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Color rendering: A crucial consideration for health care lighting

In hospitals and other health care facilities, the color rendering of light sources in the space can either serve as a critical diagnostic tool or a significant barrier to appropriate treatment. That’s why, if you are responsible for selecting light sources for your hospital, clinic or other patient care facility, it is important to pay attention to factors beyond basic energy efficiency, lamp life performance and upfront cost.

Following are important color rendering considerations for lighting in health care and light sources that provide superior solutions for achieving these goals.

Evaluating light sources for their color rendering ability

In a health care setting, selected light sources must be able to render the true color of objects, materials and skin tones. This is because physicians and nurses consider the color of patients’ skin, eyes and organs in order to diagnose medical conditions, recommend appropriate treatments and track recovery.

The ability of a light source to illuminate the color of objects in a real or natural way, a quality also known as color fidelity, is measured by the color rendering index (CRI).

The CRI value of a given light source describes how closely that light matches the color characteristics of daylight or incandescent light, with 100 being the maximum CRI value. Higher CRI values mean the light source offers better, truer color rendering, while lower CRI values mean some colors may appear unnatural or less vibrant when illuminated by a particular light source.

As the CRI rating of a light source decreases from 100, colors become less distinct, grayer and more muted.

  • Lighting with a CRI rating of 90 to 100 is considered excellent. The color of objects illuminated by these light sources will maintain much of the vibrancy and color integrity experienced in daylight.
  • Lighting with a CRI rating of 80 to 90 is less effective yet still renders colors well, with limited distortions.
  • Lighting with a CRI rating of 70 to 80 or lower, however, has significant deficits. The crispness of the image begins to fade, and the depth of colors rendered is noticeably different.
  • Lighting with a CRI rating of less than 70 may reveal grayer colors and complexions, making people and the surrounding environment appear even duller and more faded.

In the field of medicine, where accurate color rendering functions as a critical diagnostic tool, lighting must achieve high CRI scores. In the past, 80 CRI was generally considered the minimum requirement for lighting in a health care setting. However, today lighting specifiers generally request lighting with a CRI rating of 90 or higher.

Health care lighting solutions for appropriate color rendering and color uniformity

Incandescent, fluorescent, halogen and LED light sources all offer 90-plus CRI values at various price points and efficiencies. However, LEDs have stimulated additional measures for evaluating color rendering, because they offer greater control over the spectral wavelength.

In 2015, the Illuminating Engineering Society (IES) developed a new system to evaluate and communicate the color rendering properties of a light source. The system, IES TM-30-15, considers color fidelity and gamut at a granular level. It offers a comprehensive way of evaluating and thinking about color and light.

This new set of metrics covers not only the color fidelity of a light source (Rf), or the accurate rendition of colors, but also addresses the level of saturation provided by the light source with the color gamut metric (Rg).

Rf is comparable to the traditional CRI rating, with some improvements, including:

  • A finite 0 to 100 scale
  • An increased number of color samples used to generate performance data

Rg, which did not exist in the previous color rating system, quantifies whether a light source displays an average increase or decrease in saturation when compared with a reference source.

Lighting specifiers, manufacturers and others can use IES TM-30-15 to identify appropriate light sources and evaluate color rendering and efficacy. This results in richer tones and better light quality, both of which are critical for health care spaces such as physician examination rooms, surgical suites and radiology reading areas. For example, sources that render skin with high fidelity should be selected for patient exam rooms. In this case, the Rf score should be above 90, and the Rg score should be near 100.

Today, high-performing LED luminaires provide a far superior alternative to conventional light sources in every category that is important for the health care environment. While many fluorescent sources achieve 90-plus CRI values, LEDs are far more controllable while also providing superior color rendering and lifespan.

In addition to providing the right lighting for hospitals and other patient care facilities, modern LED fixtures reduce the cost of lighting energy and lighting system maintenance. This, in turn, frees up significant and valuable resources that can be rerouted to support the business of care.