Everything You Need to Know About Full Spectrum Lighting

The term "full spectrum light" gets used frequently, and oftentimes erroneously, as there is no single agreed upon definition.

There are no cut and dry definitions that draw the line between "full spectrum" and "not full spectrum." This makes evaluating and comparing full spectrum bulbs challenging for consumers, and has led to numerous manufacturers and brands making dubious marketing claims that their bulbs are "full spectrum" despite serious deficiencies in the spectral content of their lamps.

For the purposes of this discussion, as well as our internal quality control and specifications at Waveform Lighting, we define full spectrum light as:

A light whose spectrum closely mimics that of natural daylight. Specifically, it should have a CRI (Color Rendering Index) of 95 or better, and a color temperature of 6500K.

Read below for a basic overview of what full spectrum lighting is, the benefits of full spectrum light, and how to quantify and compare full spectrum bulbs.

 

What is full spectrum light? Full spectrum is not directly visible or observable

Contributing to the confusion among consumers is the fact that the "fullness" of a light spectrum is not directly observable to the human eye. In other words, a non-full spectrum bulb and natural daylight could have the exact same emitted light color and appearance, despite having significantly different spectral properties.

Full spectrum typically refers to the completeness of a light source's spectral energy, particularly when compared to natural light sources such as natural daylight. The exact spectral composition of a light source can only be determined by specialized photometric equipment, such as a spectrometer.

In other words, as a consumer, you have no practical way to independently verify or confirm that a full spectrum bulb you purchased actually has a complete spectrum.

How can that be?

Spectral speaking, there are many ways to create the same light color, and this also holds true for the color of natural daylight (commonly called daylight white).

For starters, let's take a look at the light spectrum for natural daylight. You will notice that the light energy is distributed evenly across the entire visible spectrum, without any gaps, dips, or spikes.

Next, we take a look at the light spectrum for a daylight fluorescent lamp. Notice that despite its daylight color rating and emitted light color, the spectrum is very different from natural daylight. Specifically, there are numerous spikes and "valleys" as well as very little light energy emitted in the red wavelengths.

What is very important to remember is that both natural daylight and this fluorescent lamp have the same apparent light color - daylight white. In other words, despite a significant spectral difference, the light color emitted from the fluorescent lamp is indistinguishable from daylight, to our eyes.

 

If the color is indistinguishable, then what's the point of full spectrum light?

Broadly speaking, full spectrum light has two primary benefits:

1) Improved color rendition

Color rendition is concerned with the way objects' colors appear under the light source. In our example above with the daylight white fluorescent lamp, even though the emitted light color (daylight white) matches that of natural daylight, the fluorescent light shining onto a red apple, for example, would appear very different compared to natural daylight.

The reason is that objects' colors are determined by the wavelengths they reflect. Since the fluorescent lamp lacks red colors in its spectrum, there is a lack of red light energy reflecting off of the apple, giving it a dull red color instead.

As such, full spectrum light sources are indispensable for applications requiring accurate or consistent color appearance. For example, workers in artwork, photography and graphic arts all require full spectrum light sources so that inaccuracies in color perceptions do not hinder their work.

Read more about high CRI and how the Color Rendering Index works.

2) Improved health or biological benefits

The health benefits of full spectrum lighting are not directly related to the way we see light or color. Instead, it relates to other biological processes, such as the way pigments and hormones such as melanopsin in the human body react to various wavelengths and intensities of light. These processes  are not directly related to the vision system, but instead provide signals to our bodies to promote alertness, sleepiness and regulate our overall moods.

These processes are not limited to humans. Plants, who also rely on light energy, will also react to different light spectra differently. Depending on the spectrum of a light source, a plant may perform photosynthesis more efficiently, or promote flowering or fruit production over vegetative growth.

Medical research in this area is ongoing, but many studies have observed that a lack of exposure to natural daylight can be detrimental to human health.

Access to natural daylight is unfortunately not possible for many people, whether it is due to their geographic location, workspace design and/or shift scheduling, or the architecture or location of their home.

Full spectrum light attempts to mitigate the effects of lacking natural daylight exposure. Artificial light sources will inevitably fall short of 100% replicating natural daylight, but the degree to which a full spectrum light source comes close to natural daylight plays a significant role in determining its effectiveness.

 

How do we measure "fullness" of spectrum?

At its core, full spectrum light is one that approximates natural daylight at a spectral level. It is only with this spectral similarity that a light source can effectively deliver the benefits of full spectrum lighting.

Unfortunately, accurately assessing spectral similarity is not practical, and we can only make general observations (like we did comparing fluorescent and natural daylight, above). Is there a better way to quickly compare how full a spectrum is, and how close it comes to natural daylight?

Absolutely! Color temperature and color rendering are two critical metrics that help determine a light source's similarity to natural daylight.

First, color temperature tells us about the emitted light color of a light source, and is represented by "temperature" value that describes the relative balance between yellow and blue. The higher the temperature, the bluer a light source is, and the lower the temperature, the yellower the light source.

An incandescent bulb has a color temperature rating of 2700K. Unfortunately, this is too yellow and different from natural daylight, and as a result, will not offer the benefits of full spectrum lighting. The same applies to fluorescent and LED lamps that have a "warm white" color temperature of 2700K or 3000K.

Natural daylight, on the other hand, has a color temperature rating of 6500K. Therefore, in order to match the light color of natural daylight, a full spectrum light bulb should have a color temperature of 6500K as well.

In some cases, you may prefer a 5000K color temperature bulb. 5000K will be quite similar to 6500K, and offer similar benefits, but will not be a true match with natural daylight.

Second, color rendering index (CRI) tells us about the way colors appear under a light source, and more generally, about the quality of its spectrum. CRI is measured as a score with 100 being the maximum possible score. Natural daylight itself has a CRI value of 100.

A light source with a low CRI value will generally display (or "render") colors inaccurately, when compared to natural daylight. The reason for this discrepancy is in its spectrum, which results in apparent color discrepancies. A high CRI light source, on the other hand, will display colors very similarly to natural daylight, owing to its complete, balanced and full spectrum.

When searching for a full spectrum light, we recommend a light source with a CRI of 95 or above. As a bonus, look for a light source that also publishes its R9 rating - typically 80 or above would indicate a high quality spectrum.

 

Bottom Line

With the rapid development of various lighting technologies including fluorescent and now LED lamps, more full spectrum lighting options are becoming available to consumers.

Full spectrum lighting is somewhat challenging to fully grasp owing to the fact that it is not directly visible or observable. As a result, less-than-honest companies have and continue to use deceptive marketing to label their products as "full spectrum" - despite the fact that their products do not provide the color accuracy and biological benefits that a true full spectrum light source would.

Color temperature (CCT) and color rendering (CRI) are universally accepted metrics for lighting. To accurately quantify and compare full spectrum lights, remember to use these two metrics to make meaningful comparisons. Ideally, the light source should have a 6500K color temperature, and a CRI rating of 95 or higher.

Have more questions about full spectrum lighting? Learn more about Waveform Lighting's full spectrum lighting technologies, or contact us today!