Simultaneous measurements of work function (phi) and C 1s core level shift were employed to determine the change in electron affinity (chi) and band bending as a function of hole sheet density on H-terminated diamond for atmospheric and fullerene (C60F48) induced surface conductivity. Contrary to earlier investigations, it is shown that changes in work function do not reflect variations in the position of the surface Fermi level in response to surface transfer doping. Instead, with a transition from -0.96 to -0.33 eV, chi accounts for a significant amount of the change in phi for hole densities between 5×108 and 4×1013 cm-2.