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.