​The Color Rendering Index (CRI) measures a light source's ability to render colors accurately. A high CRI means that colors will appear more vibrant and true-to-life under that light source, while a low CRI means that colors may appear dull, muted, or distorted.

Color Rendering Index (CRI) Scale

The CRI scale goes from 0 to 100, with higher numbers representing better color rendering ability. Most light sources have a CRI of 80 or above; anything below that is generally considered poor. However, there are some applications where a lower CRI may be acceptable (or even preferable). For example, some artists prefer incandescent bulbs for their warm, yellowish light, even though they have a CRI of around 60.

Using (CRI) To Measure and Compare the Reflected Color

The colors of the visible spectrum are reflected because they are part of the light emitted by objects.

Red, orange, yellow, green, blue, and violet light are all reflected by different objects because they have different wavelengths. The colors we see are determined by the wavelength of light being reflected. For example, red light has a longer wavelength than blue light, so red objects will reflect more red light than blue light.

The CRI measures how accurately colors are reproduced under artificial lighting.

In other words, it helps us to identify how accurately colors are reflected under artificial lighting compared to natural daylight.

Some artificial light sources may not equally reflect all the colors in the visible spectrum. For example, a light source with a low CRI may make red objects look more orange than red. This is because the low CRI light source is not reflecting enough red light for us to see the object's true color.

A high CRI rating means that the object will look consistent regardless of the type of light used. This is important for ensuring that products look the same in all types of lighting, both indoors and outdoors. Good color rendering can make a big difference in how an object looks, and a high CRI is especially important for products sold based on their colors, such as makeup or clothing.

High CRI lighting is also becoming increasingly important in general lighting applications, as it can make a space appear more vibrant and inviting. LED lights are often able to achieve high CRI ratings, making them a good option for both indoor and outdoor lighting.

How is CRI measured?

There are several different ways to measure CRI, but the most common way is to use a set of eight standard colors. These colors are: red, yellow, green, blue, cyan, magenta, white and black. The CRI score is then calculated by comparing the colors of a test light source to these eight standard colors.

Why Is CRI important?

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CRI is important because it helps measure a light source's ability to accurately render colors. A high CRI means that colors will appear more vibrant and true-to-life under that light source, while a low CRI means that colors may appear dull, muted, or distorted.

CRI/Ra Comparison of Different Light Sources

Sunlight has the highest CRI/Ra of any light source, so it is the standard by which all other light sources are measured.

Incandescent light bulbs have a high CRI/Ra, but they are less efficient than other types of light bulbs.

Halogen lights are very close to sunlight in terms of CRI/Ra, so they are excellent for tasks that require color accuracy, such as art or photography.

LEDs typically have a very high CRI/Ra, making them excellent for tasks that require color accuracy.

Fluorescent lights also have a wide range of CRI/Ra values, depending on the type of fluorescent used. Some are quite good for color rendering, while others are not so good.

Sodium-vapor lights have a lower CRI/Ra than halogen lights, but they are still decent for most tasks.

How do I choose CRI?

Now that you know what the Color Rendering Index is and how it works, you may be wondering how to choose the right CRI for your lighting. Here are a few things to keep in mind:

- The type of light source: Different types of light sources have different CRIs. For example, sunlight has a CRI of 100, while fluorescent lights have a CRI of 60-85.

- The application: The type of application you are using the light for will also dictate the CRI you need. For example, if you are using the light for general lighting, you will want a high CRI to make the space appear more vibrant. However, if you are using the light for a specific purpose, such as makeup application, you may want a lower CRI to create a more natural look.

- The environment: The environment you are using the light in can also affect the CRI you need. For example, if you are using light in a studio with white walls, you will want a higher CRI to make the colors pop. However, if you are using the light in a dimly lit room, you may want a lower CRI to create a more relaxed atmosphere.

You should also consider color temperature while choosing the best light source.

For instance, while incandescent lights have a high CRI, they are not perfect for color rendering. This is because they produce a "warm" light, which can make some colors appear distorted. For example, reds may appear orangey, and blues may appear purplish. If you are looking for accurate color rendering, you may want to consider other types of light sources, such as LED lights.

Bottom Line

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To sum it up, the Color Rendering Index is a measure of how accurately colors are rendered under artificial lighting. A high CRI means that colors will appear more vibrant and true-to-life, while a low CRI means that colors may appear dull, muted, or distorted. The type of light source, the application, and the environment will all dictate the CRI you need. ​