Before switching to green, energy-efficient lighting started to gain traction, selecting a light bulbs was fairly simple. If you were not getting enough light from your 40-watt or 60-watt bulb, the solution was simple, just go up to a higher-wattage bulb. Voila more light. It was really that simple!
Now, with the rapid growth of LED technology, a new world of possibilities have developed in terms of performance and features. Even though this is wonderful news in terms of advancement of environmental technologies and for commercial or industrial applications, the downside is that for the average consumer it adds another layer of confusion on purchasing new light bulbs, thus making the whole process over complicated.
With all of the various color and light terms floating around, it can be exhausting and frustrating to determine what kind of light bulb to purchase. We're here to shed some light on the subject and help explain the difference between two of the most challenging terms that are often confused with one another when it comes to bulbs, CCT (correlated color temperature) and CRI (color rendering index).
What is CCT, or Correlated Color Temperature?
CCT is a number, measured in degrees Kelvin, which helps to describe how warm or how cool a light source is. The majority of light bulbs range from 2700K (warm, mimics the look of incandescent color) to 5000K and higher (bright, white daylight color like what's portrayed outdoors on a sunny day).
When it comes to residential applications, 2700K and 3000K are popular color temperature options, since they both create a warm and inviting atmosphere, thus creating a more relaxing environment.
However, when it comes to retail and commercial applications, the preferred choice is the other way around. 4000K is very popular since it provides a cleaner, more crips shade of white. In task-oriented or industrial applications, 5000K or 6500K is preferred, since these color temperatures match natural daylight more closely.
What is CRI, or Color Rendering Index?
The term CRI describes how accurately a light source illuminates colors of an object. Its value is graded on a scale of 0 to 100, 100 being the best. The majority of standard bulbs have a CRI value of 80. For bulbs to be classified as High CRI, the CRI value has to be 90 or higher.
Here's an example, if a portrait is displayed under a light source with let's say a 70 CRI, the colors would not be correct, nor accurate. However, if you take that same portrait and place it under a light source with a CRI of 90 or higher, the colors would be more vivid, and look accurate and natural.
Difference between CRI and CCT explained
As we have explained, CCT and CRI measure two different aspects of color. CCT lets us know the color of light that is being emitted by the light bulb, which is highly noticeable, even to the average consumer if they're looking directly at the light source.
On the other hand, the CRI value does not let us know what color of light is being emitted. It tells us the color appearance of objects under the light source, or how the colors of an object are being rendered. No one can determine a light bulb's CRI value just by looking at the light its emitting, it can only be estimated by looking at the colors of the object being illuminated by the light bulb. The only way to accurately measure a light source's CRI is with the use of specialized spectral measurement devices. Lighting manufacturers utilize these devices to publish a light bulbs specifications and to guarantee their color rendering values.