Apple Final Cut Pro 7 - Manual (Page 781)

• Start and End percentages of transition: These sliders allow you to set the starting and
ending percentages of the transition’s visual effect. For example, if you are using an
edge wipe, the default starting percentage of 0 percent places the border of the wipe
all the way to the left of the image, essentially revealing all of the outgoing clip.
The start of an edge
wipe transition
Halfway through the wipe, at the edit point, the wipe is at 50 percent, placing the
border of the wipe in the middle of the picture. You can now see half of the incoming
clip to the left and half of the outgoing clip to the right.
The middle of an edge
wipe transition
At the end of the edit, with the transition finished and the default ending percentage
of 100%, the border of the wipe is all the way to the right, revealing the entire incoming
clip.
Near the end of an edge
wipe transition
781 Chapter 48 Refining Transitions Using the Transition Editor