Enhancing time-altered motion by blending frames

When you time-stretch footage to a slower frame rate or to a rate lower than that of its composition, movement can appear jerky. This jerky appearance results because the layer now has fewer frames per second than the composition. By default, After Effects fills in the missing frames in slow-motion footage by repeating the last frame shown. After Effects can create a more gradual transition between frames by interpolating new frames between existing ones.

When you time-stretch or time-remap footage to a frame rate that is faster than the original or higher than that of its composition, After Effects skips many of the original frames to achieve the new rate and, consequently, movement can appear jerky. Frame blending combines the remaining original frames to create smoother fast motion. (See Time-stretching a layer and About time-remapping.)