Measurements carried out on semitransparent S1 photocathodes which indicate that their surface resistivities depend critically on the processing techniques used are described. The results show that, in general, S1 photocathodes having good long wavelength response (≳1 &mgr;m) exhibit high surface resistivities ∼M&OHgr;/&laplac;. A method is also outlined by which improved near infrared (NIR) photoresponse can be obtained for an Ag‐O‐Cs photocathode, and a physical interpretation is suggested to explain the observed characteristics.