This page is inspired by the Munsell book of color. It aims at showing the sRGB gamut volume (all the visible colors that can be encoded as sRGB triplets), projected into a perceptually uniform lightness/chroma space (using JzAzBz color space), and sliced across hue planes. The sRGB space is the lowest common denominator of all general-audience screens, and is deemed fit to choose colors for GUI, logos and drawings that should sit correctly on any display. The color patches are sampled with perceptually even steps, on both lightness and chroma axes, meaning that the delta E should be uniform between two neighbours patches, wherever they sit in the graphs.
The following charts can be used for :
- training your eyes to color theory and color differences,
- diagnosing gamut escapes in sRGB space (if you see some constant-hue colorful gradient having an unexpected hue shift at its lowest or highest end, you can check here if there is a way to encode the desired hue at the requested lightness),
- choosing color harmonies that are perceptually even and symmetrical (you may need to use your OS color picker on the charts).
All graphs have chroma on the horizontal axis and lightness on the vertical axis. The vertical line of chroma = 0 goes through the central grey gradient. Chroma is expressed as the radial distance between each patch and the central grey axis. All hue angles are given in JzCzHz, derivated from JzAzBz space by re-writting the opponent orthogonal color dimensions into polar dimensions.
All graphs also have a toolbar of buttons, on the bottom, that allow to change the background shade to compare the color appearance in different surrounds. This will illustrate the Hunt, Stevens and Bartleson-Breneman effects.
For an explanation of the dimensions of color and the meaning of chroma vs. lightness, I have put a whole page about that in the darktable documentation.
Graphs are drawn with the excellent Colour Python library.
The following 3 graphs are adjusted in hue to display the sRGB primary colors.
The following are the same graphs, but drawn in a continuous setting :
#Hue marching over lightness-chroma planes
The next section shows 24 hue slices uniformly sampled every 7.5 °.
#Lightness marching over chroma-hue planes
The following graphs browse the gamut in the orthogonal direction compared to the previous sections. We put hue angle over the horizontal axis and chroma over the vertical axis.
SAFDAR, Muhammad, CUI, Guihua, KIM, Youn Jin, et al. Perceptually uniform color space for image signals including high dynamic range and wide gamut. Optics express, 2017, vol. 25, no 13, p. 15131-15151. https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-25-13-15131&id=368272 ↵