Editing Color rendering index (section)

== Special value: R9 ==

R<sub>a</sub> is the average value of R1–R8; other values from R9 to R15 are not used in the calculation of R<sub>a</sub>, including R9 "saturated red", R13 "skin color (light)", and R15 "skin color (medium)", which are all difficult colors to faithfully reproduce. R9 is a vital index in high-CRI lighting, as many applications require red lights, such as film and video lighting, medical lighting, art lighting, etc. However, in the general CRI (R<sub>a</sub>) calculation R9 is not included.

R9 is one of the numbers of R<sub>i</sub> refers to test color samples (TCS), which is one score in extended CRI. It is the number rates the light source's color revealing ability towards TCS&nbsp;09. And it describes the specific ability of light to accurately reproduce the red color of objects. Many lights manufacturers or retailers do not point out the score of R9, while it is a vital value to evaluate the color rendition performance for film and video lighting, as well as any applications that need high CRI value. So, generally, it is regarded as a supplement of color rendering index when evaluating a high-CRI light source.

R9 value, TCS&nbsp;09, or in other words, the red color is the key color for many lighting applications, such as film and video lighting, textile printing, image printing, skin tone, medical lighting, and so on. Besides, many other objects which are not in red color, but actually consists of different colors including red color. For instance, the skin tone is impacted by the blood under the skin, which means that the skin tone also includes red color, although it looks much like close to white or light yellow. So, if the R9 value is not good enough, the skin tone under this light will be more paleness or even greenish in your eyes or cameras.<ref>{{cite web |url=https://www.mmsvideolight.com/why-r9-is-important-for-high-cri-lighting/ |title=Why R9 is important for High CRI Lighting? }}{{Dead link|date=March 2022 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>