A linear microchannel plate-reticon array detector is used to characterize phosphor films. These films upconvert vacuum UV radiation into the detector's sensitive spectral range (wavelengths >350 nm). The methodology for measuring the sensitivity as well as the angular dependence of fluorescence of films is described, and absolute as well as relative efficiencies for several phosphors is given. The use of this device circumvents some of the problems inherent in such characterization measurements.