FEBRUARY 12, 2003
Time Remapping
Turn Turn Turn
by Stephen Schleicher

There have been a lot of commercials playing lately that feature the product spinning around in a circle and randomly speeding up and slowing down. This is not some fancy variable speed turn table, but rather something that can be done easily inside Adobe After Effects with the Time Remapping feature.

Time Remapping allows you to expand, compress, freeze, or even play footage backwards. In the case the recent slew of car commercials, speeding up and slowing down the footage is a snap.[an error occurred while processing this directive]For this example, I shot a bust of Batman spinning at a constant speed. To make sure there was enough footage for the 5 second final effect, I shot over 30 seconds of footage. The footage was digitized in Final Cut Pro and imported into After Effects.

Start out by shooting way more footage than you intend to use. This will ensure you have plenty of footage in case you need to speed up considerably (like 800% or more).

Here are the steps involved in Time Remapping the footage.

Create a new composition with a duration of 5 seconds.

Place the footage in the Timeline. You may need to slide the clip into a more appropriate starting position.

With the video layer selected, go to Layer>Enable Time Remapping or press Command+Option+T on the Mac or Control+Alt+T on the PC. At first you may not see any difference in the Timeline or on the clip, but if you press the R key twice quickly (RR), you can bring up Time Remap property for the layer.

Twirling down the Time Remap arrow will reveal a graph that describes the speed or motion of the clip. Two keyframes are automatically created, one at the beginning with an initial speed of 0% and the ending keyframe with a value of 100%. All of the frames in between run at a constant rate so the graph looks like a steady incline. Time Remapping works by altering this graph so that time is displayed differently.

There are several different ways to alter this graph and thus the speed of the clip. Most users will add keyframes to Time Remapping graph and adjust the bezier curves to match their needs.

I like to alter the graph a different way.

Double click the video clip in the Timeline to open the clip layer window. You will notice the usual time controls in the window, but instead of one time control, there are two. The lower control is the normal Time Control, while the upper Time Control alters the Time Remapping value graph.

The lower time control marker controls the the layer as normal, the upper control marker determines how much time-remapping will be done.

To add new keyframes and alter the speed of a clip, simply drag the upper time control to the new location. In this example, I wanted the statue to rotate normally for one second, then ramp up to twice the speed for another second. Then during the third second, the statue should slow down to 50% speed, followed by another variation or two.

To create the first keyframe, move the Time Control marker forward one second and create a new keyframe by clicking on the new keyframe box in the Timeline.

Move ahead to 2:00 and in the Layer Window move the Time-Remap marker to the last frame where you want the change to occur. Making this change will adjust the value graph in the Timeline.

To slow the clip down, move the Current Time marker to the next second, and move the Time-Remap marker back in the Layer Window. In this example, I moved the Time Control marker to 8:00 in the Layer Window and then adjusted the Time-Remap marker to 8:15, which is half the normal speed.

An example of a time-remapped graph in the Timeline.

Continue this process for the remainder of the clip or until you get tired of creating and adjusting keyframes.

Finally, to enhance realism, turn on Frame Blending for the layer to give the illusion of motion blur.

Click image to view final time-remapping clip.

Time-Remapping is a very good way of adjusting and manipulating the apparent speed of a clip for your next commercial project.

When not working deep in the labs of the DMN Central Division testing the latest and greatest software/hardware products Stephen Schleicher can be found at the local university teaching a few courses on video and web production. He can be reached at [email protected]. You can also visit him on the web at www.mindspring.com/~schleicher

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Source: Digital Media Online, Inc.

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