seminal system ensured that ‘every colour is placed
in its proper relation to all pure elements as well as
all mixtures’ but it lacked a means of colour notation
among other problems. By splitting the value and the
chroma, in particular, Munsell ensured that all the
colours on a latitudinal plane had the same value.
Pictorially, Munsell’s three dimensions are often shown
as a wheel with a rim of hues, an axle of values and
chroma spokes appearing to be spaced evenly, because
it is tuned to Munsell’s careful record of the human
visual response to colour. The Munsell Colour Space
is also, and better, described as a tree with hue leaves, a
value trunk and rigorously adjusted chroma branches.
Within this framework each specific colour stimulus
is denoted by a three-part coordinate comprising
hue, value/chroma or H/V/C. Under this system,
which was revised or ‘renotated’ in 1943, a red with
medium lightness and a fairly high chroma would be
recorded as 5R 5/10 while 5P 4/8 would be a purple
with a value of four and chroma of eight, for example.
Cosmic latte is 7.5Y 10/2 – or thereabouts.
The colour atlas is easy to read and yet, in the 1930s,
the American physicist Deane Brewster Judd found
that no matter how he adjusted the Munsell units for
hue and chroma to give them the same magnitude,
the resulting diagram always lost its uniformity, a
phenomenon Judd called hue superimportance.
However, the Munsell system has limitations. In
particular, its discrete samples of colour are separated
by relatively large gaps, making it hard to measure a
threshold just-noticeable difference (JND). Although
in 1950, the number of hues in the Munsell Book of ▼
A Color Sphere appeared on the frontispiece
of Albert Munsell’s 1905 pamphlet A Color Notation