Abstract Relative light conversion factors ? and ?total were experimentally determined for various LiF detectors after irradiation with protons and deuterons. The experimental results are used for finding the function ? (Ei) in a wide energy range. This function is quite different for peaks 5 and 7 of all LiF materials investigated. The relative light conversion factor of peak 7 is clearly greater than unity which is of practical importance in neutron dosimetry.