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What is R9 and why does it matter for LED lights?

in LED 101

Introduction

Color Rendering Index (CRI) and R9, are two vital elements to consider when choosing LED or necessary interior items. This can be essential for contractors and distributors ideally filling customers needs. Today, color quality is an important consideration when assessing LED lighting for commercial and residential applications.

What is R9 and CRI?

For us to define the term R9, it is first important to understand what the Color Rendering Index is. Color Rendering Index is a rating system that measures the precision of how well a light source generates the color of an illuminated object. It gauges the light sources capacity to display object colors sensibly or normally compared to a conversant reference source, either daylight or incandescent light. Color Rendering Index is an average value based on R1 to R8. R9 is one of the six saturated test colors not utilized in calculating CRI.
Since some percentage of the color Red can be found mixed into the various tints of most processed colors, the ability to precisely reproduce Red is key for accurately rendering colors of displayed objects. Lamps with high R9 values create the most vivid colors.
The Color Rendering Index metric is divided into 14 color ranges from R1 to R14. Color Rendition Index is an average value based on color ranges R1 to R8 of the metric, however, doesnt consider the remaining six extra color references. A high CRI, matched with a high R9 value yields the most precise display of color.

LED R9 Value

What is a good CRI R9 value?

Although the maximum possible value of R9 is also 100, unlike average CRI numbers, R9 should be judged a bit differently.

Mathematically, R9 is far more difficult to achieve a high score compared to the other R values that comprise the CRI calculations, and is far more sensitive to spectral variations. Therefore, an R9 score of 50 or above would be considered “good” while an R9 score of 90 or above would be considered “excellent.”

You will therefore find that most lighting products available in the market will rarely specify the R9 value, and when they do, rarely will they guarantee anything higher than 50. Even at Waveform Lighting, we specify R9 > 80 or R9 > 90, and are unable to guarantee anything higher than R9 > 95 due to this sensitivity.

This is due to the fact that CRI utilizes the CIE 1960 uv color space, which is skewed in a way that exaggerates color differences in the red region of the chromaticity diagram. Since CRI is a calculation that quantifies color differences between a light source and a reference source, a larger calculated color difference will result in a larger decrease in the R score.

good r9 value

Why is red such an important color?

Red is a crucial color for many applications including photography, textiles and reproduction of human skin tones.

Many objects that do not appear red actually are a combination of colors, including red. Skin tones, for example, are very much influenced by the redness of the blood that flows right beneath our skin.

Therefore, a light that lacks red will make a person look pale, or even green. This can be problematic for medical applications where color appearance is critical for accurate diagnoses. In other applications such as photography, aesthetic appearance is crucial and many times cannot be corrected for even in post production and digital editing.

When searching for a high color quality LED, be sure to inquire about the CRI as well as its R9 value.

cri r9 red

Why is CRI R9 important?

CRI R9 is a very important metric because many light sources will be lacking in red content, but this fact will be hidden due to the averaging out of CRI calculations which do not include R9.

As the chart below shows, an light source can actually perform quite well with the first 8 test color samples, scoring quite well for R1-R8. For the general CRI Ra metric, this means that an LED with poor red color rendering can still get by with an 80 CRI (Ra) rating.

CRI R9 value

Why is R9 important in restaurant applications?

People tend to eat with their eyes just as much as they do with their taste buds so the presentation of food, especially in high-end restaurants, is extremely important. Many food items such as meats, fish, fruits, and vegetables carry high amounts of red so if the light bulb that displays those items does not have a proper R9 level,  the food can appear discolored, leading to customer dissatisfaction.

restaurant R9 value

Why is R9 important in retail applications?

If you manage a retail location with clothing on display or customers are trying on clothing articles it’s important to keep in mind that skin tones and some articles of clothing contain strong red tones. The lighting you choose for dressing rooms, display rooms, or accent lighting needs to have a high CRI quality in order to accurately show the true colors of the clothing against the customer’s skin.

retail R9 value

Why is R9 important in art galleries?

One purpose in an art gallery is to accurately display artwork so that guests can view the pieces on display in their truest form, whether they’re looking to view the items for their homes or simply enjoy the art on display. In the accent lighting that highlights that artwork, it’s vital to have quality CRI so all of the colors from the piece appear vivid and attractive.

art gallery R9 value

Why is R9 important in hospitals?

Quality R9 is important in hospitals because it’s the most critical color for surgical procedures. Visibility could actually be life-impacting. Medical professionals need to be able to clearly see all colors displayed properly during both surgeries and general medical procedures, so they can best serve their patients.

The Color Rendering Index and R9 values are two important features when it comes to selecting the right LED lamp for your application.

Now you know why to look for R9 specifications in the light you choose. Everyday life is rife with red, so it makes sense for the R9 value to be a lighting standard.

hospital R9 value

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