If you want to figure out a light product is good or not before purchase, the most common criteria you use to evaluate is CRI, or generally Ra. While you may consider those two data as the same. It is better for you to read this article and you will find the difference between CRI and Ra.

The definition of CRI.

CRI is the short name of Color Rendering Index, which is widely regarded as the measurement for evaluating the color rendition ability of a light source.

Theoretically, CRI is a series number calculated according to 15 pre-defined colors, which is so-called Test Color Samples(TCS), for judging each colors rendition’s accuracy of the light source.

Each number relative to each TCS in this series is named as Ri, which rated from 1-100, represents the color rendering score refers to each test color sample. For example, ……………

When got every Ri score, we are able to calculate the general CRI(Ra) and the extended CRI (Re).

General CRI (Ra)

General CRI (Ra) is the average number of R1 to R8. As we can see here, the calculation only adopts 8 numbers, yet R9 to R15 is not involved in the formula.

Extended CRI (Re)

Extend CRI is the average number of R1 to R15. In extend CRI calculation, all Ri numbers are involved in the formula. It is more accurate as we can see more colors rendition performance like some saturated colors, such as deep red and deep blue.

It is the flaw of general CRI criteria. Therefore, it is important to check some special Ri number in extended CRI, such as R9 and R12 which represents two significant colors for film and video lighting and medical lighting.

So, when communicating with different persons, the definition of high CRI varies. Generally, extend CRI is not commonly used in the discussion. For better understanding, it is better to discuss with suppliers or customers in general CRI (Ra) but emphasize the specific Ri number in extended CRI (Re).

In the description or datasheet of MM’s high CRI lights, for avoiding misunderstanding, we will point out the general CRI (Ra) value as well as two particular extended CRI value, R9, and R12 as can be seen in the screenshot below.