Lightning Artefacts on Video

robotriot

New Member
Hello everyone,

I stumbled upon this site today and find that whole debunking process you guys are involved in very interesting. I'm especially interested in explaining visual phenomena and I have something that I always wondered about. Maybe one of you can explain what exactly is going on here.

These are still images from a video of a thunderstorm I recorded with a cheap digital camera a couple of years ago. After taking a closer look at the lightning I recorded, I noticed that sometimes the lightning seems to be in front of trees and buildings, which means it would have struck about 100-150 meters from my window, several times. I don't know that it looks like when lightning actually strikes the ground and when observing the lightning, I always felt like the lightning struck much further away, behind the trees. So I was thinking it's probably some sort of visual artefact (like the frame in the middle row to the right, where the lightning is actually cut off entirely). Is it some form of double exposure? Can anyone explain what exactly is going on here technically?

lightning.jpg
 

deirdre

Moderator
Staff member
in your last two photos.. what am i looking at? they are the exact same lightning bolt. ?
 

robotriot

New Member
in your last two photos.. what am i looking at? they are the exact same lightning bolt. ?
Yea, they are from the same lightning bolt. In the frame on the bottom left, it appears to be in front of the trees while in the second one, you can only see a short bit at the bottom that is cut off suddenly, and the rest of the bolt appears to be in the sky behind the trees.
 

deirdre

Moderator
Staff member
and the rest of the bolt appears to be in the sky behind the trees.
theres a little bit in front of the trees on the bottom. i'm just guessing but if the camera was snapping that fast to catch a lightning bolt twice in the exact same position.. could it be something to do with the sensor not being able to reset fast enough?

eventually a "camera guy" will read this post and maybe be able to give you an explanation. :)
 

robotriot

New Member
theres a little bit in front of the trees on the bottom. i'm just guessing but if the camera was snapping that fast to catch a lightning bolt twice in the exact same position.. could it be something to do with the sensor not being able to reset fast enough?

eventually a "camera guy" will read this post and maybe be able to give you an explanation. :)
I was hoping so :)

I've uploaded the video in its entirety for completeness sake to Youtube: (at the time I recorded a couple of minutes of the thunderstorm and just edited out all the non-lightning bolt footage).
 

deirdre

Moderator
Staff member
I was hoping so :)

I've uploaded the video in its entirety for completeness sake to Youtube: (at the time I recorded a couple of minutes of the thunderstorm and just edited out all the non-lightning bolt footage).
nice vid. very cool. quick question.. so are those screen grabs from the video?
 

Ray Von Geezer

Senior Member
Nice video!

What camera is it? Could it possibly have a compression issue that's causing the bolt to be duplicated in picture 5, or were you behind glass?

Ray Von
 

robotriot

New Member
Nice video!

What camera is it? Could it possibly have a compression issue that's causing the bolt to be duplicated in picture 5, or were you behind glass?

Ray Von
The camera model used was a Sanyo XACTI VPC-J2EX. The video was recorded from behind a closed window, yes.
 

Pete Tar

Senior Member
What is the anomaly exactly? Lightning is known to discharge from the ground up, if that's what it is. Or is it the in front/behind thing happening?
 

deirdre

Moderator
Staff member
This kinda sounds like the explanation (not that i can follow it really :) nice full article exxplanation though.


i noticed in one photo the bottom seems to match the top a bit too nicely... maybe this is the "ghost image" ?
purpleligtning.jpg



edit add.. and just for educational purposes, i googled "lightning photos purple artifacts", then "images" and clicked on teh first photo that looked like a purple artefact. basically i got lucky.
 

Mick West

Administrator
Staff member
I think deirdre has it. Here's a sequence of the frames, just looking at the region on the right of the frame:


Notice the bolt at the bottom of frame 105 is basically the same as the bolt at the top of frame 110, clearly it's just an ghost image of the lighting in the sky.



It's a little confusing as the "ghost" image appears to happen before the real image. But that's just a result of the rolling shutter. In 105 the shutter had already got 3/4 of the way down the image before the lightning started.

Here's a boosted version of frame 105, which clearly shows the rolling shutter effect:


There's a lot more discussion of rolling shutter here:
https://www.metabunk.org/solved-strange-beam-of-light-over-mayan-temple-and-florida-lightning-rolling-shutter-artifact.t3244/
With an example of how it can get a segment of the lighting bolt:
 
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Mick West

Administrator
Staff member
More specifically, I download the video from YouTube using an OSX program called "Downie"
http://software.charliemonroe.net/downie/

I then use the Quicktime viewer to single-step through it using the arrow keys. I usually use the latest version, but sometimes use Quicktime Viewer 7, which lets you display the frame number
 

robotriot

New Member
Thank you deirdre and Mick West for explaining the phenomenon! I was pretty sure it had to do something with the way video cameras worked, but the link that deirdre posted explains it perfectly. Good find!
 

deirdre

Moderator
Staff member
Thank you deirdre and Mick West for explaining the phenomenon! I was pretty sure it had to do something with the way video cameras worked, but the link that deirdre posted explains it perfectly. Good find!
useful topic. :) plus i learned about grabbing video frames! dont know when i'll ever need them, but how cool is that?

sorry i mucked up your thread with my video/computer illiteracy.
 
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