CIELAB Color Space Explained

While it’s miraculous that the human eye can see millions of colors, our ability to distinguish color variations is not quite as keen. That’s because multiple factors influence human color perception including lighting, the angle from which we view an object, a person’s age, the effect of background, and more. This inability to accurately identify exact color matches can become problematic for designers or manufacturers when attempting to duplicate color standards and determine color differences.

A more precise means of color matching is needed to achieve a true quality control program.

In the 1970s, the International Commission on Illumination (CIE) recognized the limitations of tristimulus color spaces like Yxy to express color. Equal distances in the x,y chromaticity diagram did not correspond to equal perceived color differences and a more accurate way to measure color was needed.

Fortunately, there is CIELAB

CIE created the L*a*b* color model for standardizing and simplifying color communication no matter what device one uses to measure it. CIELAB is a more uniform space where the distance between the points agrees better with visual appraisals.

What Is CIELAB Color Space Used For?

CIELAB encompasses the range of human color perception. Through color measurements, CIELAB color space distinguishes color differences with precise accuracy using three color values.

This accuracy enables the reproduction of an exact color on a consistent basis. The L*a*b* color measurement is critical for manufacturers and designers who need to regularly replicate the same product/brand colors to meet standards.

How Does CIELAB Work?

Using a spectrophotometer, a user measures an object or sample. A light within the spectrophotometer is shown onto a sphere which illuminates the sample at a specific angle for optimal viewing and color measurement.

The output from the spectrophotometer is the sample’s reflectance (%R), which in the amount of light reflected at each wavelength of the visible spectrum (normally 400 nanometers (nm) to 700 nm.) The %R data is converted into a set of tristimulus values that take the light source and the specific standard observer function into consideration. The tristimulus values are then converted to a set of light-specific L*a*b* value.

The L*a*b* values are calculated from the tristimulus values (X,Y,Z). The location of a color is defined by its location in a three dimensional, rectangular coordinate system where:

• L* measures whether the sample is light (high L*) or dark (low L*)
• a* and b* represent the chromaticity (hue and chroma) of the sample
  • -a* indicates colors in the green direction
  • +a* indicates colors in the red direction
  • -b* indicates colors in the blue direction
  • +b indicates colors in the yellow direction

Using the values on the L*a*b* coordinate system, one can calculate the differences between colors which allows for more precise color quality control and color difference appraisals.

Ensuring Color Accuracy with CIELAB Color Space

If accurate color measurement and color management is critical to your success, Datacolor has a wide range of color management instruments from which to choose. From handheld color readers to bench top spectrophotometers, our color management instruments ensure accuracy when using CIELAB color space, or your preferred color space or model. Connect with us today to learn more about our many color management options.