In the study of perception, just noticeable differences measure the very limits of human abilities to detect the faintest of differences between, say two adjacent colors almost exactly alike in a continuous spectrum of 100,000 colors. Ad Reinhardt’s paintings rely on these vaporous distinctions, with some gradations revealing themselves only after many minutes of focused viewing. This is fine for art but not for data. Rather than operating at such an exquisite threshold of perceptual acuity, data displays must be clear, assured, reliable, sturdy. In designing information, then, the idea is to us just notable differences, visual elements that make a clear difference by no more – contrasts that are definite, effective, and minimal.