Choosing LED Lighting Color Temperature (Kelvin) and Color Rendering Index (CRI)

Choosing LED Lighting Color Temperature (Kelvin) and Color Rendering Index (CRI)

Polar Ray Admin

The LED lighting revolution is providing wonderful artificial lighting options which were never available in the past. In concert with the energy savings, which is the initial bottom line that most folks understand when it comes to the use of LED technology, one of the most revolutionary changes in lighting choices is the color temperature (Kelvin ratings) that are available. Initially, the selection of lighting possibilities was limited to incandescent lamps of one sort or another. Until the advent of fluorescent lighting and, eventually, compact fluorescent (CFL) bulbs, there was little to no thought in regard to the color temperature of the light that was produced, especially in lighting that was accomplished by bulbs with an Edison base (the standard threaded base found on conventional incandescent light bulbs). Those old incandescent bulbs were only available in a general warm white color temperature which would be rated in the neighborhood of 2400-2600 Kelvin, which is about as low on the Kelvin scale as the ratings for artificial lighting purposes go. The fact that we now have choices as to the color temperature of our lighting needs is a real game changer in the lighting of different areas in our homes and workplace environments.

The color temperature ratings are divided into three basic Kelvin scales. Those are; warm white, bright white and cool white/daylight.  The warm white color is generally considered to be in the range of 2600-3200K and is more of a yellow color when compared to the next two. The bright white range is 3200-4000K, which is not as yellow due to more red and blue in the output spectrum. The cool white/daylight designation belongs to lights which are in the 4500-6500K range and create more of a bluish tint. As the daylight designation suggests, these lights can come close to approximating daylight (as observed outdoors in the daytime with an overcast sky and the sun at about 12 noon).

The different color temperatures allow for a complete visual, and working comfort change in areas which, previously, may have been illuminated with incandescent light or common fluorescents. The changes in the overall ambiance of a space can be like night and day when different color temperatures are introduced. No longer are the lighting possibilities limited to the somewhat drab incandescent light, or even the more color selectable fluorescent light. Although the fluorescent lighting route can provide different color temperatures that standard incandescent bulbs cannot, the actual quality of the light produced by common fluorescents is really no competition for modern LED lighting. The different color temperatures can even be mixed with outstanding results; for example, a space might be illuminated with area lighting that is lower on the Kelvin scale, but task lighting within the space might best be accomplished with a higher color temperature rating.

In conjunction with the different color temperatures, the Color Rendering Index (CRI) rating that is associated with LED lights is an important and mostly unheard of characteristic of lighting prior to the LED technology. The CRI index is a measure of a light source capability to reveal the true color of an object in comparison to the color presented by natural light. This is not to be confused with the color temperature, which is related to the actual, perceivable color of the light itself. The CRI is defined by the International Commission on Illumination (CIE) as, “the effect of an illuminant on the color of objects by the conscious or subconscious comparison with their color appearance under a reference illuminant”. That “reference illuminant” is generally considered to be natural daylight. The highest possible CRI rating is 100, and such a rating would be associated with a light source which would be identical to standard natural daylight. Some light sources, such as low-pressure sodium, are considered to have negative CRI. This is generally called out as zero CRI, even though the actual measurement may be negative. Such lighting is considered to have no color rendering ability whatsoever. LED lighting is, typically, in the 80+ CRI range but some manufacturers have attained much higher ratings which can reach as high as a 98 rating in some cases. Standard incandescent light is rated somewhere in the 50 CRI range, as is basic fluorescent light. However, unlike incandescent, fluorescent lighting is available in higher CRI standards, such as the expensive tri-phosphor type which can reach into the 90 CRI range. Still, the overall high quality, various selection options, and energy and environmentally friendly features that are available with LED lighting are untouchable by any other form of artificial lighting.

There are other ratings in the lighting field that go above and beyond what the normal person would be interested in, and in all reality would be necessary to be interested in, in regard to the selection of lighting possibilities for applications around the home.  However, the Kelvin and the CRI ratings are an important consideration that was not given much thought prior to the LED lighting revolution.

As always, if you are in need of some assistance in regard to your potential selections for your lighting projects, please feel free to call Polar Ray, at 303-494-5773, and speak with a lighting consultant.