colour analysis of unison pastels · the pastels in each series are numbered for individual...

Colour Analysis of Unison Pastels

Paul Centore

c© February 15, 2014

Abstract

Munsell specifications, calculated from spectrophotometric measurements,are presented for Unison Colour’s complete line of 422 artist’s pastels. Thepastels’ hue, value, and chroma distributions are delineated. Tables and figuresare presented, that painters can use in making practical decisions about pastelemployment and purchases. A list of duplicates (pairs of pastels whose namesare different but whose colours agree to within a CIE DE 2000 value of 2 orless) is given.

1 Introduction

A single manufacturer typically produces a few hundred pastels, of various colours.This wide variety is necessary because, unlike paints, pastels cannot be readily mixedto produce large quantities of new colours. The variety, however, requires a significantorganizational effort from both artists and manufacturers. The current documenthelps to provide that organization for one pastel brand, Unison Colour, by analyzingtheir line of 422 colours. The analysis is performed largely in terms of the Munsellcolour system, whose concepts of hue (red, yellow, etc.), value (light vs dark), andchroma (dull vs saturated) are basic to painting. Tables and figures are presented,that should help artists select Unison pastels intelligently, both when painting andwhen purchasing. Purchasing is especially an issue for online or catalog sales, wherethe artist cannot see the pastels directly. The Unison gamut is delineated in termsof hue, value, and chroma. Several pairs of duplicates, in which two different pastelsproduce very similar colours, are also identified.

This report first describes the Unison pastel line, and then describes the Munsellsystem, which will provide rigorous terms of reference for the pastel analysis. The

1

PAUL CENTORE

analysis procedure and results are given next, including tables and figures for practi-cal use. Finally, an approach is suggested, involving contributions from painters andmanufacturers, to extend this analysis to further pastel brands

2 Description of Unison Pastels

Unison Colour has divided their complete line of 422 pastels into several series,listed in Table 1. The pastels in each series are numbered for individual reference.For example, Orange 9 is the 9th pastel in the Orange series. There are five series ofearth colours (Brown Earth, Natural Earth, Blue Green Earth, Yellow Green Earth,and Red Earth). Another seven series, that concentrate on certain hues, mightbe called spectral (Red, Orange, Yellow, Green, Turquoise, Blue Green, and BlueViolet). The Grey, Light, and Dark series are self-descriptive, containing mainlynear-neutral colours. Finally, there are some miscellaneous series, containing theAdditional, Portrait, and Special Collection series, as well as a series labeled “John’sSet” after John Hersey, Unison’s founder. Most of the series contain either 18 or 36pastels. Typically, a box set contains all the pastels from one or more series.

3 The Munsell System

Albert Munsell devised his colour specification system for painters and visual artists.It classifies surface colours by three perceptual attributes that are basic to painting:hue, value and chroma.

Hue is universally understood. It says whether a colour is red, yellow, purple,etc. Munsell designates 10 basic hues: R (red), YR (yellow-red, or orange), Y(yellow), GY (green-yellow), G (green), BG (blue-green), B (blue), PB (purple-blue),P (purple), and RP (red-purple). Each basic hue is further subdivided into 4 steps,denoted with a numerical prefix. For example, the four greens are denoted 2.5G,5G, 7.5G, and 10G. 2.5G is a yellower green, that is closer to GY than it is to BG.10G is a bluer green, that is closer to BG than it is to GY. In all, then, the Munsellsystem specifies 40 hues (4 steps for each of the 10 basic hues). These 40 hues areequally spaced perceptually. One could interpolate any desired amount between twoadjacent hues. For example, the hue 6GY is a yellowish green that is between 5GYand 7.5GY, but closer to 5GY. White, black, and greys are not considered hues inthe Munsell system. Rather, they are designated N, for “neutral.”

Many different colours can have the same hue. Figure 1, for example, showsthe “hue leaf” for 6GY, a set of colours all of which have hue 6GY. The different

c© 2014 Paul Centore 2

COLOUR ANALYSIS OF UNISON PASTELS

Series Number of PastelsAdditional 62Blue Green 18Blue Green Earth 18Blue Violet 18Brown Earth 36Dark 18Green 36Grey 36John’s Set 18Light 18Natural Earth 18Orange 18Portrait 12Red 18Red Earth 18Special Collection 18Turquoise 6Yellow 18Yellow Green Earth 18

Total 422

Table 1: Unison Pastel Series

colours within a hue leaf are specified further by value and chroma. The empty boxesindicate colours that are in the Munsell system, but that are beyond the gamut ofthe process used to produce the figure. The hue leaf shades smoothly into the neutralaxis, consisting of greys, shown on the left.

Munsell value designates how light or dark a colour is. The theoretically darkestblack has a value of 0, and is denoted N0. The theoretically lightest white has avalue of 10, and is denoted N10. Between N0 and N10 are 9 progressively lightergreys, denoted N1 through N9. The spacing between the greys is perceptually equal.All colours have a Munsell value, not just the neutrals. For example, there are lightblues and dark blues. A blue with value 8.5 has the same lightness as N8.5.

