Dan Robinson
I did some analyzing of the tower lightning video tonight and found a few of interesting features.
Here is a slow-motion, full-screen WMV video clip (1.8MB):
http://wvlightning.com/chase2005/video/leaders.wmv
Upward-propagating leaders are visible prior to all of the strikes on the wide-angle versions of the video.
These features can be differentiated from false 'ghost channel' artifacts common on lightning video. Video is prone to 'ghosting' of the lightning channel on the frame preceding the stroke, but the 'ghost channel' is always shifted downward on the video frame, making the channel appear to be a 'leader' propagating upward very close to the observer, such as in this example from another video:
The 'ghost artifact' is very apparent in this next example frame from another video, where a false 'ghost leader' appears to be striking me in the back!
In the above tower lightning clips, the leaders are in the exact same position and shape as the full stroke on the next video frame, eliminating the possibility of these features being video ghosting artifacts.
Another item of note is two small-scale features on the last return stroke of the second flash. One is a small horizontal leader jutting out from the antenna tip, the second is a downward-reaching branch connected to the main channel.
Contrast-enhancing allows these features to be seen more clearly:
Again, it is not apparent that this is a video ghosting artifact.
It would be interesting to shoot this type of event with a high-speed camera to examine more of these small-scale features that we normally don't get to see.
Here is a slow-motion, full-screen WMV video clip (1.8MB):
http://wvlightning.com/chase2005/video/leaders.wmv
Upward-propagating leaders are visible prior to all of the strikes on the wide-angle versions of the video.
These features can be differentiated from false 'ghost channel' artifacts common on lightning video. Video is prone to 'ghosting' of the lightning channel on the frame preceding the stroke, but the 'ghost channel' is always shifted downward on the video frame, making the channel appear to be a 'leader' propagating upward very close to the observer, such as in this example from another video:
The 'ghost artifact' is very apparent in this next example frame from another video, where a false 'ghost leader' appears to be striking me in the back!
In the above tower lightning clips, the leaders are in the exact same position and shape as the full stroke on the next video frame, eliminating the possibility of these features being video ghosting artifacts.
Another item of note is two small-scale features on the last return stroke of the second flash. One is a small horizontal leader jutting out from the antenna tip, the second is a downward-reaching branch connected to the main channel.
Contrast-enhancing allows these features to be seen more clearly:
Again, it is not apparent that this is a video ghosting artifact.
It would be interesting to shoot this type of event with a high-speed camera to examine more of these small-scale features that we normally don't get to see.
