Light and Colour Theories, and their relation to light and colour standardization

by Joseph W. Lovibond

Their positions in the scales correspond.

Their unit divisions are equal in number, and in dimensions.

Their colour positions correspond, when an artificial tintometrical spectrum is made by regularly overlapping monochromes.

It follows that when the two scales are superimposed as in Plate V., showing similar monochromes as lying in the same perpendicular, the same wave length numbers apply to both; concerning the dimensions between the monochromes, the spaces occupied by 72,716 wave lengths between the spectrum monochromes, also represent similar spaces in the tintometrical scales, and one-twentieth of this 3,635 represents the space of a single unit in each case.

In connexion with these co-related dimensions, some information is obtainable bearing on the limitation of a monochromatic vision for discriminating small colour differences. Under ordinary daylight conditions, the unit in the lighter shades of the tintometrical scale is divided into 100 fractional parts, each fraction therefore represents a space occupied by thirty-six wave lengths in the spectrum scale. This may be near the limit of dimension for monochromatic vision in such a gradually changing colour scale, as that of the spectrum, and may be some guide as to suitable slit areas in the synthetical building up of complex coloured light.

PLATE VI
SIX COLOUR CHARTS IN ONE OR ANOTHER OF WHICH ANY SIMPLE OR COMPLEX COLOUR FINDS A DEFINITE POSITION.

To face page 39.[Lovibond, Colour Theories.