CIE Lab, HLC, and Munsell

Introduction

Many paints (and also pencils, pastels, etc.) on this site (20.1% of the total 41743), in addition to the pigment information, also have a color notation. This is a way to describe a color in a standardized way. There are many different color notation systems, I use CIE L*a*b*, Oklab, and Munsell. They help to describe the hue, the lightness, the chromaticity, show the relationship between colors or to find similar ones. Also help in practical tasks like looking for a cooler or warmer or a more chromatic colors.

To learn more those systems, check Handprint or Colour Online by David Briggs.

On this site, I use this data to make navigation easier:

• CIELab and OKLab ab / La / Lb planes for paint brands
• HLC Atlas Navigator
• Predicting mixing path
• Looking for similar paints

Sources

Whenever those notations are available, I display them next to the paint. Sources for color notations (in this order):

1. Published by the manufacturer. For some (mostly Japanese) brands it's common practice to have Munsell values on their color charts.
2. My own measurements. I paint and measure samples (color chips or swatches). Disclaimer: I don't have access to a high-end colorimeter or spectrophotometer, so these numbers are not up to any scientific or industrial standards. I'll give a more detailed description about my method later.

Other Sources

There are some other great sources available for color notations for artist materials:

1. Watercolors: CIE L*a*b* and CIECAM02 values for watercolors are available on handprint.com.
2. Oil: A Munsell explorer is available on colorwell.org.
3. Pastels: Almost 3000 Munsell notations for pastels are available on Paul Centore's An Artist's Guide to Pastel Colours page.
4. Different mediums: Multiple artist brand's CIE readings available in the freiFarbe Colour Database.
5. Different mediums: Color Mixing Tools contains measured data for many paint lines.

Calculations

Depending on the color measurement source, I use the following methods to calculate / interpolate:

• HLC ↔ Lab ↔ XYZ ↔ RGB I use algorithms based on the math from EasyRGB
• Chromatic adaptation algorithms based on matrices from Bruce Lindbloom's page
• XYZ ↔ Display P3 RGB and REC2020 RGB based on the CSS4 working draft algorithms
• When a converted RGB value is out of gamut, currently I simply clamp the value. That's the most rudimentary way to do it, however, in some cases it leads to off result. I'm working on some more sophisticated method.
• Lab ↔ CieCAM02, Munsell ↔ Lab: for conversions/ interpolation I use the colour-science/colour Python package
• For many on the fly calculations, I use Culori.js.
• Displaying the color atlases heavily based on the - still work in progress - CSS4 Color Module. Read more about colors in your browser.

The data sources for the color navigators are:

• HLC Color Atlas by freieFarbe e.V. (Creative Commons license CC-BY-ND 4.0)
• Munsell Renotation Data: Munsell Color Science Lab Educational Resources / RIT

Own measurements

As I mentioned earlier, my own measurements are not up to scientific or industrial standards. For that, I would need to be able to prepare samples in a much more consistent way (e.g. film applicator) and I would need to use a high-end spectrophotometer. But I'm trying to do the best I can with the tools I have in a home/hobby environment.

1. Samples

1. I try to prepare my own samples with a repeatable workflow to get consistent measurements.
   • For watercolor swatches, I paint & measure a concentrated, full-strength sample ("masstone"). For some paints, I also measure a second, slightly diluted sample ("tint"). For samples with an uneven surface, I take an average of three measurements.
   • For gouache and acrylic, I measure a painted tube color sample.
   • For oil, I measure the tube color, painted with palette knife with uniform thickness, and also a second measurement for tints, 1:1 (by volume) mixed with mixing white (PW6/PW5/PW7)
   • For pencils, I draw the samples with simple shading, with tripod grip, medium to high pressure (with the tip of the pencil) and aim for a good even coverage.

   I'll list the papers / boards used later because they can affect the color measurement.

2. I can only make samples of the colors I own, so in some cases I use hand-painted charts from the manufacturers. I only do this if I do not have access to those colors + the entire product line is covered. These hand-painted charts are made with different techniques, which makes it harder to compare brands. But it usually gives a good impression of the product line itself. I add a comment next to the color measurement where the samples came from.

2. Color Measurement

Currently I'm using two different devices:

I found both devices suitable for the current purpose (to make it easier to navigate through paints and show similar colors)

Brands with (manufacturer) Munsell notations

Brands with CIE L*a*b* information