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    Revisiting quality of light in the era of Ledification

    Lighting professionals many times refer to quality of light when describing the lighting effect of a specific luminaire or lighting design without considering the bigger picture. Broadly speaking, quality of light refers to the visual aspects of light and its dependencies on and interaction with people and the environment. 

    Because quality of light is such a broad term, and because it includes so many different aspects, precisely defining it is difficult. It’s like asking what “quality of food” might mean. Quality of food could refer to the quality of the ingredients used in a dish, and to the expertise with which they’re combined—the proportions, the seasoning, the cooking method and time, and so on. It could also refer to your experience of serving that dish in a restaurant—an experience that includes presentation, taste, price, and how it makes you feel.


    Quality of light is similar. It refers on the one hand to the ingredients of light—the different measurable aspects of luminaires and the light they produce. And it refers on the other hand to the perception of light—how light influences the look of spaces and objects in different applications, and how it affects the people who use and manage those spaces. 

    Several well-known measures quantify the physical characteristics of light, such as Color Rendering Index (CRI), Unified Glare Rating (UGR), and Correlated Color Temperature (CCT). These measures are calculated from the photometric measurements and are typically published as part of a luminaire’s technical specifications. But being able to fully describe the link between the perceived light attributes, physical light characteristics, and technology variables is still insufficient to describe the overall light quality because critical application knowledge is missing. For example, how we perceive colors and whites depends on the application and the observer. The goals and requirements for illuminating an office space, for example, differ significantly from the goals and requirements of illuminating a fashion store. Also, the observers’ preference and adaptation state will play an important role. A lighting designer for example will always choose high-quality lighting components, but the designer’s artistry and expertise to create a lighting solution that is appropriate for the space being illuminated is equally important for a successful design. This gives the users of the space the high-quality experience that they expect and desire.


    Furthermore, like most of the new technologies, solid-state lighting also provides new possibilities to differentiate in quality of light like fast temporal response, multi-primary control, and small form factor, but also introduces some unwanted visual effects that were absent or less dominant for the conventional, well-established, lighting technologies.

    Coordination and conversation

    Quality of light isn’t one specific easy-to-define term, but rather a coordination of several different but related considerations. The technical measurements of light output is only one consideration: quality of light also entails the goals and requirements of specific applications, and may even take into account the age of people in the lit environment, and the data and services that the users and managers of illuminated spaces need.

    As always, the ultimate objective is to specify and deploy the right solution for a customer. Because there is no one-size-fits all approach to quality of light, lighting professionals must enter into a conversation with customers to design one-of-a-kind lighting solutions that address the specific needs of the people who manage and experience them.

    And that conversation will continue to expand and grow. New approaches to connected lighting are adding further non-visual considerations to quality of light. By bringing digital lighting and information technology together, connected lighting systems can gather and share in-context information, creating a platform for Internet of Things applications. The flow of data enabled by a connected lighting system delivers new insights, benefits, and experiences to both the users and managers of illuminated spaces. Quality of light becomes more personalized and situational, changing depending on who is present and what their needs are—whether it’s directions to a specific item on the shelf of a supermarket, the ability to adjust the lighting over a desk in an open-plan office, or a way of continuously monitoring the noise level on the streets of a city.


    Click here to download the full white paper on quality of light and how certain characteristics need to be revisited in the era of Ledification.