Apple Final Cut Express 4 - Manual (Page 790)

790 Part IX Effects and Color Correction
The simplest speed change you can make to a clip is a constant speed change. You do
this using the Speed dialog.
To change the playback speed of a clip by a constant amount:
1 Select a clip in the Timeline, or move the playhead over a clip in the Timeline.
2 Do one of the following:
 Choose Modify > Speed (or press Command-J).
 Control-click the clip, then choose Speed from the shortcut menu.
3 Select speed options for the effect you want to create, then click OK.
 Duration and Speed fields: You can modify the clip’s marked duration or speed
percentage. Unmodified clips have a clip speed of 100 percent. These fields work in
parallel; changes to one of these settings are automatically reflected in the other.
 Reverse: Select this checkbox to make the clip play in reverse, using any speed
specified by the above controls.
 Frame Blending: Select this checkbox to smooth the apparent motion of a clip
playing back at slow or fast speeds.
The clip’s duration in your sequence changes, getting longer or shorter depending on
the new speed you specified.
Smoothing Slow Motion Using Motion Blur
Although using frame blending is an excellent way to smooth out the apparent
motion of a slow-motion clip, extremely slow speeds such as those below 20 percent
can still result in strobing. To further minimize this effect, you can use the Motion Blur
attribute in the Motion tab.
Drag the Samples slider to the right until you achieve the amount of blur you need to
cover the strobing of your clip (the higher the Samples setting, the longer rendering
takes) and then adjust the % Blur setting until you strike a good compromise
between the sharpness of the clip and the smoothness of the motion.
Note: Motion Blur is not a real-time effect and in fact can be quite render-intensive at
its higher settings. For this reason, you may find it best to adjust the speed and
duration of your clip with Motion Blur turned off, turning it on again only for the final
render. To turn off Motion Blur without individually removing it from every clip, you
can deselect the Motion Blur control in the Motion tab of Viewer.