Colour design and non-image-forming effects in humans: An open issue

Nowadays in industrialised countries, human beings spend 80–90% of their time indoors. Under these conditions the light, the colours, ie the perceived image, differs considerably from the outdoors. But this also influences the NIF (non-image-forming) effects on our nervous system, such as regulation of the circadian rhythm and other physiological effects. The risks to health arising from NIF effects are highlighted. Even though extensive neurophysiological research has demonstrated the importance of proper NIF management for human health, use of the latter is virtually absent in the design practice. Therefore, we highlight the unresolved research challenges which prevent the development of complete models, particularly useful in defining lighting and, above all, colours in indoor environments, to correctly manage NIF effects.