What is Colour Temperature?

What is Colour Temperature?

The term colour temperature refers to the scale that is used to measure how warm/cool a light is – cool being blue and warm being yellow. This temperature is measured in Kelvins (K) and the lower the K, the warmer it is.

It is important to match the colour temperature of bulbs lighting up the same area. For example, you don’t want half your kitchen bulbs to be cool/blue and the other half to be warm/yellow. Colour temperature has a huge effect on the atmosphere of a room.

Kelvin Scale 

Your standard candle gives off a colour temperature of around 1000K, which is why it appears very warm and light. However, the blue light up in the sky comes in at around 9000K, which is why it is so cool and blue. The temperature of a light should be clearly shown on the bulb packet – but this is different to the brightness value.

What to do if you don’t know the colour temperature 

The Kelvin scale is endless but there are a few set colour temperatures that bulbs are designed to, making it easier to find replacements. The Kelvin value should be written on the packaging but, if it isn’t, you can use a light guide to match it. You should also be able to find colour temperature tables online.

2700K to 3000K – Warm White 

The traditional light bulb falls between these values, making it one of the most common colours. This creates a warm, yellow glow that lights up a whole room without being too blinding. It is perfect for relaxing rooms such as bedrooms and living rooms.

3500K – White 

These fall somewhere between warm and cool white. These are often used in offices, schools, receptions and other busy day-time rooms.

4000K – Cool White 

This light is crisp and clear, without any kind of warm yellow glow. Therefore, it is often used in kitchens, workplaces and other environments where stimulation is needed. They can also be found in bathrooms and outside floodlights due to the clear and bright nature of the light.

6500K – Daylight 

You may have seen bulbs advertised as ‘daylight bulbs’ and that is because the 6500K plus colour temperature is designed to mimic the natural outdoor light – although only on an overcast day. This is not sunlight! These are often used in outside lighting and can come off a little blue, hence why they are not used in relaxing, indoor locations. The only time they are really used indoors is for colour reproduction, such as in retail/display settings. These are different from full-spectrum daylight bulbs as these create light across the entire spectrum.

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