Noel, the chart is useful for something else. It's great for demonstrating how Photoshop can ruin the tones of an image when downscaling. When resizing/transforming, Ps neglects to temporarily convert values to linear space for operations that involve interpolation. A workaround to achieve correct interpolation is to convert the document to a linear profile in 16-bit mode, do the operation that involves resampling, then convert the document back to its gamma-corrected profile. (Note that Ps does not do bicubic resampling in 32-bit mode. There is an option of "Bicubic Automatic" in 32-bit mode in CS6, but it results in bilinear. I wouldn't want the agressive over-sharpening produced by "Bicubic Automatic" when down-scaling, anyway.) An example of bicubic resizing to 50 % width and height follows. Here is the image mangled by Photoshop's usual resizing by interpolating gamma-corrected values: Here is the good result of resizing by interpolating temporarily linearized values:
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