Investigations of the subjective balance between illuminance and lamp colour properties

The paper reports two experiments concerned with the balance between illuminance and lamp colour properties for equal satisfaction with visual appearance. The first demonstrates the existence of this balance over a wide range of interior colourfulnesses. An explanation, based on the influence of lamp type and illuminance on the saturation of colours in an interior is proposed, which suggests that Colour Discrimination Index should be a better predictor of the magnitude of the balance than Colour Rendering Index. To test this suggestion the second experiment was designed, using both coloured and achromatic interiors. The results for the coloured interior support the earlier study and lead to the conclusion that Colour Discrimination Index is a better predictor. The results for the achromatic interior are of a different nature.