Effects of motion picture frame rate on material and texture appearance

Abstract

High frame rate film should decrease motion blur and temporal aliasing allowing viewers to see more detail. Here we assessed how frame rate affected perception of detail in fabrics and costume ornamentation in three experiments. Live action footage with a fashion show theme was captured at all combinations of two resolutions (2k and 4k), three frame rates (24, 48 and 60 fps), and two shutter angles (180° and 358°). In the first experiment, participants rated the sharpness of a clip of a moving garment relative to a stationary clip. In the second experiment, participants rated (1) image sharpness and (2) quality of motion of 20-s sequences of costumed actors walking on a catwalk. In the last experiment, observers viewed pairs of image sequences and made direct pairwise comparisons while attending to the quality of motion, realism and detail in the garments. As expected, fabric detail became noticeably less distinct when in motion. Motion quality and image sharpness ratings improved with increasing frame rate, especially from 24 to 48 fps. Sharpness ratings were higher for 180° than for 358° shutter angle but the effect was small except at the lowest frame rate. Given the relatively weak effects of shutter angle, we conclude that aliasing and judder were stronger determinants of perceived detail than motion blur. Our results show that naive observers perceive enhanced detail in HFR film sequences of moving fabrics. We argue that this improved perception of detail could underlie both the positive and negative reactions to HFR film, depending on the nature of the content and whether it lends itself to such high fidelity.