CRI or Colour Rendering Index in simple terms is a way to grade the quality of the light emitted from an LED light source or luminaire.
In general the sun provides crisp, clean white light, it presents colours in their natural state so the human eye can easily register what it's looking at, it is probably the worlds highest CRI but since its hard to measure and its always changing throughout the day with angle and weather conditions its not a reliable cross check. That's why scientists use a black body locus as the reference.
Unless you are scientifically minded lets just say this is what the scientific community decided would be the standard to make it easier for all manufacturers to test their products against. It might not be the best method since LEDs don't really work like an incandescent lamp but it still is the standard until such time as someone finds a better way. For now, there are many discussions in the works but nothing has changed and it may be some time before it does.
Artificial light sources need to be graded for their quality of the emitted light to ensure colours, shading, depth perception is all accounted for. This is where the Colour Rendering Index CRI comes in. (Don't confuse CRI with CCT or Correlated Colour Temperature they are not the same but they do work hand in hand.)
In the LED world it is possible to replicate high CRI light sources like a Halogen globe by mixing the Red, Green and Blue spectrums in a very precise way during manufacturing, the only problem is a Halogen really only comes in one colour temperature (CCT) 3000k or Warm White. LED on the other hand can be mixed and matched to provide many different colour options from 3000k Warm to 6500k Cool white which is a much wider spectrum than we have ever had available before. To achieve high CRI of 80-95 the colour temperature is usually limited from 2700k - 5000k, any higher colour temperature and the light quality for meeting high CRI starts to look a little weird, it might meet the testing machine idea of high CRI but the human eye just doesn't agree in some cases, this can also change from manufacturer to manufacturer.
Like everything in this world there is always a compromise, nothing is for free, to achieve high CRI levels for an LED the luminous flux or lux output is reduced usually by 5-15% depending on the LED, manufacturer and process being used. In the early days of LED CRI of 60-75 was considered a good achievement, but in recent times CRI of 95-98 is entirely possible and in some retail locations CRI92 is the minimum specification.
In general the following CRI values would suit specific environments.
CRI >70 - Warehouse, low accuracy manufacturing, machine shop or anywhere where colour recognition or representation is not required. Its probably not a good idea to have CRI70 lights over a printing press where checking colours is important.
CRI >80 - residential, commercial, retail, high detail manufacturing
CRI >90 - residential, commercial, retail, printing, art studio.
From our experience some lighting suppliers are not telling the whole truth since its hard for the human eye to tell the difference if you don't have a reference to look at first. How do you know if the reference is accurate? It all gets very confusing very quickly and hell, its lighting who really cares anyway. It's also very easy to doctor up test reports at the factory level and pass them off as accurate. Essentially it is a case of buyer beware.
So while there is a push to get the maximum performance out of LED lighting there are so many variables that it's a minefield even for those in the industry. At lot of the big manufacturers or suppliers are working within the industry trying to shape the future to their own benefit, which is fine provided that is actually of benefit to the customer and not just their bottom line, which in some cases it is found to be but in general the big manufacturers are doing their part to help standardise the LED lighting industry. Up until the last 18 months it has been a little bit like the old west and will continue to be for a little while yet.
When selecting an LED light fitting for your next project its a good idea to check the luminaires next to each other for reference. You will see within the first couple of seconds if you like the look of the emitted light or not. Does it show colours in their natural state, is it easy on the eye or does it just look plain wrong. Once you have selected the luminaire and the right colour temperature check to see if you are happy with the High CRI version or is the lower CRI version acceptable. Sometimes its hard to tell the difference between 80 and 90 CRI light sources and in some cases the 80CRI looks more natural.
The final thing to consider is the price. Remember the part about the compromise, this is another area unfortunately. CRI90 is more expensive and time consuming to produce in an LED. The manufacturers are starting to refine the process and over time it will become easier, but like anything to get a high quality result it will cost a little more time and money.
SeerLED works very closely with our factory to ensure we use completely genuine LED light sources, from Citizen to Philips, Luxeon, Nichia and Edison to name a few. We are constantly checking quality control during the manufacturing process to ensure what we offer is the best we can get. We also manufacture many samples of the same light with different CRI and CCT values to see which one looks best for the most important test of all, The Human Eye.
While this all might seem like mumbo jumbo lighting jargon, its very important to have a basic knowledge. Next time your at your local shopping centre have a look at the different LED lighting products being used, some are so good you didn't know they are LED and others are so obvious it gives LED a bad name. Just remember, like anything in this world you get what you pay for, ask for a $10 solution and expect $10 results, in the short term your pocket feels good but in the long-term you will wish you didn't.
Please note that certain images used to showcase designs and explanations have been obtained from third-party sources.
SeerLED does not assert ownership of these images and has utilised them solely as an illustration please contact us if want these removed or credited.