Effect of correlated colour temperature on the perception of interiors and colour discrimination performance

Abstract

A feature of many national lighting standards is the recommendation that lamps with high correlated colour temperatures should not be used at low illuminances. The technical justification for this advice is limited so two experiments have been conducted to explore its validity. In the first experiment, fifteen observers carried out colour discrimination tasks and assessed the lighting of a small room lit to different illuminances using lamps with good colour rendering properties but with different correlated colour temperatures. The room decor was achromatic but natural colour, in the form of fruit and flowers, was introduced as another variable. In the second experiment, ten observers carried out colour discrimination tasks and made assessments of the lighting of the same room lit to 225 lx, but decorated with blue or pink walls and lit by lamps with good colour rendering properties but different correlated colour temperatures. Again, natural colour, in the form of fruit and flowers, was introduced as another variable. Analyses of the assessments of the lighting of the room showed that one major factor determining the impression given by the lighting was the illuminance. Increasing the illuminance made the lighting of the room appear more pleasant, more comfortable, clearer, more stimulating, brighter, more colourful, more natural, more friendly, more warm, more uniform, less hazy, less oppressive, less dim and less hostile. The correlated colour temperature of the lamps used had virtually no effect on the observer's impression of the lighting of the room. The other major factor influencing the impression of the lighting of the room was the presence of natural colour. Introducing natural colour, in the form of fruit and flowers, enhances the positive impressions created by the lighting, particularly at the higher illuminances. This enhancement occurs regardless of the correlated colour temperature of the lamps being used. It can be concluded that the advice limiting the use of high correlated colour temperature lamps in rooms lit to low illuminances is unnnecesarily restrictive. The results obtained suggest that provided the occupants are fully adapted to the lighting the correlated colour temperature of the lamp has little effect on people's impressions of the lighting of the room.