Edinburgh Napier University

  Lighting metrics are neither absolute quantitative nor purely qualitative experiential measurements. Possibly uniquely amongst the SI system of physical measurements, the Candela is a pseudo-objective measurement based on the human visual experience. As renowned author and researcher Kit Cuttle puts it, “instead of being a physical quantity, the lumen is a psychophysical quantity”.
Both speakers have extensive experience of designing low light museum environments. These are the places where the Lumen, the very basis of our system of lighting measurements, frequently diverges from the visual brightness perceived by the viewer.
What properties do designers actually work with and are they represented in the metrics we have available to us?