The problem for proper rendering of spatial frequencies in digital imaging applications is to establish the relative contrast sensitivity of observers at suprathreshold contrast levels in typical viewing environments. In an experimental study two methods of evaluating spatial contrast sensitivity were investigated, using targets of graded tonal modulation, at which observers were asked to point to the perceived threshold locations. The results produced by these two methods were rather different from those of the classical methods of vision science, showing a much lower sensitivity over a broader range of spatial frequencies. These may be regarded as complementary to CSF data derived from single- frequency Gabor stimuli and prove to be better suited to the needs of practical imaging applications.