Motion

Real motion blur, not fog

Blur follows speed and vanishes at rest; a constant haze is not motion blur.

Top: a yellow circle slides in with a blue streak behind it that shortens to nothing as it stops. Bottom: a still circle with faint ghost copies, crossed out.streak follows speed, gone at rest ghosts and fog on a still object start near a half-frame exposure

Takeaways

  • Blur depends on speed, shutter and phase.
  • A stationary object is never smeared.
  • Test around a half-frame exposure.
  • More samples when ghosts show.
  • Defocus, glow and glass are different effects.

What it means

Real motion blur comes from a shutter open for part of each frame: a fast object smears along its path, and a still object is sharp. A constant spatial blur, or ghost copies that never merge, looks like fog. Start from a half-frame exposure (a 180 degree shutter, 1/48 s at 24 fps) and add samples until the ghosts disappear.

In a RasanAI film

Fast moves are rendered from time samples, with the shutter and sample count logged, rather than faked with a CSS blur. Edges are checked for repeated silhouettes. Blur is kept off information the viewer needs to read, and large post-blur is avoided where hidden pixels are missing. Staccato graphic motion may stay sharp on purpose.

Origins and sources

Adobe's documentation on temporal blur, shutter angle and sampling. The 180 degree figure is a conventional starting point, not a rule.

Evidence: Studio practice (software vendor documentation).

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