Learn everything you need to know about the Kelvin scale and how you can use it to manipulate color temperature in your imagery.
The Kelvin scale measures the temperature of light. A must-know tool for photographers.
Read on to find out what the Kelvin scale is, how you can make use of this long-standing scientific technique, as well as a useful breakdown of each color temperature on the Kelvin scale’s range.
What Is the Kelvin Scale?
One of the three main ways that temperature is assessed, alongside Fahrenheit and Celsius, the Kelvin scale is a unit of temperature and color, invented by British scientist William Thomson—also known as Lord Kelvin—in 1848.
Most commonly used when we refer to the temperature of lighting (warm or cool, at its most basic), the scale is also a useful tool for photographers looking to have complete control over the color temperature of images.
From very warm, low Kelvin temperatures to the ultra-cool colors of blue sky light, the Kelvin scale is a useful measure of temperature in imagery. License these images via Theerasak Suksawang, K-Angle, metriognome, and Phoenixproduction.
In our coverage on three-point lighting, we briefly touched upon the properties of color temperature and how different light sources generate a color that is perceived as either warm or cold. The basis of how light temperature is measured is against a Kelvin scale.
Of course, when we hear the word kelvin, we typically think of one of the measurements to quantify heat, but it’s also a term used to measure the color “temperature” of light.
The idea is that you compare the color of the light source to that of a theoretical black body radiator when it’s heated. What does that mean? Well, when a substance is heated, it also emits light. And, how much that object is heated determines the color makeup of that light—think the hotter a flame, the more it burns from red to blue.
What Is the Range of the Kelvin Scale?
The Kelvin scale ranges from 1000 to 10,000, measured in kelvin (k). A low kelvin number indicates a warmer color temperature (red/orange), while a higher kelvin number refers to a cooler color temperature (white/blue).
While the Kelvin scale runs from 1000 to 10,000k, typically the numbers we would often see crop up in lights pertaining to filmmaking and photography would be found within the following bands of kelvin:
- 2000k-3000k for the warm white and yellow glow of flames and household bulbs.
- 3000k-4500k for tungsten lights and the early and late parts of the day.
- 4600k-6500k for direct sunlight, overcast skies, and HMI lights.
While these three bands are the most commonly used in photography, there is a full range of kelvin temperatures to explore.
Below, discover how you can bring warm coziness to your indoor shoots or cool dramatic light to outdoor landscapes by using a wide range of Kelvin scale values.
We’ll walk through:
- Extremely warm light
- Very warm light
- Warm light
- Warm white light
- Relatively warm white light
- White light
- Relatively cool white light
- Cool white light
- Day white light
- Very cool white light
- Blue sky light
Each of these categories of color temperature can be quantified with a particular kelvin value, and can be adjusted on camera equipment to compensate for varying temperatures.
For example, if you shoot a subject in cool midday light, you can set the Kelvin scale on your camera to match the light conditions you’re shooting in. By doing this, your camera will know which color tones to highlight or downplay, allowing you to further experiment with, say, bringing in beautiful warmth to an otherwise cool image.
Extremely Warm Light: 1000k-1900k
The bottom of the Kelvin scale would denote black, so we need to travel slightly forward along the scale to begin. At 1900k, we hit our first visual representation of color temperature with a candle flame. Candle flames and fire typically sit at 1900 kelvin and will produce a warm orange or red glow.
A note of caution when working with extremely warm light. One hour after sunset is usually defined at 3500k but, depending on the weather, it could also be 3400k or 3700k. Some cameras denote the daylight color balance as 5000k, and others use 5600k.
With this in mind, it is wise to experiment with your own camera’s settings in different light conditions and at different times of day.
Some cameras will also have automated settings that don’t always produce the best results in extremely warm light. You may find yourself reaching for that white balance setting on your camera to switch the color balance to that of the light source.
If you do a gray card reading next to a lit candle, your camera will see the orange flame as overly warm and introduce blue to negate the orange, turning the light white in your photo.
Of course, candles don’t emit white light, so you may want to be wary of this when photographing in these tricky lighting settings.
Very Warm Light: 2000k-2500k
As we move from the fiery warmth of 1900k, we head into the 2000k-2500k region. This Kelvin scale band produces colors often seen on a daily basis and are generally described as warm white. Street lights are usually set at 2000k because the warmer light is calming and easy on the eyes.
If you’re an early bird or night owl, you may be familiar with the warm light that casts everything in a beautiful glow just after sunset or sunrise. This too is typically around 2000k.
However, this is not to be confused with Golden Hour. This light is typically the first or final light seen before the sun passes the horizon.
Warm Light: 2800k-2900k
At 2800k-2900k, we find ourselves at a color temperature commonly found in household lighting. Most lamps, ceiling lights, and other indoor lighting will sit at 2800k-2900k.
