X-Rite ColorChecker Passport, #33-270
The X-Rite ColorChecker® is a unique test pattern scientifically designed to help determine the true color balance or optical density of any color rendition system. It is an industry standard that provides a non-subjective comparison with a “test pattern” of 24 scientifically prepared colored squares. Each color square represents a natural object—human skin, foliage, blue sky, etc, providing a qualitative reference to quantifiable values. Each color will reflect light in the same way in all parts of the visible spectrum, thus maintaining color consistency over different illumination options. Some applications include spectroscopy, machine vision, photography, graphic arts, electronic publishing, and television.
The X-Rite ColorChecker® chart provides an easy way to recognize and evaluate the many factors that can affect color reproduction. To evaluate the effect of varying any given factor, simply compare the chart’s color image to the actual ColorChecker®. It is ideal for testing and standardizing color inspection and analysis systems.
The X-Rite ColorChecker® SG improves on the original 24 patch design by offering a wide array of 140 colors. Specifically designed for digital photography, the X-Rite ColorChecker® SG provides a semi-gloss background with whiter whites, blacker blacks, and more saturated colors. The RezChecker can measure resolution according to the latest international standard (ISO 12233). Gloss gray patch targets have an extended dynamic range (density = 2.4) and can also be used to measure imaging noise. However, specular reflections from the gloss surface may occur for illumination geometries less than 45°/0°. Matte gray patch targets have a small dynamic range (density = 1.6), but are more suited to narrow illumination geometries, such as those used in endoscope imaging.
The color names for each of the squares are given along with the chromaticity coordinates x and y and the luminous reflectance factor Y. Also provided are the Munsell notations and the ISCC/NBS names.
A particularly useful function of the X-Rite ColorChecker® is in determining the L*a*b* values of the test subject. The L*a*b* color model (CIELAB) is the international color measurement standard used to describe all the colors visible to the human eye. It is created to be independent from any device, thus maintaining the consistency in color. The L*a*b* standard consists of "L" (bright/dark axis), "a" (red/green axis), and "b" (yellow/blue axis) components. A positive value of a* describes the redness of the color, a negative a* the greenness. Similarly, a positive b* denotes yellow, and a negative b* denotes blue.