Deep Dive into Colour Temperature & CRI
When thinking about lighting, brightness is often the first factor that springs to mind. However, there are two technical factors that get overlooked and have a far greater impact, those being colour temperature and Colour Rendering Index (CRI).
Colour temperature describes the visual appearance of light, specifically whether it looks warm, neutral or cool. Colour temperature is measured in Kelvin (K) and is based on the colour of light emitted by a theoretical black body as it heats up. Lower temperatures emit a warmer, yellow light, whereas higher temperatures emit cooler, blue light.
The colour temperature of your light can have a huge impact on your space, for example, 2200-2700k low temperature lights are best used in living room areas or bedrooms where bright task lighting is unnecessary. Whereas 3000k lights that emit a slightly cooler colour temperature are best placed in areas that require bright task lighting such as kitchens or bathrooms.
Furthermore, colour temperature can affect our circadian rhythm which is the body’s internal clock that regulates our sleep-wake cycle, hormone release, metabolism and body temperature. It is driven by the suprachiasmatic nucleus responding to light or darkness, these cycles determine when we feel alert or tired. The colour temperature of lighting can work with or against our natural circadian rhythm, cooler white light resembles midday sun which stimulates feelings of alertness. In contrast, warmer white light helps the brain switch off as it replicates sunsets and dusk.
Colour rendering index or as we will refer to it, CRI, measures how accurately a light source reveals colours compared to natural daylight. This is expressed as a value between 0 and 100, for perfect colour accuracy this number needs to be as close to 100 as possible. Lower CRI values can cause colours to look distorted.
If the light source has a CRI rating of 70 or below the colour accuracy is considered poor, these lights are often found in carparks or on streets. A higher rating of 80-85 is considered good and these lights are typically found in residential properties or used in commercial spaces. A rating of 90+ means that colour accuracy is excellent, these lights are often used in spaces where colours must be accurate and true to life, such as art galleries, retail shops and restaurants kitchens.
CRI is a crucial factor that people often overlook, it affects how people and objects appear under artificial light. Depending on the CRI rating, skin tones can look natural or lifeless, and foods can appear vibrant or dull. Low CRI lighting often results in spaces that feel flat or uncomfortable, even if the colour temperature is technically correct. CTA – Whether you’re lighting one room or an entire home, the right choice comes down to two things: colour temperature and CRI. Get these right and you’ll transform how your space looks, feels, and functions.
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