Colour Rendition and Museum Lighting

Abstract

CONSIDER first two sources of light, on the ~ne hand da~light, on the other mercury lIg!lt (as used In nlany street lighting installatIons). UI~der illumination from mercury lamps. practIcally everything, be it picture, advertlselne!lt, ~r hu~naI~ face, looks wrong. l!nder ~aylIght .Illu~natlon everything looks ngl:t, Indeed IS aXlonlatically right. The maIn reason for this difference is sufficiently obvious-almost complete absence of red from mercury light. Suppose, now, that the illumination comes ~rom ad~ixtur.e of merc~ry light with daylIght. It IS agaIn an obvIous fact that if the adlnixtureof mercury light is sufficientlysmall, no one could notice it. But if the relative amount of mercury light were increased there would come a point at which its effect would becolne noticeable. The critical proportion of Inercury admixture represents the tolerance of the observer to this particular distortion ?f daylig~t. The principle of this experiment IS the baSISof our approach at the National Physical Laboratory to the problem of colour rendition.