Colour Temperature: Why it Matters and How to Get it Right
Modern lighting infrastructure should create safe, attractive spaces for people, respect wildlife, protect habitats and minimise disruption to circadian rhythms.
Lighting systems must allow people to see properly and distinguish colours. The Colour Rendering Index (CRI) measures how well a given light source shows the real colour of objects compared to daylight. A high CRI is crucial in places where accurate colour is important like production lines and art galleries.
The Correlated Colour Temperature (CCT) refers to the warmth or coolness of a light source. It plays a huge role in both protecting nature and giving users effective lighting after dark.
Understanding Correlated Colour Temperature
The electromagnetic spectrum spans radiation from radio waves to ultraviolet. Visible light sits roughly in the middle. CCT is a useful concept for understanding the different shades of white, which range from warm to cool.
Colour temperature is measured using the Kelvin (K) scale. The warmer the colour, the lower the colour temperature. Candlelight is around 2,000K while daylight is typically 5,500 – 6,500K.
The colour temperature for LED luminaires varies between amber, warm white, neutral white, and cool white.
- Cool white LEDs (5,000 – 6,500K) are ideal for sports and industrial settings. The light is crisp, helping athletes to track fast objects and workers to see details for quality control.
- Neutral white LEDs (4,000K) are usually used for lighting roads and motorways as well as architectural and façade lighting to reveal true colours and let details shine.
- Warm white LEDs (1,800 – 3,000K) are recommended for residential areas, heritage sites and city centres to making them welcoming at night. They are also ideal for parks to avoid disturbing wildlife.
- Amber LEDs are reminiscent of the old low-pressure sodium lamps and are recommended for stargazing, observatories and ecological zones.
- Red LED lighting is an emerging technology. While it has been shown to benefit bat populations, research into its impact on insects is ongoing.
Why Does Colour Temperature Matter?
Different colour temperatures are suited to different spaces. Warm whites are comforting and do not disrupt night skies. Cool whites provide ultra-sharp visibility but research has shown that blue-rich white light (very cool temperatures) can disrupt the circadian rhythms of people and animals.
Sensitive lighting helps preserve biodiversity in nocturnal corridors and less light pollution is always popular with residents and visitors. However, cool LEDs are more energy-efficient, offering lower running costs and a smaller carbon footprint.
When lighting a space, it is important to strike the right balance between affordable, energy-efficient lighting that is also warm enough to respect nature. Amber and warm white lighting are less efficient, but neutral and cool light contains more potentially disruptive blue wavelengths. Finally, amber light has a lower CRI, meaning that people can struggle to distinguish colours.
While there are many factors to consider, we offer two solutions that can provide lighting that benefits people, plants and animals: FlexiWhite and Coloured Lenses.
What is FlexiWhite?
FlexiWhite ensures that the right colour temperature is always available. Whether it relies on pre-programmed scenarios, a smart lighting platform such as Schréder EXEDRA, sensors or a combination, it gives you the flexibility to provide the right colour temperature, whenever and wherever you need it.
FlexiWhite is available in four versions which enable precise colour temperatures to be adjusted from 1,700K up to 4,000K. The colour temperature changes smoothly across all dimming levels, and the light distribution remains precise and consistent.
Specific range options, such as the 2,200K to 3,000K version, offer added benefits in terms of asset lifetime as less power is used when switching between lighting levels with a lower range difference.
What are Coloured Lenses?
Countries such as Chile are passing progressive legislation on light pollution, including strict limits on blue light emissions from outdoor lighting. While working with our customers to help them comply with these regulations, our engineers developed a simple solution: coloured lenses. By fitting yellow or amber lenses to our standard luminaires, the LED remains extremely efficient, but blue light is filtered out, resulting in a warmer colour temperature.
Another advantage of this system is that it offers a higher CRI than true amber light (1,700K). Amber light does not render colours very well; think of the sodium lighting, where everything looked yellow after dark. Coloured lenses keep blue light levels below 1% or 7% depending on whether amber or yellow lenses are fitted, but the rest of the colour spectrum remains. This means they offer a higher CRI coupled with warm white light and great energy performance.
Why FlexiWhite?
FlexiWhite is perfect for cities and urban planners looking to preserve biodiversity while maintaining flexibility. The colour temperature can be set at 1,700K by default to ensure safety and when motion is detected the colour temperature rises to 3,000K to ensure safety. Alternatively, a pre-programmed scenario can reduce the lighting levels and colour temperature after people have gone home, allowing wildlife to enjoy peaceful nights.
Research by the engineering consultancy ARUP shows that the human visual spectrum reacts better to warm light. Their research also found that young women perceived urban spaces with warmer colour temperatures as safer.
Why Coloured Lenses?
Coloured lenses are a simple, affordable solution for those who want the energy efficiency of a cooler LED, without the harsh blue light wavelengths. The lens is permanently attached to the luminaire, so the colour temperature cannot be changed when traffic approaches or as evening falls. While the colour temperature is fixed, brightness can be adjusted via a smart lighting platform to deliver additional energy savings.
They can be a good solution for situations where lighting owners want to reduce blue light but have a high CRI with good energy performance.
Flexibility Above All
An important caveat: colour temperature is not the only factor in adjusting lighting. Installing a control management system (CMS) such as Schréder EXEDRA which can optimise light levels, motion sensors which activate lights when people or vehicles approach, pole height, positioning of the light source… the list is endless.
Schréder is a proud member of the DarkSky certification programme, and all our solutions comply with strict international and local requirements. Certification requires restricted levels of blue light with a correlated colour temperature (CCT) of 3,000K or less, along with minimal upward-directed light flux and glare.
Whatever approach you want to take, we can customise it to suit your needs. Both FlexiWhite and Coloured Lenses can be combined with our other services to create a solution that meets safety, sustainability and environmental impact requirements while staying within budget.
Consult our experts