Munsell chroma refers to how intense, or saturated, a colour is. For example,a lemon is an intense yellow, while masking tape is a dull yellow. A dull colouris closer to a neutral grey than an intense colour is. The Munsell system denotes

3 c© 2014 Paul Centore

PAUL CENTORE

N2

N9

N8

N7

N6

N5

N4

N3

N1

2 4 6 8 10 12

Chroma

Hue: 6GY

Valu

e

Figure 1: The Hue Leaf for 6GY in the Munsell System

chroma numerically. Greys have chroma 0. A colour with a chroma of 10 or higher isgenerally perceived as saturated. Colours of low chroma, say 4 or less, are perceivedas subdued, with a high grey content.

The Munsell notation for a colour takes the form H V/C, where H stands forhue, V stands for value, and C stands for chroma. For example, the colour 10R 9/6would be a very light (V is 9), moderately intense (C is 6), orangish red (H is 10R).A colour with chroma 0 is a neutral grey, which is denoted NV, where V stands forvalue. For example, N5 is a grey that is midway between white and black.

The Munsell system is important to painters for two reasons. First, the attributesit identifies (hue, value, and chroma) are all vital to art. Second, the system providesa language to communicate rigorously about colour. The 1943 Munsell renotation1

has standardized the calculation of hue, value, and chroma, from objective spectralmeasurements, so that these terms can be quantified. The standardization was basedon a large number of colour judgements made by about 40 human subjects, to insurethat Munsell specifications are perceptually meaningful.



4 Analysis

4.1 General Procedure

The data set for this analysis consisted of 422 samples, kindly provided by UnisonColour in January 2014, comprising their complete line of pastels. Each samplemeasured about 3 cm by 4 cm, and had been applied by hand on white paper,in a layer that was opaque (or nearly so). The samples were measured with anX-Rite i1Pro2 spectrophotometer, using the M2 setting. The output of a spec-trophotometer measurement is a sample’s reflectances, at intervals of 10 nm, from380 to 730 nm. CIE xyY values2 were calculated for each sample, under the as-sumption of Illuminant C, which is the illuminant on which the Munsell system isstandardized.1 The 1943 Munsell renotation1 provides a look-up table from Munsellcolours to xyY coordinates. An inversion algorithm3 was used to find a Munsellspecification for each pastel, from its xyY coordinates. Tables 2 through 5 list theseMunsell specifications. For researchers who would like to continue these investiga-tions further, the reflectance spectra and the Munsell specifications are available inthe computer files UnisonPastelsReflectanceSpectra.txt and MunsellSpecifications-ForUnisonPastels.txt, respectively, at the website www.99main.com/∼centore.

Figures 2 through 11 are a sort of inverse to Tables 2 through 5. These figuresshare the same chroma and value axes that appear in Figure 1. Rather than referringto a single hue, however, each of Figures 2 through 11 refers to a range of hues, whichshare the same Munsell letter designation. Figure 2, for example, shows all pastelswhose hue is between 0R and 10R, so a pastel of hue 3.2R could appear alongside apastel of hue 9.6R. The pastels in the figures are denoted by obvious abbreviations,given in Table 6. Each pastel in a figure is placed at coordinates given by its chromaand value, as in Figure 1. If multiple pastels with the same hue letter designation(but not necessarily the same numerical hue prefix) also have the same chroma andvalue, then those pastels are displayed in a sequence, separated by slashes.

Painters can use Figures 2 through 11 to determine which Unison pastels have, atleast approximately, the desired hue, value, and chroma. Informed choices can thenbe made when executing a painting. In addition, the figures can aid in purchasingdecisions. Typically, colour reproductions in art supply catalogs, either in paper oronline, are not accurate enough for confident purchasing decisions, especially giventhe wide gamut pastels can cover. The figures should provide a better basis for anartists to decide which pastels will be most helpful.


PAUL CENTORE

Brown Earth Natural Earth Blue Green Earth1 0.9Y 7.8/2.5 1 3.9YR 3.5/6.1 1 7.2G 7.8/1.62 2.6Y 7.0/2.5 2 6.6YR 3.7/4.0 2 7.2BG 7.2/2.43 0.4Y 6.6/3.6 3 5.1YR 5.7/6.2 3 4.7BG 6.3/2.64 9.7YR 5.4/4.1 4 8.9YR 6.7/6.1 4 1.2BG 5.8/2.95 8.2YR 3.6/2.9 5 9.1YR 7.2/7.5 5 6.7BG 4.7/3.06 1.2YR 2.7/1.9 6 6.1YR 7.1/6.7 6 2.8B 2.9/3.97 9.5YR 8.4/3.2 7 7.2YR 2.8/3.0 7 7.2G 7.0/2.58 6.9YR 7.4/5.1 8 9.9YR 3.9/3.5 8 3.7G 6.4/3.09 5.5YR 6.8/6.2 9 0.6Y 5.1/3.4 9 0.9BG 5.2/3.7

