and full spectrum varieties.
However, since it is a "digital" light source, we always recommend mixing it up with other more whole versions of light like incandescent or halogen to get the most out of your lighting.
One of our favorite light hacks is to use incandescents at close range in table, desk, and floor lamps, and color-corrected flood LED bulbs in any overhead fixtures. This is a great way to get the health benefits of incandescent with the energy efficiency of LED!
To Wrap Up
Remember, the best light is what feels best for you individually. Apart from specs on a specific light source, if you find something feels right, then go for it! We all perceive our surroundings and light differently.