This erratum corrects an equation in Appl. Opt. 57, 8751 (2018) [CrossRef] .
© 2019 Optical Society of America
CIE  has recommended a formula for the number of equal perceptible differences (nEPD) of luminance () between a visual-contrast luminance () and its adjacent background luminance (). An incorrect equation, specifically Eq. (4), was given  for the derivative of the recommended formula with respect to , for negative contrasts (). The correct equation is1, 2].
1. CIE, “Grey-scale calculation for self-luminous devices,” CIE 228:2018 (CIE, 2018).
2. R. C. Carter, “Suprathreshold gray scale is implied by thresholds,” Appl. Opt. 57, 8751–8756 (2018). [CrossRef]