Mt. Baker Research L.L.C.
2921 Sylvan Street/P.O. Box 28370
Bellingham, Washington 98228-0370

Defining Color Standards

Phone: (360) 650-0771 E-mail: <jackroot@mtbakerresearch.com>

Mt. Baker Research L.L.C. Tutorial

Color Gamut

Our ceramic color standards are used for instrument testing, calibration and color management. They offer the widest color gamut available in the international marketplace.

CIELAB b* vs. a* gamut plot. Conditions: D65 Standard Illuminant. 2° Standard Observer. (8°/t) hemispherical specular-included geometry. Key to symbols: ◆, 36 chromatic color standards (Mt. Baker Research). ◆, 8 BCRA Series II tiles (Ceram Technology Ltd.). ━ & ━, chroma boundaries.

The 1st chart shows the color distribution of our original color sets in comparison with the chromatic Ceram Series II tiles. The closed solid lines represent the chroma contours for our chromatic color standards vs. the Ceram tiles. The CIELAB chroma, C*, corresponds to the scalar distance from the origin of the b* vs. a* chart to any data point.

The area enclosed within a chroma contour provides a convenient measure of the gamut of colors. The 8 Ceram Series II chromatic tiles define the color gamut enclosed by the blue solid line.

The color gamut for our original color standards (enclosed by the red line) is defined by the 14 chromatic standards that exhibit the largest CIELAB chroma values. The other chromatic color standards in our original sets are distributed within the red chroma boundary. Many of these color standards extend the available gamut of colors, and all of them span the gamut very well. (Note: Although the data are not shown here, several of the color standards included in the Diagnostic Tile Sets significantly extend the color gamut.)

The next chart shows a measure of the gamut of colors that includes the CIELAB lightness parameter, L*. Over the full range of L* our original chromatic color standards increase the chroma and the available gamut of colors. This more complete coverage of color space will improve results for instrument testing, characterization, and color management.

CIELAB C* vs. L* gamut plot. The chroma, C*, is given by [a*² + b*²]^0.5. Conditions & Key to symbols: see preceding chart.

The next chart shows the characteristics of our achromatic color standards vs. the achromatic Ceram Series II tiles and the X-Rite ColorChecker Chart.

CIELAB L* vs. median reflectance factor (360 - 780 nm). Conditions: D65 Standard Illuminant. 2° Standard Observer. (8°/d) hemispherical specular-included geometry. Key to symbols: ◆, 13 achromatic standards (Mt. Baker Research). ◆, 11 CERAM achromatic tiles (Ceram Technology Ltd.). ◆, 6 neutral patches from the GretagMacbeth ColorChecker Chart (X-Rite, Inc.).

The error bars shown on this chart correspond to the CIELAB chroma, C*, values, which measure the deviation from neutrality. Our achromatic color standards span the full range of L* with roughly comparable neutrality to the Ceram tiles. (Note: For a perfectly neutral standard the value of C* is zero.)

Dr. Noboru Ohta reported the data shown here for the ColorChecker Chart. You may download Dr. Ohta's data from the resources page at the web site of the Munsell Color Science Laboratory. (Notes: The measurement geometry is not listed. The original reference is N. Ohta, The Basis of Color Reproduction Engineering (Japanese), published by Corona-sha Co. of Japan in 1997.)

The final charts in this series extend the 1st 2 (see above) by adding data for 44 chromatic color standards that are not included in the original color sets.

CIELAB b* vs. a* gamut plot. Conditions: D65 Standard Illuminant. 2° Standard Observer. (8°/d) hemispherical specular-included geometry. Key to symbols: ◆, 80 chromatic standards (Mt. Baker Research). ◆, 8 BCRA Series II tiles (Ceram Technology Ltd.). ━ & ━, chroma boundaries.

As before, the gamut for our color standards (enclosed by the red line) is defined by the 14 standards that exhibit the largest CIELAB chroma values. The other chromatic color standards are distributed within the red chroma boundary. Many of them extend the available gamut of colors (see below), and all of them span the gamut very well.

CIELAB C* vs. L* gamut plot. The chroma, C*, is given by [a*² + b*²]^0.5. Conditions & Key to symbols: see preceding chart.

Over the full range of L* our chromatic color standards greatly increase the chroma and the available gamut of colors. This more complete coverage of color space will improve results for instrument testing, characterization, and profiling.

Linked Resources

• The websites published by ColorTec and Norman Koren feature introductory tutorials about light science, color vision and color management.
• Visit WebExhibits for a tutorial about color vision and visual perception.
• For an overview of the CIE colorimetry system read Dr. Yoshi Ohno's technical article CIE Fundamentals for Color Measurements.