Color Theory: How to convert Munsell HVC to RGB/HSB/HSL
- by Ian Boyd
I'm looking at at document that describes the standard colors used in dentistry to describe the color of a tooth. They quote hue, value, chroma values, and indicate they are from the 1905 Munsell description of color:
The system of colour notation
developed by A. H. Munsell in 1905
identifies colour in terms of three
attributes: HUE, VALUE (Brightness)
and CHROMA (saturation) [15]
HUE (H): Munsell defined hue as the
quality by which we distinguish one
colour from another. He selected five
principle colours: red, yellow, green,
blue, and purple; and five
intermediate colours: yellow-red,
green-yellow, blue-green, purple-blue,
and red-purple. These were placed
around a colour circle at equal points
and the colours in between these
points are a mixture of the two, in
favour of the nearer point/colour (see
Fig 1.).
VALUE (V): This notation indicates the
lightness or darkness of a colour in
relation to a neutral grey scale,
which extends from absolute black
(value symbol 0) to absolute white
(value symbol 10). This is essentially
how ‘bright’ the colour is.
CHROMA (C): This indicates the degree
of divergence of a given hue from a
neutral grey of the same value. The
scale of chroma extends from 0 for a
neutral grey to 10, 12, 14 or farther,
depending upon the strength
(saturation) of the sample to be
evaluated.
There are various systems for
categorising colour, the Vita system
is most commonly used in Dentistry.
This uses the letters A, B, C and D to
notate the hue (colour) of the tooth.
The chroma and value are both
indicated by a value from 1 to 4. A1
being lighter than A4, but A4 being
more saturated than A1. If placed in
order of value, i.e. brightness, the
order from brightest to darkest would
be:
A1, B1, B2, A2, A3, D2, C1, B3, D3,
D4, A3.5, B4, C2, A4, C3, C4
The exact values of Hue, Value and
Chroma for each of the shades is shown
below (16)
So my question is, can anyone convert Munsell HVC into RGB, HSB or HSL?
Hue Value (Brightness) Chroma(Saturation)
=== ================== ==================
4.5 7.80 1.7
2.4 7.45 2.6
1.3 7.40 2.9
1.6 7.05 3.2
1.6 6.70 3.1
5.1 7.75 1.6
4.3 7.50 2.2
2.3 7.25 3.2
2.4 7.00 3.2
4.3 7.30 1.6
2.8 6.90 2.3
2.6 6.70 2.3
1.6 6.30 2.9
3.0 7.35 1.8
1.8 7.10 2.3
3.7 7.05 2.4
They say that Value(Brightness) varies from 0..10, which is fine. So i take 7.05 to mean 70.5%.
But what is Hue measured in? i'm used to hue being measured in degrees (0..360). But the values i see would all be red - when they should be more yellow, or brown.
Finally, it says that Choma/Saturation can range from 0..10 ...or even higher - which makes it sound like an arbitrary scale.
So can anyone convert Munsell HVC to HSB or HSL, or better yet, RGB?
