Sight is the sense that gives us visual information about the world around us, and light is a prerequisite for this process. Light radiation can be measured physically with precision, but light as the experience created when light rays strike the retina of the eye is sensual, and thus both subjective, relative and complex. Like all impressions that reach our different senses, the visual experience of the outside world is created through processes that can be described from the basis of sensory, biology, physiology, perception, cognition and emotion. These processes cannot be translated into physical terms. We can measure stimuli that reaches the retina, but this gives very limited information about the experience.In the beginning, when all life existed in the sea, some organisms developed cells that were sensitive to light, allowing them to orient themselves to brighter or darker areas. This early capacity for visual information produced blurred visual impressions, only detecting differences between contrasts. Eventually, more advanced life forms developed the sharp central vision which, according to one hypothesis, appeared during a period when life had evolved into a predator prey interaction. Both these visual abilities, the blurred peripheral vision and the detailed focus vision are represented in the human sense of sight, and the blurred peripheral vision is crucial for our visual experience of the room.All the light we see is reflected from surfaces, unless you look directly into a light source. The properties of surfaces, their colour and texture in combination with the properties of the light source and the distribution of the light is what provides visual information about the room. It is through the modelling and interaction of light and colours that the experience of the room can appear with its shapes and textures, proportions, dimensions, depth and spatiality.Since electric light was introduced in our built environments about 100 years ago, light quality has been evaluated and regulated based on physical measurements, which are correlated to the human eye’s ability to register light and colour. International lighting standards for spatial environments provide detailed recommendations for light levels described in Lux or Footcandle. These measurements are based on the focus vision, which require higher light levels to function optimally. But the measurements do not provide information about the properties of the reflected light, which is what we see, nor does it include one of the basic functions of the sense of sight, which is to react and respond to contrasts.The beverage and food industries have for many years used terminologies and concept models that describe sensory properties of various products. The underlying methodology is called Sensory Analysis which is established in several different areas. Within the interdisciplinary research project Perceptual Metrics for Lighting Design, we have developed methods to measure perceived light quality for both light sources, luminaires and spatial environments with inspiration from Sensory Analysis. The project has been developed with a practice based and design-oriented approach,in close collaboration with the lighting industry. On workshops with lighting designers, we have collected words that describe the perceived character of light, shadows and contrast, and through repeated studies been able to develop the basis for a terminology to give value or measure perceived light quality in spatial contexts. An interesting and important aspect that has become apparent during the course of this project is how much light, shadows and contrasts affects the atmosphere of environments.The lecture will give an overview of the human visual perception in relation to how we perceive spatial environments, and also a description of the Perceptual Metrics for Lighting Design method and how it may be used in practice and research.

The use of luminous colors is increasing in design and art due to new technologies in color-tunable lighting. Our project addresses the lack of guidance when working with additive mixing of luminous colors, including their interaction with surface treatments. When using paint colors, designers and artists can draw from theories developed by both color scientists and artists/designers.

However, the same is not yet true when working with additive mixing of colored light, which LED technology only recently made possible. The project’s overall scope was to explore and identify various aspects in the use of luminous colors from a perception-based perspective, and to develop and propose a basis for a perception tool box for practitioners.

Nowadays, lighting planning is predominantly determined by the need to meet physically measurable requirements that are often based on current lighting standards. However, meeting the minimum technical requirements of the standards is no guarantee for a visually appealing light environment. Instead, requirements based on perceived light qualities also need to be included to achieve better user comfort. Taking perception-based qualities into consideration when creating a light environment is, for many, not an easy task. In addition, a common terminology for perceived light qualities is currently lacking, both in industry and in research. The aim of this paper is, therefore, to explore how perceived light qualities of white light sources can be described when employing user-centric measures. The focus was on the qualities of light colour and diffuse and distinct light since these qualities have a great impact on the visual impression of light. The perception was assessed by applying analytical sensory analysis to lighting products, a method found to be promising in previous work. The methodology is based on analytical measurement by the human senses, which is particularly valuable when developing a general terminology. Since sensory analysis is still quite new to the topic of lighting, the applicability of using the methodology to assess lighting in a real context was also investigated. The results of the studies showed that the perception of light qualities can be described using further concepts in addition to those currently used. For light colour, the concepts of reddish, bluish, yellowish, and greenish light colours proved suitable for providing a richer description of the quality. The concepts of diffuse and distinct light satisfactorily captured variations in light contrast produced by shadows, reflections, and sparkles. In addition, the studies revealed that analytical sensory analysis was applicable for assessing the perception of lighting in a real-world context. The latter means that knowledge gained in the laboratory can be translated into real environments. The user-centric measures investigated in this paper have contributed to the terminology related to perceived light qualities. These can complement the physical measures in lighting planning to promote light environments that are not only energy efficient and meet technical requirements, but also cater for increased user comfort. © 2023 by the authors.

Perceived light qualities of lighting products are generally insufficiently described, reflecting that perception-based qualities, such as light colour, are not considered to the same extent as physical measures when creating light environments. It is well known that perceptual impressions are affected by, and relative to, surrounding stimuli. To develop descriptions of perceived light colour of white light sources, new concepts were evaluated in a pilot study combining paired comparison tests and descriptive sensory analysis. The findings confirmed that the perception of light colour is relative, demonstrated by cool light sources being perceived as warm/yellowish/reddish in relation to other cool light sources – which was well captured by the combined sensory methods with simultaneous light sources. The newest concepts, cyanish and magentaish light colour, were found to be useful in describing the perceived differences, showing that more concepts than warm, neutral and cool are needed for a richer description of light colour.