Light Reading: Colour Temperature
You may have noticed there is likely a visual difference between the light coming from your garage and the light coming from your dining room chandelier. The difference is in the temperature of the light. But what does that mean exactly?
History
We’ll start at the beginning. Colour temperature was first explored in the late 1800s, when the British physicist William Kelvin heated a block of carbon. He observed as the block changed colour as it heated up, going from a dim red, through various shades of yellow, all the way up to a bright bluish white at its highest temperature. The resulting measurement scale for colour was named after Kelvin.
Kelvin Scale
Colour temperature is now the way we describe the appearance of light. You’re probably familiar with terms like “cool white” and “warm white” lighting, like those you’ve seen on a standard light bulbs, but most bulbs are also labelled with their degrees in Kelvin. Kelvin (K) typically ranges on a scale of 1000, to 10000. The colour temperature of a bulb gives us an idea of what the look and feel of the light produced will be, if it has a low Kelvin it’s warmer, and the higher up the scale it goes, the cooler the light produced will be. Typically, bulbs with a colour temperature between 2000-3000K give off a warm white glow. Between, 3100-4500K are more of a cool white, and 4600-6500K give off light similar to daylight.
Keep in mind the use of the terms “warm” and “cool” is a bit of a contradiction because when examining the Kelvin scale, you’ll see the “cool” light is actually hotter than “warm” light. The terms aren’t intended to describe the actual temperature of the light but rather the resulting aesthetic.
See the below image to compare Kelvins to their corresponding colour temperature:
How to Measure
Colour temperature can be easily measured simply using a handheld meter where a reading can be taken in seconds with the press of a button. You must take into consideration that the scanner must be held close to the light source or where the colour is the most average (such as in the middle of a room) in order to get an accurate reading.
What Colour Temperature Should I Use?
So how do you know what colour temperature works best for your space? Should your lighting temperature be different for your bed side table and in your office? Ultimately, it depends on the viewer’s desired appearance and feel that they’re going for. Typically, lighting on the warmer side is preferred for bedrooms, bathrooms, restaurant/commercial ambiance lighting, and decorative outdoor lighting. Whereas lighting that’s on the cool end is best for task lighting, security lighting, display areas, and garages.