Colour temperature is measured in Kelvin (K) and describes the visual warmth or coolness of white light. It affects mood, productivity, circadian rhythm, and how materials and finishes appear in a space. Choosing the wrong colour temperature undermines the entire design intent.
The Kelvin Scale for Lighting
Lower Kelvin values produce warmer, more amber light. Higher values produce cooler, bluer light. This is counterintuitive. "Warm" light has a low colour temperature. "Cool" light has a high colour temperature.
The scale originates from heating a theoretical black body. At 2700K, the black body glows a warm amber. At 6500K, it appears blue-white, similar to overcast daylight.
2700K: Warm Residential
2700K closely matches traditional incandescent bulbs. It creates relaxed, intimate atmospheres. Ideal for hotel rooms, restaurants, residential living spaces, and anywhere guests or occupants should feel comfortable and at ease.
Warm light enhances wood tones, earthy colours, and warm-toned fabrics. It suppresses blues and greens slightly.
3000K: Warm Professional
3000K is the most versatile commercial colour temperature. It provides warmth without the amber cast of 2700K. It works in retail, hospitality lobbies, high-end offices, and residential kitchens.
Many lighting designers default to 3000K for commercial hospitality. It flatters skin tones, renders materials accurately, and creates a welcoming professional environment.
3500K: Transitional
3500K sits between warm and neutral. It suits healthcare waiting areas, educational spaces, and offices where a balance between warmth and alertness is needed. It renders colours accurately without the coolness of 4000K.
This temperature is less commonly specified in the UK market but remains popular in North America and Australia.
4000K: Neutral White
4000K is the standard for commercial offices, retail, and task lighting. It promotes alertness and concentration. Colours appear natural and accurate under 4000K light.
Office lighting standards (EN 12464-1) recommend 4000K for open plan offices and workstations. It pairs well with cool-toned interior finishes like grey carpets, white walls, and glass partitions.
5000K and Above: Daylight
5000K simulates midday daylight. It is used in inspection areas, medical facilities, colour matching booths, and manufacturing. 6500K represents overcast sky and provides the highest colour accuracy for critical visual tasks.
These temperatures feel clinical in habitable spaces. Avoid them in hospitality and residential applications unless the design specifically calls for a clinical aesthetic.
Tunable White: The Flexible Solution
Tunable white fittings adjust their colour temperature across a range, typically 2700K to 6500K. They enable human-centric lighting schemes that follow circadian rhythms. Warm light in the morning and evening. Cool light during peak working hours.
Tunable white requires DALI DT8 drivers or dedicated wireless control systems. The additional cost per fitting is significant, so specify it where the benefit justifies the investment. Conference rooms, executive offices, healthcare wards, and education spaces are strong candidates.
Consistency Across a Project
MacAdam ellipses define the acceptable colour variation between fittings of the same stated CCT. A 3-step MacAdam ellipse means the colour difference between any two fittings is imperceptible to most observers. A 5-step ellipse shows noticeable variation when fittings are side by side.
Specify 3-step MacAdam or tighter for any visible ceiling plane where multiple fittings sit adjacent. Budget fittings often ship at 5-step or worse, creating a patchwork effect that no amount of design intent can disguise.
EMPRICS Lighting products are available across the full CCT range from 2700K to 6500K, with tunable white options on selected families. All specifications include MacAdam step data.