Colour temperature is not colour rendering

Colour temperature in kelvin describes the appearance of white light: lower values look warmer, higher values cooler. It does not tell you how accurately materials or merchandise appear. The colour rendering index Ra describes a different property.

Sources with the same colour temperature can render colours differently. Code 840, for example, means Ra 80–89 and 4,000 K. Colour-critical work and retail displays benefit from carefully selected rendering and colour consistency, with samples where appropriate.

Colour consistency also matters when work is completed in phases. Different variants or batches can look different alongside one another. Specify and record colour requirements early. For colour-critical uses, view samples with the actual merchandise or materials rather than comparing only a white wall under different luminaires.

What to clarify for your project

• Select colour temperature for the application.
• Specify colour rendering for material and colour inspection.
• Coordinate colour appearance across adjacent luminaires.

Remember: Consider kelvin, Ra and the application together.