HPA 2020 Tech Retreat, Part 5

motion grading

Last time, I talked about the problem of judder—the stuttering or strobing that occurs when there’s fast movement in a scene. The movement may be caused by fast camera movement or by fast movement of objects in a scene—like vehicles. Judder is even more pronounced as we move to more HDR finishing.

At the Hollywood Professional Association’s Tech Retreat in February, Pixelworks discussed their TrueCut motion grading workflow. By analyzing each frame in a shot, the software can smooth out the judder.

The workflow process begins with powerful workstations (either local or cloud-based) analyzing scenes that may need to be adjusted. This isn’t a simple task. Proprietary algorithms perform complex motion analysis. This isn’t a button press and get some coffee. It takes time.

Once the analysis is complete, the TrueCut software integrates with color grading software like DaVinci Resolve or Baselight. Preset options for correct judder are presented for each shot for quick decisions. Or for more creative control, there’s a software control panel (shown at the top of this article).

One way to offset judder is by increasing motion blur.  The control panel allows you to control motion blur via changes to the shutter angle. Yes, changing the perceived shutter angle in post is possible.

Another control is something Pixelworks calls judder angle. This control reduces the appearance of judder, not by motion blur but through pixel interpolation based on the prior analysis of the scene. Between adjusting shutter angle and judder angle, a motion grader can use TrueCut to do a shot-by-shot motion grade for a film.

The demo at HPA showed removing motion blur, adding motion blur, and—more importantly—dialing down the judder. And while almost completely removing judder effects is an option, visually it takes the scene from film to video.

Currently, motion grading occurs during the color grading session. This type of grading, like color grading, really involves creative decisions. I’m told directors/cinematographers have different opinions on the best motion grade for each shot just as they do with color.

As this process is used for more and more films, will we see motion grading move to a new position? Will we see Motion Grader in the credits?

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