Video Capture of Stepped Leader
On July 26, 2009, a probable lightning stepped leader was captured on video tape during a short supercell chase. The chase itself yielded nothing more than a wall cloud sighting which was hard to follow in the NJ countryside, and the lightning photographs below.

Video sequence of frames local to the flash. From the frame prior to the stepped leader (labeled Frame -1) until the end of the flash. The total sequence is 12 frames, or ~360 ms in length.

The faint image of the main channel in frames 7-9 is not a camera artifact, since a closer flash later in the trip did not result in the "afterimage" effect. The superheated channel is cooling, and not being dissipated by local winds.

Frame 2 is probably a subsequent stroke in which the dart leader managed to re-energize a few of the larger branches.
 
AniS animation of video frames
 
Stepped leader in Frame 0 is visible in this image. We are heading W on I-195. Subsequent return stroke(s) in Frame +1--no way to tell how many return strokes occurred during this frame, but at least the first return stroke is captured.
Close up of the supposed stepped leader; note the forking of the terminal end, suggesting a branching process.
 Rollover image superimposing the leader on the main flash image from Frame +1. The branching of the leader corresponds to the branching of the main channel. The initial point of the leader is below the cloud base.
   
Conclusion: In the absence of a streak camera or high-speed camera, there is no way to be sure Frame 0 is the image of a stepped leader. It is clearly not a branch from a weak intracloud flash projecting downwards from the cloud base. Also, the leader appears to be a segment of the main channel, even forking at the branch point of the main channel. The evidence is highly suggestive that this is a lucky video capture of a stepped leader.