Munsell System of Colour Notation

There are, more or less, six billion people in the world and each and every one of them has different name or explanation of one exact colour. In other words, they will never understand each other speaking of a colour, unless there is unification or just a simple formula, instead of a name for the colours. The same conclusion has made Albert H. Munsell nearly a century ago.

Artist by profession, Professor Munsell wanted to create a “rational way to describe colour” that would use decimal notation instead of colour names (which he felt were “foolish” and “misleading”), which he could use to teach his students about colour. He first started work on the system in 1898 and published it in full form in “A Color Notation” in 1905.

Despite the fact that they were quite a few other scientists trying to place all colours in a three dimensional colour solid of one form or another, none of them succeed to do that. But how did Munsell succeed then? There is only one difference between the Munsell colour system and the rest ones – the first is based on a firm experimental scientific basis. Whereas the rest of the systems remained either purely theoretical or encountered practical problems in accommodating all colors.
Due to his experiments, the American artist was the first to separate hue, value, and chroma into perceptually uniform and independent dimensions, and was the first to systematically illustrate the colours in three dimensional space.

The Munsell colour system as known nowadays consists of three dimensions as folows:

•    HUE (“The quality by which we distinguish one color from another, as a red from a yellow, a green, a blue or a purple.,” explained Albert Munsell)
•    VALUE (“The quality by which we distinguish a light color from a dark one.”)
•    CHROMA (the purity of a colour in a relationship with white, gray, and black)
Hue.

The hues are represented in a circle which follows the natural colour order- R, Y-R,Y, Y-G, G, B-G, B, B-P, P, R-P (except of the Orange, presented as Red-Yellow). Each of the primary (R, Y, B), secondary (R-Y, G, P) and tertiary (Y-R, Y-G, B-G, B-P, R-P) colours is separated in ten increments and is given a number from 1 to 10 for each different hue of that particular colour. The primary, secondary and tertiary hues have number 5 in front of the colour letter. The rest of the hues are identified by changing the number 5. For example, 5R is pure red, 4R is the next hue closer to R-P, e.g. 4R is more purple but 6R is closer to R-Y, e.g. 6R is more yellow. Now, the scope of the Munsell system has 100 hues (10 primary, secondary and tertiary and 10 different hues for each of them).

When a new hue is found, despite the already stated numbers of the hues, we use decimals in the notation- 4.2 P-R, 6,7 B-P, ect.

Value.

The circle with hues is placed around a cylinder divided from 0 for Black to 10 for White and 1-9 are variations for Grey. This cylinder represent the Value of the colours and is identified by number from 0 to 10 followed by an oblique stroke 2/, 3/ etc. When the circle with hues moves up and down around this cylinder, each of the hue gets mixed with black, white or different greys. The lighter the grey, the lighter the hue is and vice versa. That is how the light and dark colours are formed.

Chroma.

The quantity of black, white or grey from the value cylinder mixed with one hue determines the chroma or purity of colours. The more black, white or grey, the lower the chroma is and vice versa. The dimension of chroma is perpendicular graduation to the value cylinder, starting from the greyest hue of a colour (closest to the value cylinder) until it reaches the highest chroma of hue (when no grey, black or white added). The chroma is presented with an oblique stroke and number after it: /1, /2, /3 etc. As we can see, the chroma does not have a specified limit. Thus, if a brighter hue is found, it is added on the same row with the following number.

Having these three dimensions in mind, and how they are notated, we can precisely identify what the colour is for any given colour formula. For instance, the formula 7Y-G 8/5 would be light and more yellowish lime green.

As we saw, the Munsell system has an irregular form opposite to the rest of the systems tried to place all colours on a three dimensional solid. In the same time, it is the only one that developed further and even outstands its contemporary colour models. The reason is that Mr. Munsell first realizes that not all the hues reach their full chroma at the same level of value, neither all the hues have the same level of chroma. These two confirm that it is impossible to use a solid to place all the colours on.  Therefore Munsell leaves the three dimensional solid as a solution and tries to classify the colours as the human eye perceives them with their tree dimensions. His own words are a confirmation of the aforementioned:

Desire to fit a chosen contour, such as the pyramid, cone, cylinder or cube, coupled with a lack of proper tests, has led to many distorted statements of color relations, and it becomes evident, when physical measurement of pigment values and chromas is studied, that no regular contour will serve.
—Albert H. Munsell, “A Pigment Color System and Notation”

The result is an open colour system giving the possibility of new hues to be added. Moreover Munsell’s formula is short and simple to use. These qualities are the key to its flexibility.

Being such a flexible colour system, many institutions around the world adopted its base to develop their own colour systems. Some of these institutions are American National Standards Institute (ANSI) to define skin and hair colors for forensic pathology, the United States Geological Survey (USGS) for matching soil colors, British Standards Institution, The German Standard Colour system and the Japanese Industrial Standard for Colour breweries for matching beer colors and many others.

Eventually, the Munsell Colour System became a unification code for colours and has been used in many other areas apart from the interior design: education, geology, industrial product development, archaeology, environmental studies, food production, government standards and safety.

Sources:
http://www.glenbrook.k12.il.us/gbssci/phys/Class/light/u12l2e.html
http://www.applepainter.com/Chap04/
http://www.handprint.com/HP/WCL/color7.html#MUNSELL
http://en.wikipedia.org/wiki/Munsell_color_system