Ink Concentration

On press the ink film gets thinner and thicker, the ink gets stronger or weaker in the fountain, and the colour walks. The Concentration picture shows that walk: the ink at 50 to 150 % of its measured strength, in 10 % steps, computed from the spectra.

How it is computed

For a transparent ink on a substrate the reflectance at a concentration c follows from the two spectra the drawdown already has:

Each rung is then integrated under the chosen illuminant and observer like any other sample. The 100 % rung reproduces the library's published Lab to the second decimal, which is the check that the spectral pipeline is right. Change the paper and the whole ladder moves with it.

Reading the ladder

The weaker rungs sit above the large 100 % patch, the stronger below. Lightness moves most, chroma follows, hue barely; a 10 % strength step is usually 1–2 ΔE₀₀ on a mid-tone. Click a rung to see it beside the aim and read its distance and hue shift.