Spectrophotometers measure the visible spectrum

• CIELab – Observer/Light Source/Object
• Color space is defined by the CIE, based on one channel for Luminance (lightness) (L) and two-color channels (a and b).
• Delta E – Metric defining single color difference: Spot Color
• ΔE - (Delta E, dE)
• Delta E 2000 current standard
• E-Factor – Metric Page/Image difference: Process Color
• Cumulative Relative Frequency(CRF) of the 95th percentile
• Quality of a color match