Demystifying CCT in Lighting: Understanding Colour Temperatures
If you’ve seen “Cool white 4000K” printed on the box of a new lightbulb, did you know what it meant?
The “K” refers to Kelvin, which is a measure of temperature, like Celsius or Fahrenheit. Kelvin is the scientific option, as it’s very accurate, and is used to measure absolute zero; 0 Kelvin = -273 Celsius.
So, what does a temperature have to do with my lightbulb? Kelvin temperature is used to indicate the colour of the light. This has become necessary in the development of LED, as previously, with halogen and incandescent lamps, they were always simply warm white. Many fluorescent lamps were always cool white, and there wasn’t a lot of option on the matter. LEDs, however, allow so many options, that manufacturers need to communicate this to customers.
Cool white is 4000K, but warm white is 3000K – that doesn’t seem right. Higher temperature should be warmer, right? Well, no. Not in this case –
Even though this is a temperature scale, it’s a correlated colour temperature – that’s why it’s called CCT.
Let’s Take a Step Back First with an Example of Colour Temperatures.
If you light a fire, the flames are yellow, but the coals are red. The flames are hotter than the coals, so the colour is different. If you’ve ever seen a welding flame, this is often blue, or white. This is much hotter than your fire’s flames.
The explanation is this: the hotter an object (like a piece of coal) gets, the lighter the visual colour becomes. (red -> orange -> yellow –> white –> blue).
The shift of colours from the visually “warm” colours like red & orange, to the visually “cool” colours like blue and bright white, is why we consider a lamp with 5000K ratings to be cool, and a lamp with a 2700K rating, to be warm. The CCT rating refers to what an object (like your coals) would look like at that Kelvin temperature.
Harnessing the Power of Color Temperature for Productivity and Well-Being
Now that we understand why warm lamps are warm, and why cool lamps are cool – what to do with this knowledge?
These colours influence us as humans quite profoundly. If you’ve ever paid attention to it, you might notice that midday is bright and quite a “harsh” temperature (daylight is considered 5500K and up, although this is not why the sky is blue), and evenings are gentler and more warm.
Most people have more energy during the day than in the evening, and we often feel much more relaxed in candlelight than in office lighting. This is crucial, because if you’re using a lamp that simulates bright midday light in your bedroom, you can start tricking your brain and your body into thinking it’s not evening, and you can develop difficulty sleeping.
If you have an office or a laboratory with warm, dimmed lighting, your workers might be so relaxed they don’t get any work done, or they risk injury if they can’t see properly. The colour and intensity of the lights used in any space is critical to the success of that space. The study of this is called Human Centric Lighting and we will delve into that in another article.
Advice from Mask. Design
Mask. Design can assist your project with making these decisions, but our general guidelines are:
Use warmer colours in your home – especially in bedrooms and living spaces
In kitchens and bathrooms, you can opt for a more neutral light (4000K) as this is better for tasks, without distorting the colours of things around you.
Commercially, if you’re in a retail space, you can stay with 3000K or 4000K, depending on your brand and product.
Offices usually prefer a neutral to cool colour, as this keeps workers more alert. The same applies to warehouses and factories.
In hospitality, if you have a restaurant, we suggest warm and very warm colours, definitely dimmable, and bright, with cool to neutral colours in the kitchen for staff safety.
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