How To Tell If A Bulb Is Full-Spectrum?

You’ve possibly heard so much about full-spectrum bulbs, their usefulness, and the health benefits they hold for users.

However, the term, “full-spectrum” is a mere marketing term and not a scientific term.

This means that any bulb manufacturer can label a non-full-spectrum bulb as being full-spectrum while you may also end up buying a full-spectrum lamp without the “full-spectrum” label.

All these emphasize the importance of knowing if a bulb is full-spectrum or not. This post will guide you to know if a bulb is full-spectrum or not. Read on.

How to Know a Full-Spectrum Bulb?

A full-spectrum bulb can produce the full range of the color spectrum i.e. it produces both the invisible and visible color wavelengths of light.

Hence, a full-spectrum bulb represents the entire visible light spectrum just like the sun.

As a result, a full-spectrum bulb offers the closest alternative to natural daylight (sunlight) and offers similar health and well-being benefits as those gained from exposure to natural daylight.

Two metrics are always used to measure light. The first is color temperature, which is measured with the Kelvin color temperature scaleand the second is the Color Rendering Index (CRI).  

Kelvin– this is the method of describing the color characteristics of light, and it refers to the appearance of the color of the light.

Both the sun and Indoor Sunshine® are rated 5500K on the Kelvin Color Temperature Scale.

The yellow-orange glow of a traditional tungsten bulb is rated about 2700K but as the light becomes colder and whiter, its rating increases to about 6500K on the Kelvin score.

CRI – the Color Rendering Index describes how the colors appear under man-made light compared to natural sunlight.

CRI is measured in percentage, the higher the percentage, the better the color rendering. Sunlight has 100CRI, while Indoor Sunshine® light has 95CRI.

Typical CRI and Kelvin ratings are:

  • 49CRI 2800K         Incandescent
  • 56CRI 3000K         Warm white fluorescent light
  • 68CRI 4200K         Standard cool white fluorescent light
  • 90CRI 5000K         Daylight fluorescent light
  • 93-95CRI 5500K    Indoor Sunshine®
  • 100CRI 5500K       Outdoor Sunshine

Generally, full-spectrum bulbs have a color temperature of about 6500K and a CRI of 96% (although a perfectly full-spectrum bulb has 100CRI).

Hence, when compared to daylight bulbs, full-spectrum bulbs can give a brighter and whiter light, even with better color rendering.

So, whenever you need to tell if a bulb is truly a full-spectrum bulb, simply look at color temperature and CRI rating.

Based on what is expected of a full-spectrum bulb, a full-spectrum bulb should deliver frequencies of light from 380nm to about 760nm.

According to Graf, bulb manufacturers should include a SED/SPD chart on the product packaging so that buyers can examine the frequency the bulb produces.

With the SED/SPD chart, you should be able to tell if a bulb is full-spectrum or not.

You would even be able to see that a lamp without the “full-spectrum” label would give frequencies just as bulbs marked with the “full-spectrum” label.

Though this is not a major factor to tell if a bulb is full-spectrum, it may still work for identifying full-spectrum bulbs. Full-spectrum bulbs are often priced higher than non-full-spectrum bulbs.

Typically, full-spectrum bulbs are priced about four to 12 times higher than bulbs that are not labeled “full-spectrum.”

The increase in the price of full-spectrum lamps is usually due to claims made by full-spectrum bulb manufacturers about the bulbs: greater productivity, improved health, enhanced color perception, and better visibility.

In conclusion, all full-spectrum lamps have a color temperature that is greater than or at least 5,500K and a CRI of at least 90.

Whether or not they’re labeled as “full-spectrum” depends on the bulb maker.

Difference Between a Full-Spectrum Bulb and Daylight Bulb

When choosing the type of light that is the most suitable for your needs, you need to be aware of the differences between full-spectrum and daylight bulbs.

Contributing to the confusion among consumers is the fact that the “fullness” of a light spectrum is not directly observable to the human eye.

That is, a full-spectrum bulb and a non-full-spectrum bulb may have the same emitted light appearance and color though they have significantly different spectral properties. So, one could ask why full-spectrum lights are important.

A standard daylight bulb is sufficient if you need a bulb that gives the appearance of daylight for creating an airy-feeling officeor brightening a reception area.

Daylight bulbs are available in an extensive range of styles – from energy-efficient LED tubes and panels, through to low energy spiral daylight bulbs and classic incandescent GLS daylight bulbs.

However, if you want a sunlight kind of lighting to light a windowless room, to address SAD (Seasonal Affective Disorder) issue, or you need to get the perfect color rendition for visual tasks like sewing and designing, then the full-spectrum bulbs are your best option.

Although daylight bulbs provide similar lighting levels to full-spectrum bulbs as the color may be indistinguishable, there are some benefits that full-spectrum light offers over daylight. These benefits are:

Improved Color Rendition

Color rendition has to do with the way objects appear under the light source. Full-spectrum light offers a better color rendition than daylight.

For instance, when a daylight bulb is shown onto a red apple, the emitted light color may match that of natural daylight; the appearance of the red apple would be very different compared to the appearance under full-spectrum light.

Daylight lacks red colors in its spectrum. Hence, there is a lack of red light energy reflecting off of the apple, making the red apple appear dull.

On the other hand, full-spectrum light has red colors in its spectrum and would make the red apple appear brighter.

Due to their ability to improve color rendition, full-spectrum bulbs are indispensable for applications that require consistent and accurate color appearance, especially for those working in graphic arts, photography, and artwork, etc. as inaccuracies in color perceptions may hinder their work.

Improved Health or Biological Benefits

Full-spectrum light also offers some health benefits, which are not directly related to the way we see color or light. The health benefits of full-spectrum light are related to other biological processes.

For instance, some hormones and pigments in the body react to various wavelengths and intensities of light and are affected by full-spectrum light.

The effect of full-spectrum light on these pigments and hormones can regulate our overall moods and signal our body to promote sleepiness and alertness.

The biological benefits are not limited to human beings alone. Plants also rely on light energy and react differently to different light spectrums.

Depending on the light spectrum exposed to, a plant may perform photosynthesis more efficiently, or experience improved flowering and fruit production over vegetative growth.

Though it hasn’t been generally confirmed, several medical studies and research have observed that a lack of exposure to full-spectrum light (natural daylight) may be detrimental to human health.

Exposure to an adequate supply of full-spectrum through natural daylight may not be possible for some people due to factors which include their geographic location, location of their home, workspace design, work shift scheduling, etc.

Nevertheless, using a full-spectrum bulb can imitate the natural daylight and mitigate the effects of lack of exposure to full-spectrum light through natural daylight.

Though the artificial full-spectrum light sources will certainly fall short of imitating natural daylight100%, they will to a certain degree play an effective and significant role close to natural daylight.


As lighting technologies began to experience rapid development, more full-spectrum lighting options are made available to consumers with some bulbs carrying the “full-spectrum” label.

However, how can one tell if a bulb is truly full-spectrum?

Full-spectrum light is a bit challenging to fully understand because full-spectrum light is not directly visible to human eyes.

As a result, some dishonest lighting companies are using deceptive marketing strategies to label their bulbs as full-spectrum bulbs though their bulbs do not give the color rendition and accuracy, and health and biological benefits that a true full-spectrum bulb gives.

To tell if a bulb is full-spectrum, color rendering index (CRI) and color temperature in Kelvin are the universally accepted metrics.

So, always remember these two metrics to accurately compare and differentiate a full-spectrum lamp from daylight or fluorescent bulb.

Ideally, a full-spectrum bulb should have a color rendering index of 95 or higher and a color temperature of 6500K.