10 3.8YR 6.2/6.4 10 9.9YR 5.2/4.3 10 4.5BG 4.8/4.611 3.2YR 4.9/7.0 11 5.6YR 5.3/4.1 11 8.8BG 4.1/4.112 5.8YR 3.9/6.1 12 6.0YR 6.4/4.8 12 8.0BG 3.5/4.413 9.7YR 7.7/2.9 13 9.5YR 7.7/5.4 13 5.0GY 7.9/2.714 9.6YR 7.0/4.1 14 9.4YR 6.9/4.2 14 3.7GY 7.1/2.615 7.0YR 6.1/4.3 15 0.6Y 6.6/3.6 15 6.5Y 6.1/2.616 3.4YR 5.6/5.0 16 8.6YR 6.8/2.7 16 9.3Y 5.2/1.917 4.9YR 4.3/4.0 17 0.8Y 7.6/2.2 17 7.7Y 4.0/1.818 6.4YR 3.2/3.8 18 0.9Y 7.7/2.9 18 2.2G 3.6/1.919 7.2YR 8.5/1.920 6.9YR 7.5/2.4 Yellow Green Earth Red Earth21 1.0YR 6.1/3.2 1 6.0Y 7.9/1.4 1 9.4R 8.2/3.222 1.2YR 5.2/3.5 2 8.4GY 7.6/1.7 2 6.8R 7.5/4.223 2.4R 4.0/3.9 3 9.0GY 7.0/2.1 3 7.8R 6.5/4.824 4.7R 3.0/3.2 4 0.4G 6.2/1.6 4 8.2R 5.6/5.825 1.2Y 7.9/5.0 5 0.6G 5.4/2.5 5 8.2R 4.9/6.626 10.0YR 7.4/4.6 6 6.0G 4.5/2.8 6 8.4R 2.9/4.427 0.6Y 5.9/4.7 7 5.2Y 7.9/6.5 7 0.7YR 7.8/4.728 6.5YR 4.9/5.2 8 6.6Y 7.3/6.7 8 9.5R 7.0/6.029 9.6YR 4.2/4.0 9 0.6GY 6.8/6.6 9 0.1YR 6.0/8.430 3.0YR 3.6/4.4 10 9.2Y 5.6/7.5 10 9.7R 5.2/8.031 3.1Y 8.3/2.9 11 3.9Y 4.9/6.1 11 0.4YR 4.0/8.832 4.7Y 7.1/3.1 12 1.9Y 4.6/6.0 12 8.1R 3.4/6.733 3.9Y 5.7/3.1 13 3.4Y 8.2/4.3 13 4.3YR 8.3/3.234 6.0Y 5.0/3.1 14 7.3Y 7.6/3.7 14 3.1YR 7.3/6.035 2.1Y 3.8/2.8 15 5.7Y 7.0/4.7 15 1.4YR 5.7/6.036 0.4Y 3.1/2.6 16 5.4Y 5.9/4.8 16 9.5R 4.8/5.8

17 6.8Y 4.8/3.9 17 2.7YR 3.9/6.318 10.0GY 3.8/2.5 18 1.2YR 3.2/5.5

Table 2: Munsell Specifications for Unison Earth SeriesPastels



Green Red Orange Yellow1 9.5G 3.4/3.7 1 7.8R 3.6/9.0 1 9.9R 4.8/12.3 1 8.2YR 5.2/9.22 9.2G 4.5/4.9 2 7.6R 4.7/12.2 2 8.6R 5.0/15.0 2 0.2Y 6.4/9.63 5.2G 5.4/3.2 3 8.9R 5.9/12.1 3 9.8R 6.0/14.4 3 2.5Y 6.9/10.04 8.2GY 6.7/2.9 4 0.5YR 6.3/11.3 4 9.0R 6.3/12.3 4 6.2Y 8.4/8.05 9.2GY 7.5/2.9 5 8.6R 6.9/9.3 5 9.0R 6.5/11.3 5 7.1Y 8.9/5.76 6.9GY 8.2/2.9 6 8.4R 7.3/7.6 6 8.3R 7.9/6.2 6 9.9Y 9.1/4.57 4.1G 4.1/6.1 7 5.4R 3.2/9.1 7 1.8YR 6.1/15.7 7 4.8YR 6.6/13.28 1.1G 4.6/5.6 8 6.1R 3.5/10.9 8 3.8YR 6.7/15.6 8 7.8YR 7.3/12.09 2.0G 5.6/5.5 9 6.8R 5.1/12.2 9 4.0YR 7.1/13.0 9 0.2Y 7.6/12.8

