Motion Blur with Shutter Angle and Phase Settings
Motion Blur with Shutter Angle and Phase Settings

from's ''25 Cool Things about After Effects 5.5'' Series

Using Motion Blur and Shutter Angle Settings
Bill O'Neil Bill O'Neil
Chicago, Illinois, USA

©2002 by Bill O'Neil and All rights are reserved.

Article Focus:
Bill O'Neil demonstrates the use of After Effects 5.5's Motion Blur with shutter angle and phase settings to create a 'smear' of color that will become one of the most useful clips in your digital spice rack.

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Shutter Angle:
For this tutorial, you'll need the two paintings you created with Vector Paint in part one. We will fly these across the screen with the shutter wide open and motion blur turned on to create our Light Storm. The shutter angle setting is the most important step in the process of creating the Light Storm effect. First I will discuss the nature of the shutter angle. Get your textbooks out.

When a motion picture camera is running, a half disc (180 degrees) spins in front of the gate allowing light to pass through for the length of a frame. When the gate is covered by the disc, a claw grabs the film sprockets and yanks it into place for the next exposure.

Many film cameras allow for a variable shutter. That is, the angle of the spinning disc can be changed to allow for a longer or shorter exposure during the length of a frame (usually 1/24 of a second). Ridley Scott employed this technique in some of the fight sequences in “Gladiator”. He narrowed the shutter to around 20 degrees which captured a shorter “instant” of the scene. This created a more “solid” frame that has minimal motion blur.

After Effects allows us to do the opposite. We can open up the shutter all the way (360 degrees) which captures the maximum amount of motion in the scene per frame exposure. This will maximize the length of the smear when we move our paintings through the frame. You’ll find shutter angle in the comp’s advanced settings. Go ahead and set it to 360 degrees and turn on motion blur.

Let's Get Started:
Create a new 2 second comp in your preferred size. I use NTSC D1, 720 x 486. Download the project file (if you haven't already). In it you'll find the two “whoosh” files. Import the footage into your project and drag your two still paintings into the comp. Now comes the fun part.

Drag “Whoosh 1” just out of the left side of frame and set a key frame. Go up to the 20 frame mark and drag the painting all the way to the right just out of frame. Now scale down the height values at the beginning and end of the shot with a key frame in the middle set at its full height. This allows the whoosh to enter and exit frame as a sliver while expanding in the middle.

Do the same with “Whoosh 2”. Now copy the clips and alternate them across the two second timeline so they overlap. Start some at different entry and exit heights to change it up a bit. Preview the shot and adjust to taste.

Click here to see larger picture.

Don't forget to turn on the Motion Blur.

There are no rules here. Make some of the clips longer than twenty frames to vary the speed of the light storm. Note how the splotches of color react differently to the blur. You may even want to go back and write over your painting with bigger or smaller splotches until you reach the desired effect. Actually you can drag just about anything across screen: stock explosions, vector shapes, pictures of your kids. The results will always be interesting with the shutter wide open.

I used “add” in transfer modes to really beef up the light values when they pass over each other.

Next, we will super-charge this raw light storm with some additional filters. First, pre-compose the layers (create a new comp of the same length and drop in the light storm comp.)

The Glow filter will soften and bloom out the brightest areas of the storm. First we will adjust the hue, saturation, and lightness values (Effect, Adjust, Hue/Saturation).

I dialed the Master hue to +177 to shift the colors into a cooler range. I also removed some of the color by bringing the saturation level down to -60. I brought the lightness down to -9.

Now add Glow to the mix (Effect, Stylize, Glow). I brought the threshold down to around 68% and increased the radius to 52 to spread out the edges of the bright areas. I also brought the intensity down to .6 to settle down the highlights. Under the Glow Operation setting, I used Color Dodge which gave the storm more contrast.

Because each painting is unique, be sure to adjust both the Hue/Saturation and Glow settings until you have the perfect looking light storm.

Trapcode’s Shine plugin will also do wonderful things to the light storm. Be sure to keep the ray length down to around 2 so it doesn’t bleed off the edges of frame.

When you are satisfied with motion and glow settings of your light storm, render it out with its alpha. In part 3 we will bring our Light Storm to life by bending it around objects in the scene using Bezier Warp.

Did you miss one of the sections? View:

Part One: Using Vector Paint to create a color wall of splotches

Part Three: Bending Light and Other things with Bezier Warp

Bill O’Neil

Would you like to see some examples of how I used this technique? Click here

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