Lesson Two: Colour temperature and CRI

Colour Temperature Kelvin

Colour temperature is an indicator of eye comfort

So what is colour temperature? Light colour temperature is represented in the unit of absolute temperature, Kelvin. To put these numbers into perspective, around our homes we typically choose lights with colour temperatures of 2700K (warm incandescent), 3000K (warm white halogen) and 3500K (household fluorescent). Colour temperatures higher than 3500K are typically used for commercial and hospital applications, and 4000k for task/ commercial applications.

When applying what we know to the driving environment, contrast is key. Night drivers want clarity not glare – trees, roads and obstacles need contrast to be seen. If the colour temperature is too high, objects in the distance will appear white and glaring, causing eye fatigue and squinting… but if you need a powerful light, the eye discomfort can be mitigated with a good CRI score, without losing out on brightness…

CRI is one of the many differences between cheap and quality LED lights

‘CRI’ stands for “Colouring Rendering Index”, and it’s pretty important when it comes to lighting. CRI measures how easily the human eye can distinguish between different colours – and when you have a powerful light, you need to have a good CRI score to reduce glare and comfortably perceive any hazards on the road. Lightforce lights are all built with a minimum of 80 CRI.

To put this into context, natural daylight has a score of 100 CRI, and cheap LED lights usually sit around 60 CRI – very uncomfortable and tiring for the eyes. Next week we’ll be talking about one of the most hotly-debated driving light topics – lumens, lux, and the relevance of distance! See last week's lesson here: Watts