10 6.5GY 5.9/6.8 10 5.7R 5.8/10.7 10 4.0YR 7.5/10.3 10 3.5Y 8.5/9.911 5.5GY 7.3/7.5 11 5.6R 6.8/8.5 11 4.4YR 8.0/7.6 11 4.5Y 8.8/7.012 2.9GY 8.2/6.1 12 5.8R 7.4/6.7 12 5.0YR 8.4/5.2 12 6.5Y 9.0/4.713 1.6G 3.2/2.5 13 2.5R 2.9/6.2 13 4.8YR 6.7/14.7 13 6.2YR 5.7/10.714 5.7GY 4.2/4.2 14 9.1RP 3.1/6.1 14 6.9YR 7.4/15.6 14 6.1YR 6.5/10.215 2.0GY 5.0/6.1 15 7.3RP 3.9/8.1 15 7.3YR 7.7/11.9 15 8.4YR 6.9/9.416 7.5GY 5.8/4.5 16 8.7RP 5.4/8.2 16 7.4YR 7.9/9.6 16 1.2Y 7.3/8.017 2.4GY 7.3/6.5 17 9.2RP 6.5/7.2 17 8.0YR 8.3/7.6 17 1.5Y 8.3/5.818 6.1Y 8.1/3.6 18 9.2RP 7.4/5.2 18 7.9YR 8.6/4.3 18 2.4Y 8.8/3.719 2.6BG 4.0/5.520 7.4G 5.3/6.1 Turquoise Blue Green Blue Violet21 9.2G 5.9/5.5 1 8.2BG 4.5/6.6 1 9.4B 3.2/5.6 1 3.8P 8.4/2.722 3.8G 6.9/4.8 2 0.1B 4.9/7.4 2 2.9PB 4.2/9.3 2 0.9P 7.5/4.823 4.4G 7.6/3.6 3 9.7BG 5.6/7.8 3 2.7PB 5.8/9.5 3 2.5P 6.9/6.724 2.9G 8.1/2.8 4 0.5B 6.2/7.3 4 9.8B 7.2/5.7 4 9.2PB 6.0/8.825 1.0G 4.2/5.9 5 0.3B 7.3/6.5 5 9.7B 7.8/4.5 5 1.0P 4.1/7.526 7.8GY 5.4/8.4 6 2.6B 7.8/5.5 6 8.5B 8.7/2.2 6 4.6P 3.3/3.627 8.0GY 6.3/9.2 7 7.2B 4.1/8.2 7 5.1PB 8.6/2.228 6.0GY 7.1/9.5 8 5.1B 5.0/8.3 8 3.2PB 8.0/4.129 3.3GY 7.6/10.2 9 7.5B 6.4/8.0 9 4.2PB 7.0/7.530 3.4GY 8.4/8.7 10 4.3B 7.3/6.4 10 6.5PB 5.9/11.231 7.0GY 4.4/5.3 11 6.0B 7.9/4.3 11 7.2PB 4.8/13.232 5.5GY 5.1/6.4 12 4.8B 8.5/2.8 12 7.3PB 4.4/14.833 3.0GY 6.1/8.3 13 2.6B 4.0/6.6 13 9.6B 7.8/2.334 0.1GY 7.6/8.8 14 1.6B 4.6/6.6 14 4.7PB 7.0/5.335 1.0GY 8.5/8.6 15 1.5B 5.8/5.8 15 6.7PB 6.0/5.536 1.2GY 8.9/5.8 16 0.9B 7.3/5.2 16 8.3PB 4.7/5.6

17 2.9BG 7.9/2.8 17 4.7PB 3.8/6.318 2.0G 8.5/1.7 18 5.3PB 2.7/6.8

Table 3: Munsell Specifications for Unison Spectral Pastels


PAUL CENTORE

Grey Dark1 5.1Y 3.8/0.8 1 1.0YR 3.1/4.32 2.2BG 4.8/0.9 2 9.3R 2.7/3.53 9.2GY 6.2/1.6 3 4.2YR 2.7/2.24 2.8BG 6.6/1.3 4 5.9YR 3.1/2.95 7.8G 7.2/1.1 5 1.8Y 2.9/1.36 7.2Y 8.2/0.9 6 6.3Y 3.6/2.37 1.9P 4.1/2.9 7 8.5BG 2.7/1.88 7.3PB 5.2/2.8 8 2.0BG 2.8/2.89 4.7PB 6.2/3.2 9 4.8G 3.8/2.3

10 6.0PB 7.4/2.2 10 1.6G 3.4/3.411 1.8PB 7.9/1.8 11 6.8GY 3.8/4.112 6.3G 8.2/0.6 12 1.1GY 3.8/3.513 0.1Y 2.2/0.7 13 9.4PB 2.7/4.114 9.6B 3.5/1.2 14 7.2P 3.3/1.415 2.2PB 5.3/1.2 15 0.4B 2.5/2.516 2.7PB 6.5/0.4 16 8.8B 1.9/1.917 0.7Y 7.8/0.1 17 5.1PB 2.7/0.918 4.0Y 8.5/0.1 18 3.8PB 2.0/4.219 1.0Y 5.5/4.920 0.9Y 5.8/5.6 Light21 2.4Y 6.7/5.0 1 9.1YR 9.4/0.822 2.7Y 7.6/4.8 2 3.9Y 9.2/3.723 2.7Y 8.3/3.7 3 4.6Y 9.2/4.024 1.6Y 8.7/3.0 4 8.2YR 9.1/3.225 3.2Y 8.7/2.2 5 5.7YR 8.9/3.226 2.8Y 9.2/1.5 6 9.7R 8.7/3.427 4.5Y 9.3/2.5 7 8.6R 8.8/2.828 0.4Y 9.4/0.5 8 3.0R 8.4/2.929 1.5GY 8.7/1.3 9 2.7R 8.1/2.830 3.4GY 8.2/0.9 10 6.2RP 8.6/2.431 1.1G 7.9/1.0 11 3.8RP 9.0/2.232 9.0BG 6.8/2.0 12 0.2RP 9.1/1.033 7.2B 6.2/2.8 13 6.6P 8.6/2.034 4.2B 4.8/2.2 14 4.8PB 8.9/1.735 6.1B 3.4/0.8 15 8.9BG 8.8/1.336 8.5B 2.1/0.3 16 3.9BG 9.2/0.9

