When you are trying to select the right lighting for your application, the colour rendering index (CRI) goes hand in hand with colour temperature.
I'm going to unpack the obstacles around CRI in this article and include some practical tips for making the right choice. Click here to read a guide to colour temperature selection for your lighting if you need to catch up on the colour temperature.
Some of the information behind CRI and where the industry is going are part of the first half of this report.
What is color rendering index?
To predict how good a lighting product's visual performance would be, CRI is an easy and helpful lighting spec.
Simply put, the metric is a number between 0 and 100 used to predict how well colour is made by a product. Beneath the brightness, the closer to 100, the better or truer colours can appear.
Main word in this: Can.
CRI is determined based on how well eight particular pastel colours are made by a light source. The idea is that if a light makes certain colours well all colours should be well made.
Here's an example showing the difference between low colour rendering light (left) and high colour rendering light (right) provided by the National Institute of Standards and Technology (NIST). What one would you like to have?
On additional swatches, certain manufacturers test the efficiency of their products (if you have ever heard a reference to R9, that's a measure of how well a product can make red colours).
Another colour performance index named the Color Quality Scale, or CQS, was also created by the National Institute of Standards and Technology. To assess light brightness, it uses 15 colours.
In CRI, R9, and CQS research, here are the various swatches used:
Technology in colour rendering
As lighting technology has improved, so has the right CRI picked.
Picking the CRI was straightforward with fluorescent and high-intensity discharge (HID) illumination. There were consistent price points and variations in the product if you switched from a normal to a high CRI.
You start to get a bit confused with LED by choosing the right colour and CRI combination.
In reality, an industry-wide quest for a metric other than CRI has prompted the advent and proliferation of LED lighting today, which better measures the visual output of modern lighting technologies. The truth is that in today's lighting industry, a high-CRI product might not be a magic bullet for you.
In that search, especially with the introduction of TM-30-15, great strides are being made. TM-30-15 is a more coherent way to pick the right lighting product, the Office of Energy Efficiency and Renewable Energy says. To look at the difference between effectiveness and colour rendering, it integrates many different measures and can help select the best light for particular applications.
A new technology called colour pumping that improves and saturates the colour spectrum has also emerged. With vibrant and vivid goods, it operates ideally in retail. Philips calls theirs "crisp white," Xicato calls theirs "vivid," and Solais calls theirs "aggressive."
This is where CRI can actually be deceptive, because instead of matching a reference source, the purpose of this is to actually oversaturate and accentuate those colours (mainly blues, blacks, whites, and greens).
A guide to selecting an index for colour rendering
You have spent money carefully designing the surfaces, environment, products, and other precise information of your room at this stage. Or maybe you're on the other end of the spectrum and in your room you only need brightness, but the quality of colour is not as important (like in parking garages). How do you decide what's right for you with CRI?
As a rule, a CRI of 90 or more is considered to be high and mid-range to low is considered something below 80. If colour quality is significant, seriously consider something in the 90s.
Otherwise, you may want to weigh other variables like light intensity or wattage first and CRI as a secondary option.
It is also worth noting that light quality changes include adding more phosphors. As a consequence, as you switch to LEDs with better light characteristics, you usually make a compromise in energy efficiency. This sacrifice is worth it in the majority of cases.
Here's an easy guide that will help point you in the correct direction:
There is really no alternative, as with colour temperature, for getting a few samples and putting them in your room to see how things look. You could be surprised by the success of an 85 CRI product and disappointed with a 95 CRI product.
On the other hand, you can see the difference that it makes and decide to upgrade from low-CRI HID lighting to mid-range CRI LED lighting. If you are looking for retail or gallery lighting that stands out, you might also be ready to accept a product that takes advantage of the colour pumping technology previously described.
No matter the case, we are here to help you navigate to the right product for your needs.