Lab Color

Lab color, also called CIELAB, describes a color by how people see it rather than by how a screen or a press makes it. It uses three values, L* for lightness, a* for green to red, and b* for blue to yellow, and the International Commission on Illumination (CIE) defined it in 1976.

Because Lab doesn’t belong to any one device, it serves as a common reference. Color management converts between RGB and CMYK through it, and print shops measure printed colors in Lab to check them against a target. CE.SDK designs use sRGB, CMYK, and spot colors, and its CMYK conversions run on ICC profiles, which pass colors through Lab or a related CIE space.

RGB and CMYK values are instructions for a particular device. The same RGB numbers look different on two monitors, and the same CMYK numbers print differently on two presses or papers. Lab instead describes the color itself, as seen by the CIE’s standard observer, an average of how people match colors in controlled tests. So one set of Lab values means one color, whatever will display or print it.

Lab is also built so that equal distances roughly match equal visual differences. The match isn’t perfect, especially for saturated colors, which is why newer formulas adjust for it.

CE.SDK’s design colors are sRGB, CMYK, and spot colors, and Lab works inside the ICC profiles that convert between them. Each document can use the profile its printer supplies, with a bundled US press profile as the default.

The rendering intent decides how colors outside the printable range land. CE.SDK offers the four ICC intents, perceptual, relative colorimetric, saturation, and absolute colorimetric, with relative colorimetric and black point compensation as the defaults.

IMG.LY’s AI benchmarks use CIEDE2000, the current Delta E formula, to measure how far AI-generated images drift from a brand’s required colors.