17 3.6G 9.1/0.818 2.5G 9.0/1.1

Table 4: Munsell Specifications for Unison Grey, Dark, and Light Pastels



Additional (1-38) Additional (39-62) Special Collection1 4.5PB 8.6/2.2 39 1.7Y 4.3/1.7 1 0.4YR 6.1/15.42 7.7B 8.4/2.5 40 0.9Y 5.7/1.8 2 2.6YR 6.6/13.33 2.8BG 8.4/1.1 41 0.6Y 7.2/1.7 3 3.4YR 5.3/11.14 6.3P 8.2/3.4 42 2.9Y 8.1/1.1 4 1.4YR 4.8/10.05 0.3RP 8.0/3.8 43 3.6BG 2.7/1.6 5 9.9R 4.4/9.86 5.2RP 7.2/5.1 44 9.2G 4.0/1.3 6 8.3R 4.3/11.57 2.3Y 9.1/3.3 45 7.0G 5.1/1.3 7 2.4R 3.5/8.18 2.7Y 8.9/5.3 46 0.7G 6.2/1.1 8 6.4RP 3.7/5.39 1.2Y 8.2/10.1 47 8.1GY 7.5/1.0 9 5.4RP 2.8/4.9

10 7.6Y 9.1/8.6 48 6.2G 8.0/1.0 10 9.2P 4.3/7.611 4.7Y 8.8/10.0 49 8.6B 1.9/1.9 11 2.3P 3.7/6.212 3.0Y 8.4/14.0 50 0.1PB 2.4/2.9 12 8.8PB 4.4/12.013 4.0YR 7.0/15.9 51 9.1B 3.7/3.6 13 4.8PB 4.8/12.014 9.5R 5.7/15.7 52 9.9B 5.2/4.4 14 7.4B 3.8/7.215 7.7R 4.6/13.8 53 8.7B 7.1/3.0 15 3.5B 4.1/5.016 0.1YR 5.5/12.3 54 8.3B 8.1/2.0 16 5.0BG 3.9/3.817 9.1R 5.8/10.6 55 8.4RP 5.7/5.6 17 5.8GY 3.5/2.018 4.9R 5.6/8.4 56 5.7RP 5.8/4.1 18 9.0Y 3.4/2.519 2.7YR 7.9/1.7 57 8.3P 5.2/3.520 3.4YR 7.3/1.6 58 1.6RP 4.2/3.5 John’s Set21 3.0YR 6.6/2.2 59 6.5P 6.6/4.9 1 9.3R 3.9/8.022 2.0YR 4.9/2.8 60 1.8P 6.2/4.3 2 7.5R 5.1/8.723 3.6YR 3.9/2.5 61 8.2PB 6.3/7.8 3 3.0R 5.1/8.724 3.5YR 2.9/2.5 62 3.9PB 6.3/9.2 4 8.4R 5.8/10.925 5.5YR 7.7/1.2 5 1.8YR 6.9/12.426 6.2YR 6.7/0.7 Portrait 6 7.8YR 8.1/9.327 1.8YR 5.1/2.6 1 2.7YR 7.7/6.4 7 5.2R 5.1/7.728 3.7R 3.9/2.8 2 4.8YR 7.9/7.4 8 5.9RP 5.3/6.629 6.7RP 3.0/2.7 3 0.6YR 7.7/7.7 9 5.9PB 5.8/6.830 4.5P 2.6/2.4 4 4.7YR 8.1/7.6 10 3.5PB 5.8/8.731 7.0P 8.1/2.0 5 1.2YR 8.4/4.7 11 7.5PB 7.1/6.232 3.2P 7.4/2.1 6 3.3R 5.0/9.2 12 6.5PB 7.8/4.533 3.4P 6.6/2.4 7 5.0R 4.5/11.6 13 1.3G 6.5/3.934 3.9P 5.1/3.4 8 5.8R 3.1/7.0 14 4.2B 5.9/5.135 7.0P 4.2/3.1 9 8.5RP 3.8/6.9 15 2.9B 3.9/2.836 0.6RP 3.4/3.1 10 6.2RP 6.7/5.9 16 6.6BG 6.1/3.837 1.5GY 2.5/1.1 11 3.1RP 7.6/2.4 17 2.1G 5.5/1.538 1.2Y 3.4/1.7 12 8.0R 6.9/6.1 18 8.7B 5.8/5.4

