This document provides official CIE recognition of a spectral luminous efficiency function for photopic vision that has been used by vision researchers since the early 1950's. Vision researchers have referred to this function as Judd's modification of CIE V(?). This document proposes to call it the CIE 1988 Modified 2° Spectral Luminous Efficiency Function for Photopic Vision, which has the symbol VM(?). This modification is a supplement to, not a replacement of, the 1924 CIE V(?) function. The difference between these two functions lies only below 460 nm. The 1924 CIE V(?) function is too insensitive with respect to colour normal observers. The 1988 VM(?) would be the preferred function in those conditions where luminance measurements of short wavelengths consistent with colour normal observers is desired.