Light Bulb Colour Temperature

You’ve likely already noticed that some light bulbs emit a different colour than others - there are a number of reasons for this difference.

It’s not just the colour of a light bulb that can vary, but also the temperature. Do these two factors correlate somehow? Are they complementary to one another? If so, what causes both factors?

These questions and many more are answered throughout this article, so read on to find out more!

Colour temperature can also be called correlated colour temperature. This immediately suggests that colour and temperature correlate in some way or another.

Correlated colour temperature refers to a light’s appearance or tint, which varies massively between bulbs. Most emit white light but even this varies between cold and warm. You may think that all the white light bulbs look the same, however, the temperature difference causes a slightly different tint of white.

Light bulbs such as incandescent light bulbs tend to emit warmer colours while bulbs like LEDs emit cooler colours. That being said, each of these bulb types still have the capacity to be either warm or cool.

These different variables can interact in such a way that results in an almost endless number of combinations ranging between warm and cool.

Let’s take a look at how to measure and identify these differences.

We measure colour temperature in degrees Kelvin.

The scale ranges between 1,000 and 10,000. Interestingly, the warmer your bulb is, the lower its temperature will be.

Candlelight has the lowest colour temperature in degrees Kelvin, while the sun has the most. For a visual aid, take a look at this diagram:

As you can see, the various forms of colour temperature can be measured quite easily once you know the basic range of each grouping. Naturally, no light bulbs emit a colour temperature even close to pure sunlight.

However, you can measure your light bulb’s colour temperature based on the other average measurements here.

For example:

• If your light bulb is emitting a cool white glow, then you know it is likely somewhere between 4100K to 5000K.
• If your light bulb is emitting a soft white light, then it will fall somewhere between 2700K and 3500K.

In previous years, colour temperature wasn’t an issue. This was because we used incandescent light bulbs for every light in the house. Since all of our lights were the same, all we needed to worry about was the wattage of the bulbs we chose.

Now that energy-efficient light bulbs, such as LEDs and CFLs, are commonly used, the wattage level of our light bulbs doesn’t ensure that the light will emit the same colour temperature.

For example, if you swap out an incandescent light bulb at 60 watts for an LED at 60 watts, the LED will emit a much brighter, cooler colour temperature than the old incandescent light ever did.

Because this is the case, you would need to look for an LED with the same or a similar colour temperature to the old incandescent light bulb if you want it to light up the room in the same way.

Fortunately, this usually leaves you with an LED that has less wattage and consumes less electricity than the old light bulb ever did.

There’s no specific rule that forces you to use warm or cold lights in a certain environment. The easiest way to measure whether you want more warm or cold lights is based on the effects of each type.

Warm light tends to be relaxing and calming. It is best used in places where you want to rest and recover from the stresses of the day.

Cooler lights are better for creating a focussed environment. These are generally best used in a workplace or school.

Warm white light, which measures between 2000K to 3000K, is best for relaxing locations. These are some of the best rooms and places to install warm white lights:

• Bedrooms
• Bathrooms
• Dining and Living Rooms
• Outdoor Patios
• Restaurants

Cool white light, which measures between 3100K to 4500K, are better for when you need to focus. They’re best used for the following environments:

• Work Environments
• Kitchens
• Basements
• Attics
• Garages

If it's something more specific, it's always good to do some research or ask industry experts. For example, when it comes to lighting for wine cellars, we generally recommend it to use warm-colour temperature, dimmable LED lighting.

Cold lights just wouldn't give out the same desired effect.

Daylight bulbs, which measure between 4600K to 6500K, work in a similar way to the sun: these bulbs are dazzling and should not be used in places that you will remain in for long periods of time unless that location has no natural light in it whatsoever.

The garage or a basement are good examples of where daylight bulbs can be put to effect.

On the other hand, smaller daylight bulbs can be great for lighting up displays or even providing your home with security.

Floodlights are a great example of this: you can use them to make sure no one can get near your home undetected at night.

As you can see, colour temperature has more of an impact on the light bulbs we choose than you might have thought.

The next time you seek to change a light bulb and the new bulb is a different design, make sure you ask what the colour temperature is to determine if that bulb will be a good replacement in the chosen fixture!