Chroma Complications

Opposite, you see one attempt at showing colorfulness, or chroma, and hue. For a specific lightness value, all of the colors in sRGB (what most computers can display) are displayed. There's a couple things to note:

  • Note how, as you move the lightness up past 0.8, the range of colors becomes more and more tilted towards green. As you decrease lightness, especially past 0.3, note how blue and purple dominate. There's no such thing as dark saturated yellow or bright saturated purple.
  • In general, as you move towards white and black your options diminish. This is sometimes disambiguated as chroma vs. saturation, although these terms are often not used precisely. The distance from the origin here is chroma, whereas saturation is measuring in comparison to a gray of the same lightness. Saturation can be thought of as chroma divided by lightness.
  • Try to imagine this as a 3D shape: each individual image you see is a cross-section. The resultant shape is not a cylinder or any clean geometry, but instead a rather irregular polygon whose shape is determined by the idiosyncrasies of the human visual system. Any system that tries to represent color using lightness, colorfulness, and hue will have to choose between consistent coordinate bounds and consistent interpretation of colorfulness and lightness.
  • Set the lightness to around 0.5. Note how the blue wedge is clearly broken up into chunks, but the green wedge looks much more continuous. (This is a pretty subtle effect, so don't worry if it's not obvious.) In general, we're quite sensitive to blue, and not so much to green—you may have noticed this if you watch compressed videos where cool-colored shadows look blocky or glitchy. This happens because the video format simply runs out of colors to create a smooth gradient. Green doesn't have this problem, because two colors in sRGB that are off by a little bit won't look that different to our eyes.

Chroma Complications

Opposite, you see one attempt at showing colorfulness, or chroma, and hue. For a specific lightness value, all of the colors in sRGB (what most computers can display) are displayed. There's a couple things to note:

  • Note how, as you move the lightness up past 0.8, the range of colors becomes more and more tilted towards green. As you decrease lightness, especially past 0.3, note how blue and purple dominate. There's no such thing as dark saturated yellow or bright saturated purple.
  • In general, as you move towards white and black your options diminish. This is sometimes disambiguated as chroma vs. saturation, although these terms are often not used precisely. The distance from the origin here is chroma, whereas saturation is measuring in comparison to a gray of the same lightness. Saturation can be thought of as chroma divided by lightness.
  • Try to imagine this as a 3D shape: each individual image you see is a cross-section. The resultant shape is not a cylinder or any clean geometry, but instead a rather irregular polygon whose shape is determined by the idiosyncrasies of the human visual system. Any system that tries to represent color using lightness, colorfulness, and hue will have to choose between consistent coordinate bounds and consistent interpretation of colorfulness and lightness.
  • Set the lightness to around 0.5. Note how the blue wedge is clearly broken up into chunks, but the green wedge looks much more continuous. (This is a pretty subtle effect, so don't worry if it's not obvious.) In general, we're quite sensitive to blue, and not so much to green—you may have noticed this if you watch compressed videos where cool-colored shadows look blocky or glitchy. This happens because the video format simply runs out of colors to create a smooth gradient. Green doesn't have this problem, because two colors in sRGB that are off by a little bit won't look that different to our eyes.