Like geographic coordinates – longitude, latitude, and altitude – L*a*b* color values give us a way to locate and communicate colors.
What’s the history of L*a*b*?
In the 1940’s, Richard Hunter introduced a tri-stimulus model, Lab, which is scaled to achieve near uniform spacing of perceived color differences. While Hunter’s Lab was adopted as the de facto model for plotting absolute color coordinates and differences between colors, it was never formally accepted as an international standard.
Thirty-one years later, the CIE published an updated version of Hunter’s Lab: CIELab. The correct way to pronounce it is “see-lab”, or “L-star, a-star, b-star,” but some applications and instruments simply call it L, A, B, or Lab.
What does L*a*b* stand for?
Regardless of formalized “color space name” you call it, it’s important to know what L, A, and B stand for.
- L*: Lightness
- A*: Red/Green Value
- B*: Blue/Yellow Value
As an example, see figures 17 and 18, showing the color-plotting diagrams for L*a*b*.
- The a* axis runs from left to right. A color measurement movement in the +a direction depicts a shift toward red.
- Along the b* axis, +b movement represents a shift toward yellow.
- The center L* axis shows L = 0 (black or total absorption) at the bottom.
- At the center of this plane is neutral or gray.
To further demonstrate how L*a*b* values represent specific colors, see flowers A and B, below. We’ve also plotted their values on the CIELAB Color Chart above.
We hope these examples help you better understand L*a*b* color space. If you have more questions about color spaces or methods of color communication, contact our team of experts – we’re happy to help!