Colour Rendering Index

 

CRI stands for: Colour Rendering Index. 

Wikipedia explains CRI by saying: it is a quantitative measure of the ability of a light source to reveal the colours of various objects faithfully in comparison with an ideal or natural light source.
 
Though it does appear to be yet another technical term we must now get our heads around, in very simple terms, CRI allows you to “see” colours more clearly. The analogy I always like to use is that it will allow you to distinguish between black and navy-blue colours more easily.   
 
LED technology is continuously evolving and so is the way colour is measured. For now, CRI is a simple metric to allow us to measure how close a luminaire can reflect colours comparable to the sun and daylight. The benefit of having a light source that is comparable to daylight is your eye’s natural ability to process and distinguish colours.
 
The CRI metric provides an index between 1-100 used to “indicate” how a luminaire will render colours in a space. The higher the number, the crisper colours look to the natural eye.
 
High CRI light fittings have often been left for speciality spaces such as museums and art galleries. This has largely been due to the cost vs benefit of the technology. Evolution in manufacturing styles has now made it more efficient to produce this technology, making it more attainable to achieve higher specification luminaires for a lower and more reasonable investment.
 

What CRI should you look for?

A CRI level within the “80’s” is considered good performance in NZ and makes up the largest percentage of lighting fixture sales locally. 

It offers a good mix of colour clarity and light output. Any product below this would be considered poor and offer washed out “dull” looking colours and conversely anything above the CRI “80” band level is considered great and excellent. To really harness the benefits of high colour clarity, look for luminaries with a CRI of 90 and above.
 

Where should you use a high CRI Luminaire?

It can get a little overwhelming when reviewing LED options. 
With wattage, lumen output, colour temperature and now CRI to assess.
 
A good rule of thumb to apply when considering the use of higher CRI luminaires is to ask yourself if ‘colours’ could be confused? 
Examples of this are: Food prep and intricate workspaces such as reading areas, jeweller’s workshops, wardrobes. Basically, any area where distinguishing colour would be beneficial and make it easier for the user of the room to utilise a space more productively.
 
Considerations – information is king.
Though higher CRI luminaries offer a vast array of benefits, this clarity does come with some considerations. Producing a higher CRI does reduce the luminaries LED chip efficiency. This decreased efficiency reduces the lumen output of the luminaire. The increased colour clarity often trumps the reduction in light output, however, overall consideration needs to be made when designing a space with higher CRI. Often you may need to tweak the number of luminaries in a space to achieve a certain lux level.