Table 5: Munsell Specifications for Remaining Unison Pastels


PAUL CENTORE

Abbreviation Unison Series NameA Additional

BE Brown EarthBG Blue Green

BGE Blue Green EarthBV Blue Violet

G GreenJ John’s Set

NE Natural EarthO Orange

Port PortraitR Red

RE Red EarthSC Special CollectionT TurquoiseY Yellow

YGE Yellow Green Earth

Table 6: Abbreviations in Figures 2 through 11



2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Munsell

Valu

e

Munsell Chroma

RE1

RE2

RE3

RE4

RE5

RE6

RE8

RE10

RE12

RE16

BE23

BE24

R1

R2

R3

R5

R6

R7

R8

R9

R11

R12

R13

O1

O2

O3

O4

O5

O6

Dark2

Light6Light7

Light8

Light9

Port6

Port7

Port8

Port12

A14

A15

A18

A28

SC5SC6

SC7

J1

J7

BE8/BE26

A17/R10/J4

J2/J3

Figure 2: Unison Pastels of Munsell Hue R


PAUL CENTORE

2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Munsell

Valu

e

Munsell Chroma

NE1

NE2

NE4

NE5NE6

NE7

NE8

NE11

NE12

NE13

NE14NE16

RE7

RE9

RE11

RE13

RE14

RE18

BE4

BE5

BE7

BE9

BE10

BE11

BE13

BE14

BE15

BE16

BE17

BE18

BE19

BE20

BE21

BE28

BE29

BE30

R4

O8

O9

O10

O11

O13

O14

O15

O16

O17

O18

Y1

Y8

Y13

Y14

Y15

Dark1Dark4

Light1

Light4

Light5

Port1

Port2

Port3

Port4

A13

A16

A19

A20

A21

A22

A23

A24

A25

A26

A27

SC3

SC4

J5

J6

SC1/O7

Y7/SC2

BE12/RE17

BE22/NE10

BE6/Dark3

BE26/BE8

RE15/NE3

P5/O12

Figure 3: Unison Pastels of Munsell Hue YR



2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Munsell

Valu

e

Munsell Chroma

NE9

NE17NE18

YGE1 YGE7

YGE8

YGE10

YGE11

YGE12

YGE13

YGE14

YGE15

YGE17

BGE15

BGE16

BGE17

BE1

BE2

BE25

BE31

BE32

BE33

BE34

BE35

BE36

Y2

Y3

Y4

Y5

Y6

Y9

Y10

Y11

Y12

Y16

Y17

Y18

G18

Grey1

Grey6

Grey13

Grey17

Grey18

Grey19

Grey20

Grey21

Grey22

Grey23

Grey26Grey27

Grey28

Dark5

Dark6

A7

A8

A9

A10

A11

A12

A38

A39

A40

A41

A42

SC18

Light2/Light3

NE15/BE3

BE27/YGE16

Grey25/Grey24

Figure 4: Unison Pastels of Munsell Hue Y


PAUL CENTORE

2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Munsell

Valu

e

Munsell Chroma

YGE2

YGE3

YGE9

YGE18

BGE13

BGE14

G4

G5

G6

G10

G11

G12

G14

G15

G16

G17

G26

G27

G28

G29

G30

G31

G32

G33

G34

G35

G36

Grey3

Grey29

Grey30

A37

A47

SC17

Dark12/Dark11

Figure 5: Unison Pastels of Munsell Hue GY



2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Munsell

Valu

e

Munsell Chroma

YGE5

YGE6

BGE1

BGE7

BGE8

BGE18

G2

G3

G7

G8

G9

G13

G20

G21

G22

G23

G24

G25

BG18

Grey5

Grey12

Grey31

Dark9

Light17Light18

A44

A45

A46

A48

J13

J17

Dark10/G1

YGE4

Figure 6: Unison Pastels of Munsell Hue G


PAUL CENTORE

2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Munsell

Valu

e

Munsell Chroma

BGE2

BGE3

BGE4

BGE5

BGE9

BGE10

BGE11

BGE12

G19

T1

T3

BG17

Grey2

Grey4

Grey32

Dark8

Light15

Light16

A3

SC16

J16

A43/Dark7

Figure 7: Unison Pastels of Munsell Hue BG



2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Munsell

Valu

e

Munsell Chroma

BGE6

T2

T4

T6

BG1

BG4

BG5

BG6

BG7

BG8

BG9

BG11

BG12

BG13

BG14

BG15

BG16

BV13

Grey14

Grey33

Grey34

Grey35

Grey36

Dark15

A2

A51

A52

A53

A54

SC14

SC15

J14

J15

J18

A49/Dark16

BG10/T5

Figure 8: Unison Pastels of Munsell Hue B


PAUL CENTORE

2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Munsell

Valu

e

Munsell Chroma

BG2

BG3

BV4

BV8

BV9

BV10

BV11

BV12

BV14

BV15

BV16

BV17

BV18

Grey8

Grey9

Grey10

Grey11

Grey15

Grey16

Dark13Dark17

Dark18

Light14

A50

A61 A62

SC12

SC13

J9 J10

J11

J12

A1/BV7

Figure 9: Unison Pastels of Munsell Hue PB



2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Munsell

Valu

e

Munsell Chroma

BV1

BV2

BV3

BV5

BV6

Grey7

Dark14

Light13

A4

A30

A31

A32

A33

A34

A35

A57

A59

A60

SC10

SC11

Figure 10: Unison Pastels of Munsell Hue P


PAUL CENTORE

