What is Color Rendering Index and Why is it Important?

Once it comes to buying bulbs and installing lighting, there tend to be two types of consumers. Some people do not bother to make any thorough considerations and they simply go for the cheapest options or discounted products. On the other hand, there is a segment of customers that could be classified as ‘smart consumers’. These are people, who seriously take into consideration numerous factors when buying light bulbs or any other type of technology. They are most likely to be the ones that are going inquire retailer about such qualities as energy efficiency, life expectancy, color temperature, durability etc. – aspects that are quite crucial if you want to make a long-term investment in terms of quality lighting.

As we know, lighting nowadays is more than just a tool that helps us exclude darkness and gloom during evenings. For instance there are different lighting designs available according to the purpose of your lighting e.g. different lights should be considered to provide light for your workspace and for your bathroom. Color rendering index is probably one of the most crucial of aspects of lighting to be looked at when purchasing any type of bulb. While color rendering is important factor, very few customers actually happen to know what does it mean and why it should be taken into account. This article should help you eliminate lack of clarity related to these matters, emphasizing the importance of color rendering index and explaining its significance in providing quality lighting that would meet both the functional and aesthetic needs.

What is color rendering index?

Color rendering index (CRI) is a measure that shows us how well a light source makes the color of an object appear to our vision (human eye) and how “realistically” (one could also say “naturally”) the light source makes different shades to reveal. In other words, CRI explains how accurately the particular light source is rendering any color in comparison to so called ‘reference’ light source (daylight).

How CRI is measured?

CRI is measured in scale from 0 to 100 where 100 represent the maximum value with the highest color rendering ability. CRI itself is calculated from the differences in the chromaticities (also referred to as “color appearance”) of eight CIE standard color samples that have been illuminated by the light source under test and then again tested by a reference illuminant of the same Correlated Color Temperature (CCT).

Majority of the best bulbs that are considered good at color rendering has a CRI of 85 to 90, but light sources which have a CRI of 90 or higher are known as excellent and are the most appropriate for tasks that require the most accurate color discriminations. Light sources with a high CRI are suggested in various color-critical applications such as photography, neonatal care and cinematography. CRI values that are lower means that some colors, when illuminated by the light source, might appear in unnatural colors. It does not necessarily mean that the bulb is bad or will do harm to your eyesight. It simply means that the colors you will see upon using the particular lighting will differ from the ones you would see during the daylight.

When considering what sort of CRI will fit your situation and particular purpose, keep in mind that CRI is not the same as color temperature which has been described more thoroughly in separate article. For instance 2700K (“warm”) color temperature incandescent light source has a CRI of 100 whereas 5000K (“daylight”) color temperature fluorescent light source has a CRI of 75, but another fluorescent lamp with the same color temperature has a CRI of 90.

Comparison of color rendering with different CRI values. Source -fosilum.si

Comparison of color rendering with different CRI values. Source -fosilum.si

Which bulbs have the highest CRI?

It has to be pointed out that while conventional incandescent bulbs, indeed, ensure the highest CRI and they exclude any color discrimination, they are the least efficient of light sources available. First LED bulbs could not provide high CRIs making many consumers concerned about other advantages of LED, knowing that they are not really made to show colors appropriately. However, a lot of work and scientific effort has been invested in researching possibilities to increase color rendering qualities of LED lamps as well and now there is great variety of LEDs with good and excellent color rendering available in the market.

Using lights to render colors in photoshoot

Using lights to render colors in photoshoot

If you have decided that you will opt for lamps that can provide the highest color rendering, these are the types of bulbs that should be considered:

  • Incandescent bulb (CRI of 100);
  • Tungsten Halogen (CRI of 95);
  • Triphosphore fluorescent (CRI of 85);
  • Metal Halide (CRI of 85);
  • Some varieties of LED (around CRI of 85 and even more).

Why is CRI important?

As said, not every situation requires having a light source that has high CRI. For instance, when illuminating street or pathway, you really do not need to think if the colors of the environment appear in natural colors or not. What you care about in that case is the safety reasons and the main function for lighting source is overall illumination, not its aesthetic qualities regarded to details.

On the other hand, when equipping a photo-set, it is very important for photographers to ensure light circumstances that would emulate natural daylight as much as possible. In that case there is no other way round but to use bulbs with high CRI. Also, when thinking about the interior of your workspace, it is known that “full spectrum” lamps and lamps with high CRIs can promote concentration and higher productivity. Lighting does impact our moods and who would not want to have all the nice colors and details of our home to appear as close to real colors as possible?


Blogger, editor, developer who loves green living. Interested in photovoltaics and solar lighting. Reviewing solar products since 2013.

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