TrueDark Kelvin Color Temperature: What You Need to Know

Kelvin Color Temperature: What You Need to Know


Lighting—it’s all about color temperature, lumens and lux.  Why? Because these measures of light not only affect the atmosphere of a room; they can also impact a person’s energy level, mental clarity, and well-being while inhabiting that space.

What Is Color Temperature?

This refers to the warmth or coolness of a light source, measured in Kelvins (K). This measurement is based on an absolute scale, which means that it starts at zero and continues to increase. 

Lower temperature bulbs (1,000–3,000K) produce warm, soft white light  like that of candlelight, ambient sunsets, or standard incandescent bulbs. 

Medium temperature bulbs (3200–4500K) produce neutral white light that creates a bright and inviting ambiance.  

Higher temperature bulbs (5000–10,000K) produce cool white light.  Color temperatures in this range are closest to the appearance of daylight. This range of light is often described as “clinical” because it makes objects appear crisp and vibrant. 

In short, the higher the Kelvin rating (expressed in K), the whiter the light will appear. For a more in-depth look at light sources and color temperature, reference the chart below:

How to Interpret Kelvin Color Temperature Vs. Colors

While kelvin follows an absolute scale, human vision can perceive many colors that exist outside of this spectrum.  Color is the appearance of an object with respect to the wavelengths of light that are reflecting off of it. This attribute is determined visually by hue, saturation, and brightness of the light reflected off of an object.  With that said, it’s common practice for businesses to use the CIE 1931 color spaces to identify specific colors. Rather than describing how colors appear to humans, this Color Matching System helps users numerically specify a measured color and accurately reproduce it (e.g. in print or illuminated displays).

There is no true conversion of nanometers to kelvin. However, within the CIE color spaces shown above, you can also see the Kelvin scale (the curved black line in the center of the spectrum).  Modern lighting technology will often produce vibrant colors which are way off the Kelvin line.  Note that any light that does not fall on this line can be classified as a (numerical) color but not a Kelvin. 

Color Temperature and Your Circadian Rhythm

Research shows that light is one of the most influential inputs on your circadian rhythm. It enters the eyes through special receptors that are especially sensitive to blue light, which provides humans with precise blueprints for carrying out important biological functions over the course of 24 hours (e.g. waking up, eating, exercising and sleeping).  So, when it comes to regulating your sleep/wake cycle, the saying, ”timing is everything” should really also acknowledge color temperature.

Now think about a typical 24-hour period. As the sun gradually changes its position in the sky, the light color temperature transforms from warm to cool, and back to warm again.  These natural phases of sunlight are naturally programmed into our biology, so when choosing lightingbe sure to consider the light sources that support your mood, energy, and natural sleep/wake cycle. 

Ideally, you want to incorporate “circadian” lighting in your home or office that mimics the color temperature of the sun’s natural light as it progresses throughout the day. For example, higher temperature bulbs are ideal for midday use because they help stimulate alertness and may assist with maintaining your energy and focus. So, while you’re working on specific tasks, it makes sense to use vibrant, invigorating light.  Lower temperature bulbs are conducive for illuminating spaces after sunset, especially if you want to create a more romantic setting or prepare your body to fall and stay asleep. In short, cool bright lights promote wakefulness and warmer lights encourage restfulness. 

For continued reading, be sure to check out Lumens and Lux: What You Need to Know 

Junk Light, Disrupted Sleep, and Your Health

Exposure melatonin disrupting junk light can have have effects on many aspects of your health

Sleep cycle disruption

Junk light exposure when traveling can disrupt your circadian rhythm. Long-term exposure to light at night which accompanies shift work is listed as a probable carcinogen by the World Health Organization. Light at night has shown to be highly associated with significantly the risk of hormone specific such as cancers of the breast and prostate.


The flickering wavelength of light associated with LEDs and compact fluorescent lights emit blue light that inhibits melatonin production but also create a unique glare that impacts your retina causing eye strain, headaches, and physical and mental fatigue.

Weight Gain

Red light and darkness move leptin and ghrelin into patterns that are (context dependent) associated with less hunger, while blue light does the opposite and can move both into patterns associated with more hunger.

Anxiety/Depression & Depression

Increase in cortisol, the stress hormone, due to circadian disruption. Memory recall is impaired with consistent sleep deprivation and may leave you distracted and not performing your absolute best.

The Importance of Melanopsin Cells

The Key to Better Sleep

detects blue light

The melanopsin cells detect blue light it tells your brain that it is “daytime” and less melatonin is produced.

sending signals to your brain

The signals to your brain to alert brightness and for the brain to increase or suppress the sleep hormone, melatonin.

Light Source

Melanopsin cells can’t differentiate the blue light that occurs naturally form the sun from the junk light emitted from your computer monitor.

Start Optimizing Your Life

Harness Your Biology to Fight Junk Light

Your body requires some blue light at the right time of day and from the right sources. That’s why we created TrueDark® Sleep Technology that gives you 24-protection from junk light day and night.

Use TrueDark® Twilights When You’re Ready for Sleep

Stop Junk Light with patented TrueDark® Twilights technology that frees your hormones and neurotransmitters to do their best work.

When the sun goes down, blue light isn’t the only junk light that can disrupt our sleep cycle and more than blue blockers are needed. Patented TrueDark® Twilights is the first and only solution that is designed to work with melanopsin, a protein in your eyes responsible for absorbing light and sending sleep/wake signals to your brain. Without melanopsin, melatonin can’t be accessed.

When you wear your Twilights for as little as 30 min before bed you prevent your melanopsin from detecting the wrong wavelengths of light at the wrong time of day. This supports  your circadian rhythm and helps you fall asleep faster and get more restorative and restful sleep.

glasses to help with computer eye strain computer glasses

TrueDark® Daylights for Your Waking Hours

The highly advanced lenses in TrueDark® Daylights operate on a more advanced level than traditional blue blockers.

Blue light emitted from the sun helps regulate our sleep/wake cycle. However, in today’s world, we’re exposed to an overabundance of blue light, or junk light from artificial light. This includes hours spent in front of  TVs, phones, and computers. It also includes time spent in artificial man made light with LEDs and fluorescent lights. Even if we’re simply reading a book, we’re doing that in artificial light which emit dramatically more blue light than the sun. That overexposure to junk light during the day has a dramatic impact on our neurotransmitters and hormones that are responsible for quality sleep.

The Only 24-hour Solution for Your Eyes

Increase Your Mental and Physical Performance

Translate »