UPDATE: 7/15/10: The channel showed another similar video this week on-air and online (it was later removed) which had the same problem. Dr. Forbes, who I recently met at a PSU event, says that the video was not run by any of the senior meteorologists before appearing on-air. If you want to see what a lightning strike REALLY looks like up close, watch this video on YouTube or this one.
UPDATE: See Greg's reply below and our discussion about possible "leaders" in the photo.
I disagree with Dr. Greg Forbes' interpretation of a photo of a "Double Lightning Strike" in Buffalo earlier this month. I hesitated in posting this blog entry because I get comments on my blog every day telling me how everything I post is wrong (I also left him a comment several days before writing this entry, but did not get a reply). Dr. Forbes is an intelligent expert in his field; he understands things about severe weather that few people do. I don't think that either he or the photographer intentionally misled the public; they just weren't aware of this particular "reality-altering bug" in video cameras.
When I saw the picture, as an experienced but admittedly amateur lightning photographer, every bone in my body told me that Forbes' interpretation was incorrect but it took me a few days to amass some proof to present to you, the blog readers. This is the picture (shown here with permission from the original photographer, Kevin Hayes):
Dr. Forbes says that the photo "shows two nearby locations being hit by lightning simultaneously. One is in the center of the photo, while the second is to the right and fainter, just to the left of the tree."
I'll wager that only one strike (not three) is shown and that it is in the background behind the distant trees. Why? Well, first I'm always suspicious of photos that people say show extremely close lightning strikes (less than 100 feet) simply because they are so rare, in fact I only know of one legitimate photo, taken by Kane Quinnel in Australia: this is what a close strike really looks like. Note how bright and wide the strike appears to be.
There's no such thing as a "weak" or "dim" nearby lightning strike as shown in the photo above -- the width of all lightning strike's channels are about the size of your thumb but they appear to get brighter and wider as it gets closer because the brightness increasingly overexposes the film. So if it's dim, it was far away.
My first thought when I looked at the photo was that it was a single frame taken from a video camera recording. This is because I've seen a lot of situations with my own video cameras where the lightning will confuse the camera's hardware and/or software and end up imprinting two frames on top of each other, one offset from the other (think "vertical stabilization" on your old TV).
The incorrect frame is usually purple in color (not sure why). Looking at the photo above, I thought maybe the white line on the upper left was indicative of a second frame so I boosted the color saturation of the photo and voila, the same line exists in the upper right, defining a purple area below, which is the second frame (I have outlined this in black in the image below).
When you move the errant frame upwards, the strike ends up behind the trees in the distance (especially if it was offset left to right, which it may have been). This was confirmed when I got in contact with Kevin and he sent me a second video capture shown below, which shows this effect more obviously. He says it was in fact a video, taken with a Canon G10 Powershot camera. The image below clearly shows the "intra-frame/ ghost" effect, a phrase coined by Doug "Lightning Boy" Kiesling, a professional lightning photographer whom I consulted with via email when writing this entry.
Obviously the lightning wasn't striking on his porch a few inches in front of Kevin (or he wouldn't be alive to tell the story). But if you still don't believe me, it's much easier to see in this capture how the image is offset when you highlight similar areas of the trees at the top:
If you don't believe me, Doug has a whole website explaining the phenomenon). He writes: "The 'ghost channel' artifact is simply an image of the first return stroke channel shifted downward to the bottom of the video frame. The return stroke occurs faster than the camera's shutter and 30 frames per second can resolve, causing the image of the channel to bleed across the lower section of the frame."
Here's another video capture I got from Kevin -- and I would describe this as the only accurate frame from the video, showing the lone lightning strike:
The other "strikes" are what I term "ghost reflections" which may not always be evident without being able to see the whole frame in purple as you can above (here's a similar situation documented on the web). Douglas notes that they can also be reflections from drops of water on the lens, or the lenses or filters themselves (something this guy had trouble with, but which disappeared when he stopped using a UV lens).
Ghost reflections of lightning are a dime a dozen with the cameras I use. Almost every strike features one. If you watch this video I took of lightning in August here in State College PA (taken from a Quicktime movie via my Kodak 650Z camera) you'll see several ghosts. Below is another example of two frames of a video I took (same camera) - clearly the lightning is not striking inside my house behind the window-frame as the highlighted purple areas show.
You want to go old school? Ghost or phantom lightning strikes aren't particular to digital video or even digital cameras. Doug says the phenomenon "occurs with virtually all types of video cameras, from inexpensive consumer models to high-end professional video and television cameras." Here's an example of a ghost from an analog video I took in 1998. The video itself shows that the strike was not in the foreground as suggested by this video capture; the thunder confirms the strike was about a mile away.
DISCLAIMER: Ideas expressed here are my personal thoughts, not the opinion of AccuWeather, Inc. or its employees. Severe Weather Expert Dr. Greg Forbes works for the Weather Channel is a competitor of AccuWeather. Doug Kiesling was a member of WeatherMatrix, which is now owned by AccuWeather.
Comments (1): greg forbes:
The only image I had of the lightning was that first "photo" shown above. It's well known that lightning - by virtue of its short duration and high intensity - can trick both the naked eye and cameras (except probably for the highest-speed cameras used for research), as the blog above points out. The additional video frames shown in this blog clearly show some of these effects, but I'm not sure that what is shown in the "original" photo is all camera artifacts. Stepped leaders and upward leaders don't necessarily have more than a fraction of the current of a return stroke, so different parts of a lightning discharge can be of different brightness. It's possible we are seeing this.
FROM JESSE: Thanks for weighing in, Greg. You are correct that leaders could be dim, I should have mentioned that. I am trying to get a hold of the original video but my initial assessment based on Doug's discussion of leaders vs. ghosts is that leaders are not what we're seeing here.Posted by greg forbes | October 11, 2009 9:42 PM
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