Saturday, 11 May 2013

What does CRI mean in lighting?

It means Colour Rendering Index, and is usually given as a number.

Sunlight is usually equated with a perfect colour-rendering (scoring 100). This means in broad terms that a colour-chart would look the way it was intended when viewed in fairly neutral sunlight.
But if you brought that colour-chart under most old industrial lights many of the colours would look much less intense or even shift.
Old-technology fluorescent tubes gave colour rendering as low as CRI=50 but yellow sodium industrial lighting was even worse!

Modern lighting aims at CRI of over 80, which most people feel is acceptable to give fairly realistic interior colours.
However art studios and printing companies may want CRI of over 90 for extreme accuracy.

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These are just my tips based on experience as a lighting enthusiast surveying sites and speccing energy-saving lighting in hundreds of buildings over ten years, and I know other people will have had different experiences (maybe different products and technologies too) so please feel free to share your own experiences here.