2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18

Munsell

Valu

e

Munsell Chroma

R14

R15

R16

R17

R18

Light10

Light11Light12

Port9

Port10

Port11

A5

A6

A29

A36

A55A56

A58

SC8

SC9

J8

Figure 11: Unison Pastels of Munsell Hue RP



4.2 Hue, Value, and Chroma Distributions

Figures 12 through 14 are histograms of the entire Unison line in terms of hue, value,and chroma. Figure 12 shows that the Unison pastels cover the entire gamut ofhues, though not evenly. There are about twice as many pastels in the hues between5R and 5Y, as there are in the rest of the hues. Human skin tones mainly clusterbetween 5R and 5Y, so this predominance would provide fine colour distinctions forportrait or figure painting.

Figure 13 gives the overall Munsell value distribution of the pastels. The bulkof the pastels fall fairly evenly between values 2.5 and 9.5. There are relatively fewvery dark or very light pastels. Tables 7 and 8 list the five darkest and five lightestpastels. The darkest pastels tend, not surprisingly, towards neutrality, and haveMunsell values near 2. This minimum should be compared with oil or acrylic paints,in which the darkest blacks tend to have values near 1, a full value step darker thanthe darkest Unison pastels. The lightest pastels also tend towards neutrality, andalso do not reach the extremes routinely achieved by oil and acrylic paints. Titaniumwhite, for example, which is the standard artist’s white today, has a value of about9.8, while the lightest Unison pastels only reach 9.4, about half a value step lower.In general, then, Unison pastels have a restricted value range, when compared topaints.

Pastel Munsell Specification Munsell ValueDark 16 8.8B 1.9/1.9 1.9Additional 49 8.6B 1.9/1.9 1.9Dark 18 3.8PB 2.0/4.2 2.0Grey 36 8.5B 2.1/0.3 2.1Grey 13 0.1Y 2.2/0.7 2.2

Table 7: Darkest Unison Pastels

Figure 14 is a histogram of the chromas of Unison pastels. The chromas peakat just over 2, and taper off steadily, reaching a maximum around 16. Very intensecolours, with chromas of 10 or above, attract attention, so most artists tend to usethem sparingly, as accents. The bulk of the colours in a painting are usually of lowor moderate chroma, so the Unison pastel line fits this pattern. Tables 9 and 10list the five least and five most saturated Unison pastels. The pastels in Table 9 allhave chromas of 0.5 or less, so they are very neutral greys. Not surprisingly, theyall belong to the Grey series. The very intense pastels in Table 10 all have similarhues, clustering around reddish orange. Their values are also similar, around 6 or


PAUL CENTORE

Pastel Munsell Specification Munsell ValueLight 1 9.1YR 9.4/0.8 9.4Grey 28 0.4Y 9.4/0.5 9.4Grey 27 4.5Y 9.3/2.5 9.3Light 16 3.9BG 9.2/0.9 9.2Light 3 4.6Y 9.2/4.0 9.2

Table 8: Lightest Unison Pastels

Figure 12: Hue Histogram of Unison Pastels



0

10

20

30

40

50

60

70

80

1 2 3 4 5 6 7 8 9 10

Num

ber

of

Paste

ls

Munsell Value

Figure 13: Value Histogram of Unison Pastels

0

10

20

30

40

50

60

70

80

0 2 4 6 8 10 12 14 16 18 20

Num

ber

of

Paste

ls

Munsell Chroma

Figure 14: Chroma Histogram of Unison Pastels


PAUL CENTORE

Pastel Munsell Specification Munsell ChromaGrey 17 0.7Y 7.8/0.1 0.1Grey 18 4.0Y 8.5/0.1 0.1Grey 36 8.5B 2.1/0.3 0.3Grey 16 2.7PB 6.5/0.4 0.4Grey 28 0.4Y 9.4/0.5 0.5

Table 9: Least Saturated Unison Pastels

Pastel Munsell Specification Munsell ChromaAdditional 13 4.0YR 7.0/15.9 15.9Additional 14 9.5R 5.7/15.7 15.7Orange 7 1.8YR 6.1/15.7 15.7Orange 14 6.9YR 7.4/15.6 15.6Orange 8 3.8YR 6.7/15.6 15.6

Table 10: Most Saturated Unison Pastels

7, so there is not much variety in the highly saturated pastels. 18 of the top 20most saturated pastels, in fact, are in the mid-valued, warm part of the spectrum,clustering near orange. The other two, Blue Violet 12 and Blue Violet 11, havechromas of 14.8 and 13.2 respectively, and have a purplish-blue hue.

