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Perception of electric light sources of different colour properties

An analysis of the experimental conditions by which V(λ) was determined suggests that it cannot account fully for the human response to light. Much experimental work has shown a discrepancy between luminance measurement and brightness perception. Experiments have been carried out to assess the visual perception of various fluorescent and sodium lamps. Two lamps are presented simultaneously in adjacent light booths. Observers are asked to balance the two for visual equality. Results have shown that a significant difference in illuminance is needed to match lamps of different spectral distribution for visual equality. Lamps of higher colour quality require lower illuminance than do lamps of poorer colour quality. The majority of observers expressed a preference to work in the booth illuminated by the source of higher colour quality, despite a significantly lower illuminance. The results are supported well by previous experiments on visual clarity.