How important is Color Rendering Index (CRI) in my purchase decision?

CRI is a specification that we simply think of us quality of light. Quantity of light is a measurement of lumens, and quality of light is a measurement of CRI. CRI is a scale between 1 and 100. 100 being great, 1 being terrible. What you need to know is that 6 reference colors are tested to determine how good a light performs against the CRI specification. And it is in this test against these 6 spectrum's that a lights CRI value is determined.

So how much do you need? It really depends who you are. Are you a retail store like the Gap or Bed Bath and Beyond? Are you a car dealership? Are you a hospital that wants to replace your parking lights? Are you a factory, a warehouse or a school? Different businesses and facilities all have different needs.

If you are a retail shop selling to consumers, high CRI is good. 80+ is preferred. 85 is great, even 90. If you are a not a retailer, then 70+ will be just fine. But can you visibly see the difference between 70 CRI and 90 CRI. Then answer is yes, if you know what to look for. At a recently lighting trade fair, we walked into a booth that displayed a series of glass bowls of colorful gumballs. Each bowl was under a LED light, and the CRI of that light was labeled above the bowl. We walked from the 70 CRI display all the way to the 95 CRI bowl and thought to ourselves "We're not seeing the difference". So then an engineer walked up to me as we kept on walking from bowl to bowl and he told me to "Look at the red gumballs". And sure enough, the red gumballs became brighter and more vibrant as the CRI increased. The other colors seemed similar from one display to the next.

So, as a factory or a warehouse manager, do you care if the reds in your warehouse are not as vibrant under 70 CRI than under a 95 CRI light? Are you prepared to pay more for that difference? Probably not. If you own a clothing store, then you probably want the best quality of light available.

Comparing LED to Metal Halide and High Pressure Sodium

This is many ways is not even a fair fight. Especially when you compare High Pressure Sodium to almost every light source available on the market today. High Pressure Sodium CRI is somewhere between 20 and 40. The color temperature is somewhere around 2300K, so what you have is a very warm (yellow) light that tends to discolor everything. Did you notice how everything under a HPS light looks yellow? That in fact, is the perfect example of poor CRI. Good CRI makes colors look as they should appear, bad CRI discolors everything. Metal Halide fairs better. Its CRI is much better than HPS, but typically lower than LED. So the light quality of Metal Halide is not as good as LED.

In fact something else happens with Metal Halide bulbs. A brand new Metal Halide bulb is very bright right out of the package, but every one knows it loses it lumens very quickly. Within the first 6 months of use (assuming 12 hours a day), the lumens can drop as much as 20%. By the time the light is 50% though its 15,000 hour life, it can lose as much as 50% of its initial lumens. But what is less known is it appears that Metal Halide loses its CRI effectiveness as lumens depreciate.

So not only is the quantity of light dropping, so is the quality of light. Its a double hit on the amount and usefulness of light. It appears Metal Halide bulbs are like fireworks. Bright to start, but fizzle out quickly. So in the world of HID lighting, not only does it make sense to replace these lights with LED because of the dramatic and significant savings available when you convert over, but the quality of light will also improve.

In summary, the most important thing to remember about CRI is that you should think about the application that the lights are going to be used for. The majority of installations do not need to purchase higher cost high CRI lights. But when the need arises, they are available for those applications that need to make product or colors stand out.

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