4.3 Duplicates

In addition to Munsell characteristics, colour differences between pastels were alsoanalyzed. The CIE DE 2000 difference formula,2,4 commonly abbreviated ∆E00, wasused. This formula depends on an illuminant, so Illuminant C, which is specified inthe Munsell renotation standard, was used in calculations. The lower the ∆E00, themore similar two colours are. When the ∆E00 of two colours is low enough, even if itis not 0, the two colours are indistinguishable. It is not always clear how low ∆E00

should be for indistinguishability, but a cutoff of 2 was used for this analysis. ∆E00

values were calculated for every possible pair of Unison pastels.Table 11 shows all pairs, 18 in total, whose ∆E00 was 2 or less. A painter can

verify for himself that these pairs are duplicates (or nearly so), by applying thetwo pastels in a pair, in thick layers, adjacent to each other. It will usually bedifficult to tell where one colour stops and the other colour starts. From a practicalpoint of view, a painter would not need to purchase one of the pastels in each pair.The manufacturer could similarly replace one of the pastels in each pair with a brand



First Pastel Second Pastel Difference (∆E00)Dark 16 Additional 49 0.2Natural Earth 15 Brown Earth 3 0.3Blue Violet 7 Additional 1 0.5Yellow Green Earth 4 Grey 3 0.8Natural Earth 14 Brown Earth 14 0.9Orange 11 Portrait 4 0.9Orange 11 Portrait 2 1.0Grey 28 Light 1 1.1Light 2 Light 3 1.3Portrait 6 John’s Set 3 1.4Portrait 2 Portrait 4 1.5Natural Earth 18 Brown Earth 1 1.6Natural Earth 18 Brown Earth 13 1.6Orange 16 John’s Set 6 1.6Additional 17 John’s Set 4 1.7Natural Earth 17 Brown Earth 1 1.8Grey 31 Additional 48 1.9Light 2 Additional 7 2.0

Table 11: Duplicate Pairs of Unison Pastels

new colour, thus extending the line’s gamut without increasing the number of pastelsproduced.

5 Other Pastel Brands

The current document has analyzed only one pastel manufacturer, Unison. Compar-ative studies, involving other manufacturers, would be even more helpful to pastelartists. The calculations, including the production of the histograms and plots inthis document, have been largely automated, using code written for Octave or Mat-lab. The measurements are straightforward and reasonably quick, once samples areavailable. A sample in this context is just a piece of paper to which the pastel hasbeen applied, rather than the pastel itself.

The current bottleneck is obtaining samples. While the author owns severalhundred pastels from many brands, he has no complete line from any one brand.Other pastel artists, who do have complete sets, are invited to contribute to further


PAUL CENTORE

pastel analysis by sending the author samples, which he can measure and analyze.The samples should meet the following conditions:

1. The area of each sample should be at least one square inch (or 6 square cen-timeters),

2. The samples should be applied to a standard pastel paper. White CansonMi-Teintes paper is adequate, but sanded papers, such as Wallis or SennelierLaCarte, work well, too,

3. The pastels should be applied thickly enough that the samples are opaque.When in doubt, add more pastel to a sample. Ideally, it should be impossibleto discern the colour of the paper through the pastel sample,

4. The surface of the samples should be reasonably smooth, with no obviousirregularities. Rubbing the pastel with a finger produces a sufficient finish,

5. The samples should be clearly labelled, using the pastel manufacturer’s namingconvention,

6. Do not use any fixative, as this can alter colours. A protective sheet of Glassinecan be used over each sheet of samples, to keep the pastel from rubbing off,and

7. There is no problem using a large number of smaller sheets (say 8.5 by 11inches), for easier shipping.

Once the samples are prepared, they can be mailed to the author, Paul Centore,at 62 Chicago Ave., Groton, Connecticut 06340, USA, who will measure them, andprepare a report, similar to this one, that he will post on his website. Artists shouldbe aware that preparing samples can be considerably more time-consuming and te-dious than it seems, especially since it is important to produce a thick, opaque layer.An entire set of samples can take eight hours or more, depending on the number ofpastels.

Apart from artists, pastel manufacturers are also invited to send samples of theirlines. If the preparation process is too tedious, then the manufacturer can send acomplete set of pastels to the author, who will prepare the samples himself, andgenerate a report. In addition to providing some exposure, the report might also behelpful at identifying unexpected duplicates, or gaps in gamut coverage, that can beused for revision and development of the pastel line.

References

1. Sidney Newhall, Dorothy Nickerson, & Deane B. Judd. “Final Report of the O.S. A. Subcommittee on the Spacing of the Munsell Colors,” JOSA, Vol. 33, Issue



7, 1943, pp. 385-418.

2. CIE. “Colorimetry.” Vienna: CIE Technical Report No. 15:2004, 3rd ed., CentralBureau of the CIE; 2004.

3. Paul Centore, “An Open-Source Inversion Algorithm for the Munsell Renotation,”Color Research & Application, Vol. 37, No. 6, December 2012, pp. 455-464.

4. Gaurav Sharma, Wencheng Wu, & Edul N. Dalal, “The CIEDE2000 Formula:Implementation Notes, Supplementary Test Data, and Mathematical Observa-tions,” COLOR Research and Application, Vol. 30, Number 1, February 2005,pp. 21-30.


colour analysis of unison pastels · the pastels in each series are numbered for individual...

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