Spot Color Tone Value is a method to quantify the tonality of spot inks. Like EDA, it has values of 0% for paper, and 100% for solid (100%) ink.
Unlike EDA, SCTV is computed from CIELAB color values. It computation is designed to give equal SCTV value increases for visually similar color changes in a tint ramp, across a wide variety of spot ink colors. For this reason, calibrating the SCTV response of a spot ink to a linear target produces a tint ramp whose steps are visually uniform.