The performance of two nonlinear joint transform correlators?the binary subtracted joint transform correlator and the photorefractive-based subtracted joint transform correlator, has been tested by computer simulations under brightness changes of various target scenes. The input images used in the study were composed of pure- amplitude, pure-phase, and complex data, respectively. Also the performance for input images with complex data transformed by a spatial light modulator that uses the electroabsorption effect of GaAs single crystal has been compared with the mentioned results. The input images with pure-phase and complex data gave better results than those with pure- amplitude data, for various input images with the brighter target scenes. However, the input images with pure-amplitude data were most robust to brightness changes of target scenes.