Hi…
when you cut clips together on a timeline:
1) You mark the frames you want to explicitly use
2) Youe place the clips in the timeline.
therefore only the frmaes you explicitly chose are exposed during playback.
If you use transitions between clips on a single track
you will always be exposing frames that you did not explicitly mark in the shot originally.
If you apply a 1:00 dissolve as centered on the cut that means:
Shot A > Dissolve > Shot B
1:00 divided by 2 = :15 frames (assumes NTSC)
so this means that
Shot B will actually start to display 15 frames before the cut point, using 15 frames of media before the actual in point you marked
Shot A will actually extend into Shot B by 15 frames, exposing 15 frames of media beyond the acutal out point you marked.
This is why you are seeing media that you didn’t orginally mark being expose based on your marks…
You’ll need to
a) Change the alignment of the transition
b) Change the Length of the transition
c) Some combination of the 2
Hope this helps…
Alex