In photography and filmmaking, this subtle warm light is often used to replicate the cozy feeling of lived-in, indoor environments.
Warm White Light: 3200k
As we move up the Kelvin scale, we start to reach some of the most commonly used temperatures in photography. One of these would be around 3200k, a warm white light that is flattering, soft, and neutral, making it a good Kelvin temperature for shooting studio photography.
This measurement is also the color temperature you find in the halogen bulbs housed in Fresnel lamps.
Relatively Warm White Light: 3000k-3500k
The favorite time of day for most photographers and filmmakers to shoot is undoubtedly Golden Hour. With a Kelvin scale range of 3000-3500k, this window of time just after sunrise and just before sunset allows blue light to disperse, leaving a gorgeous golden light spread across the landscape.
A top tip for shooting in Golden Hour conditions is to avoid setting your white balance to calibrate for this light as, by doing this, you would lose the golden touch in your images.
White Light: 3500-4000k
From 3000k to 3500k on the Kelvin scale, we’re nearing the region where temperatures are no longer warm white and are instead referred to as bright white. Sometimes, at a higher Kelvin value of 4000k, the temperature can be referred to as neutral white.
Fluorescent lights fall into a temperature bracket between 3500k and 4300k, sitting determinedly in the middle of the Kelvin scale, and appearing neither warm nor cool.
You can find this color temperature in the lights used in professional kitchens, retail stores, and daytime offices.
In these workplace settings, colors need to appear natural and neutral but, for photography, this Kelvin scale temperature can be tricky to work with, as it lacks depth and mood.
Relatively Cool White Light: 4100k
The Kelvin scale can be somewhat paradoxical at times (with the sun leaning more towards a cold color despite being the hottest element on the list), and moonlight is no different. The Kelvin scale measurement of moonlight is 4100k, which on the scale is actually warmer than sunlight, even though we typically think of moonlight as cold light.
Psst . . . If you’re interested in the science behind this, discover this in-depth conversation on the subject of temperatures of both moonlight and sunlight on the Physics Stack Exchange.
Cool White Light: 4500-5000k
In the early morning and late afternoon, the sun has yet to reach its peak position, but it’s also not as horizontal as it is during sunrise and sunset. As such, we receive a warmer and less harsh light than the midday light, but not as golden as the setting sun. You will find this light measured from 4500k to 5000k.
There is also a secondary light that we typically find at 5000k-5500k, which is the cool white light of a camera flash.
Day White Light: 5600k
Moving even further up the Kelvin scale, we reach our second primary color temperature, 5600k. This is regarded as the default daylight color temperature of a high midday sun with no cloud cover.
Often, when we think about specific color temperature, the color we see is that of how we perceive that color under daylight. As such, daylight is often the base correction temperature when trying to correct abnormal color casts from stray light sources.
Many consumer and professional LED lights will ship with either daylight or bi-color based LEDs to aid in this correction process. If your camera (or film) is daylight balanced, this light will appear as white.
Very Cool White Light: 6500k-7000k
On the Kelvin scale, 7000k appears almost abnormally blue to be seen in the real world. However, that color measurement is indeed the color of daylight when the sunlight’s waves are dispersed through a heavy set of cloud cover.
Think of an overcast winter day in the afternoon—this very cool white light is not the most flattering of light temperatures in which to photograph human subjects, but it can bring a brooding, moody atmosphere to cityscapes or landscapes.
Blue Sky Light: 9000k-10,000k
The highest values on the Kelvin scale are often a source of confusion, and rightly so.
9000k (and onward up to 20,000k) is attributed to a clear blue sky. However, when one thinks of a blue sky, you are probably going to think of sunlight. You’re not going to get a blue sky without daylight, right?
While that’s true, when photographing or filming elements directly under a clear blue sky, you may find it throws a cast over your image even though everything looks as it should be.
For example, in this photograph of Lake Garda (above), which was shot at a daylight color balance of 5600k, it’s a sunny summer’s day. Initially, nothing seems inherently wrong.
However, when I increase the white balance to 9000k (above), this counters the blueness with warm attributes and corrects the image. All of a sudden, the top image appears much colder than before, and the bottom image feels sunnier and more inviting.
Striking the Right Color Balance with the Kelvin Scale
The Kelvin scale may have been invented to measure temperature scientifically, but it’s an indispensable tool for photographers, filmmakers, and image editors.
By using your knowledge of warm and cool Kelvin temperatures, you can create images that strike exactly the right color balance, preserving the perfect mood and clarity in your photographs.
Eager to learn more about how to light your photoshoots? Make these your next read:
License this cover image via Phoenix Production.