Shake It Up

A Tutorial of the Trailing Effect filter in Video Action

By Paul M. Grossman

Today we have a quick visual effect. I first recall seeing this effect in the psychological thriller Jacob’s Ladder and later in The Mask It looks like a person is shaking or moving at an extremely high rate of speed. It was used on television in CBS’s series The Flash and more recently on Fox’s X-Files to portray a villainous bug-like entity. Try to keep your head as we use two filters to generate this effect.

The Video shoot is about 8 times as long as the effect. The camera is steadied on a tripod and the talent moves about the scene. In this case I sat in a chair and wiggled my head about for 40 seconds. The final result is about 5 seconds long. Shoot a few minutes of footage with a person moving from place to place within the scene and you are close to the manic speeds of Jim Carrey’s alter ego in The Mask.

SpeedChange

Place the clip on track 3. The next step is to speed up the clip. Right click on the clip and select Speed Change. Change the setting to 800%.

Copy Clip

Next copy the clip and place the copy on a track below the original so that it lines up exactly. This is the clip that that will have two effects applied to it. One filter effect is the Trailing Filter, however the filter only works with an alpha channel transparency. We will use the second copy of the clip and the Transparency Filter to generate the alpha channel transparency on the fly.

Uniform Transparency

All that needs to be done to the Transparency filter is to change the Foreground Transparency to about 90%. Because we are overlapping the same clip on itself the Transparency filter will not show any effect in the Preview Window.

Trails

Next apply a trailing effect to the clip. This effect is not found in the Apply Effects dialog. Instead it is found under the Tools menu. Select the Wind or Defocus setting and set the decay setting to 1% for maximum trails. Setting the filter to 0% decay is worse than 1%. Because the trails never clean up and the video will darken during the render.

That’s all there is to it. Please note that although the effect is quick to generate, use it sparingly. The combination of these filters do take more time than normal to render.

Click here to see an mpeg clip of the effect
Click image to see an mpeg clip of the effect

About DPS Video Action

Video Action for Windows NT is the professional’s choice for broadcast quality digital video editing. Together with DPS’ award winning hardware Video Action delivers a full featured editing solution. The software package comes bundled with all of DPS’ desktop products – DPS EditBay, DPS SparkPlus, DPS Perception, and DPS’ real-time editing solutions the DPS Perception RT and DPS Perception RT3DX. The power of this software is apparent when it is combined with DPS’ award winning hardware. DPS Video Action software makes it easy to move from one DPS hardware platform to another without the need to learn a new editing program or user interface.

About DPS

About DPS – DPS is a leading designer and manufacturer of electronic hardware and related software used for recording, editing and processing broadcast quality video and audio material. The company has three business segments: Broadcast, Professional Post-Production, and Security. DPS products are used throughout the world by television broadcasters, video production studios, post-production facilities and by the computer-based desktop video production industry. Visit our web site at www.dps.com.