The terms like color rendering index (CRI), correlated color temperature (CCT), light spectrum, Stroke’s Shift are used to analyze the performance of light sources. There have always been comparisons between different light sources on the basis of these terms. Now, with LED lights gaining prominence, the discussion veers towards the comparison between LED lights and other traditional lights on the basis of these terms. This post introduces the terms of the light spectrum, color rendering index (CRI), and color temperature in the context of LED. Further, the terms of CRI and light temperature will be differentiated for application purposes.
The light spectrum is a source of energy that shows red as the less energetic color while violet is the most energetic one. The colors of the rainbow “VIBGYOR” are contained by the light spectrum. A quality source of light should be able to reflect all the colors of the rainbow, or in other words, should reflect all the light frequencies in the range of visible light. VIBGYOR comes under the visible light spectrum but the light spectrum has invisible light frequencies as well. Infrared and ultraviolet are the invisible light frequencies that are not required for human beings. A good quality light source should radiate visible light frequencies and should not radiate any UV or infrared light frequencies.
Considering all the discussed terms of human vision-centric light sources, LEDs are one source that fits in. LEDs effectively radiate the light waves according to the ranging light spectrum of VIBGYOR. They do not radiate UV or IR radiations, therefore they are suitable for human vision. However, the qualities of LEDs differ based on manufacturing standards. Industrially, LEDs are manufactured under certain considerations of terms related to the light spectrum. Now, let’s focus on the color rendering index (CRI) and correlated color temperature (CCT), which help identify the quality of the LED source. These concepts are discussed in detail in the next section.
Color rendering index (CRI) is a measure of the rendering ability of the light source against a black body. In simple language, it is the ability of a light source to radiate or display the varying light frequencies in the light spectrum. Color rendering index (CRI) signifies how effectively the light sources render colors of a rainbow- “VIBGYOR”. CRI is generally rated on a scale of 1 to 100, where the natural light is rated the highest, 100 on the CRI scale. The incandescent bulbs are considered sun, therefore, the CRI of incandescent bulbs is nearly 100. Generally, LEDs have CRI ranging from 75 to 90, which is sufficient to show almost all the light frequencies.
Here is a comparison between different light sources.
| Type of Light Source | Color rendering index (CRI) |
| Sodium Lamps | 25 |
| CFL | 75-85 |
| Mercury Lamps | 50 |
| HID | 72 |
| LED | 75-90 |
According to this data, LEDs can create an almost perfect light spectrum with a high CRI range. Incandescent bulbs can generate CRI of 100 but it is considered harmful due to invisible light radiations.
Correlated color temperature (CCT) is measured in terms of sensation to human eyes, either warm or cold. In technical terms, the correlated color temperature (CCT) is the temperature of an object from which the light is emitted. The range of CCT is modeled via a black body radiator, as the temperature increases, the black body starts radiating visible light of continuous light spectrum.
The color spectrum also influences the atmospheric temperature. The higher the light temperature, the warmer will be the atmosphere. If considered on a larger scale, the color temperature also contributes to global warming. The CCT is measured in Kelvins (K). It might be confusing that the higher kelvin in CCT is cooler than low kelvins in the CCT, but it works opposite to oven temperature. The yellow lights give warmer influence where the blue lights give a cooler impact.
As compared to incandescent bulbs and natural flames, LEDs offer safer CCT. The range of CCT for LEDs is from 2700 K to 9500 K whereas for incandescent bulbs it is 1850 K to 2400 K CCT. This range of LED’s CCT falls under cool to moderately warm white light spectrum therefore is suitable for human eyes. Therefore, the LEDs are preferred over fluorescent bulbs.
Although CRI and CCT have their importance in the light energy resources, CRI gets superior importance while a selection of a light source. The buyers’ light energy sources prefer CRI over 80, therefore, LEDs make significant importance in domestic and commercial lighting. However, CCT holds importance where it comes to appearance due to the warmth and coolness of nature.
As of now, the importance of CRI and CCT for LED is described, now it can help you purchase the right LED light sources. If you are considering LEDs for your commercial or residential uses ensure that you source them from trusted manufacturers or suppliers. E2 Lighting USA is a company that offers various LED lighting solutions for indoor and outdoor uses. Their LED products have less than 1% blue light that makes it suitable for human eyes. They also offer rebates on adopting LED lighting solutions.