Although the file is encoded as a grayscale image, the embedded gray gamma 2.2 profile helps to ensure that the L* values will remain intact when translations of the target to an RGB or CMYK color space occur. The 30 patches are deliberately arranged as a gradient step wedge that spans the full L* value range from 0 to 100. The 30 patches are also laid out in a linear arrangement as well for better space utilization on some of the AaI&A test equipment, but the measured patch data are electronically reassembled into their correct rectangular image geometry when the I* metric evaluation is conducted. Like the standard AaI&A 30 patch color target, the new B&W target has 30 patches to give it compatibility with AaI&A standard light fade testing procedures.
The design of the new grayscale test image is fairly straightforward. An I* metric evaluation will therefore score both tone and color accuracy even for a “black and white” printing process. If the print does exhibit a certain hue, for example, a sepia toned print, or a narrow range of hues (e.g., a split tone process), then the hue and chroma values in the print define a very narrow range of color but color nonetheless. It’s just that all colors in the print have very little or no chroma, and when chroma goes to zero hue becomes undefined. A black and white print still possesses color values.
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