Zero is the lowest value possible and represents ideal black. They vary by steps that are intended to be visually equal when viewed under the intended illuminant, daylight. Since human visual response is non-linear, visually equal gradations of lightness are not equal steps of reflectance. Approximate daylight reflectances for the various Munsell values are given in following table . The spectral colors have the maximum chroma, or are 100 percent pure.
Chroma is on the horizontal axis of the constant hue segment .
Thus minimally saturated colors have a chroma designation of two, while the strongest colored specimens producible will be 18 or 20, depending on the hue. Again, the steps are intended to be visually equal. The locus of colors producible by mixtures of black, white, and pigment would be curved lines, such as the dotted line of shown . The system is built up at each hue by adding progressive columns of colors to the nine neutrals of the same value. Each column of colors departs from the equivalent neutral by two additional steps of chroma.