Analysis of User Preferences for Film Grain Noise in Images and Video Sequences

Film grain is an artifact of analog photography caused by the silver halide process that, for a variety of reasons, movie directors and photographers want to preserve in the digital age. We conducted an empirical study to determine user preferences for the amount and type of noise added to still images and video. We selected a diverse set of images and video sequences covering a variety of subjects and signal properties. We then added different amounts of film grain noise and white Gaussian noise. Pairwise comparisons of still images show that users prefer film grain over Gaussian noise only at one intermediate level of noise; at low-level noise, the preference of film grain over white Gaussian noise is not statistically significant; there is no clear preference at the highest level of noise. Pairwise comparisons between different levels of film grain and white Gaussian noise show a clear (statistically significant) preference for the lower amount of noise in all cases. For video sequences, we compared two levels of film grain noise to noise-free sequences. The results indicate that users prefer noise-free video over both levels of film grain noise, and lower over higher level of film grain noise.