- 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.
Currently I'm using two different devices:
- NCS Colourpin Pro It comes with a ceramic calibration tile, has reasonable repeatability.
- Nix Spectro 2 It also provides reflectance data.
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.
For swatches uploaded after 2022.12.01 I use the following setup:
- I scan the images with an Epson V600 scanner in Silverfast SE Studio 9, the only software I've found which can save files in ProPhoto RGB color space (Epson's own MacOS software - Epson Scan 2 - can only create 8-bit files in Adobe RGB color space at best).
- For slicing the images I use Adobe Lightroom Classic / Photoshop, and keep the color space as ProPhoto RGB throughout the process.
- I export the images to sRGB JPEGs and Display P3 PNGs. Depending on your monitor, operating system, and your browser, you may get different images.
The sRGB (standard RGB) color space was created back in 1996, and it's still the default color space for the web. Although most of the modern monitors and mobile displays are capable of displaying wider gamut than the sRGB can offer, web developers are still using the sRGB color space to define colors.
When processing swatches, I export images to sRGB JPEGs and Display P3 PNGs. Depending on your monitor, operating system, and your browser, you see the best possible format.
Here are two examples: The same scans, exported to sRGB color space and Display P3 color space (on the right). The only difference is the color space, the images are the same, no other modification.
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
There are some other great sources available for color notations for artist materials:
- Watercolors: CIE L*a*b* and CIECAM02 values for watercolors are available on handprint.com.
- Oil: A Munsell explorer is available on colorwell.org.
- Pastels: Almost 3000 Munsell notations for pastels are available on Paul Centore's An Artist's Guide to Pastel Colours page.
- Different mediums: Multiple artist brand's CIE readings available on freiFarbe under `Open Colour Systems Collection (OCSC) 2.0`.
- Different mediums: Color Mixing Tools contains measured data for many paint lines.
For some (mostly Japanese) brands it's common practice to have Munsell values on their color charts.