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Why those light lines of fireworks danced like that?

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dannyxu

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Last night, from a distance of about a 1.5 miles across a bay in Vancouver, I used a Canon 70-200mm f2.8L IS with 7D Mk2 mounted on tripod to photograph a fireworks show. In most pictures, light lines of fireworks were not smooth but crooked and danced as if they vibrated. I am sure those lines were in fact smooth, as they really were in other people's pictures. I attached a couple of my pictures (cropped) here to show that.

Lens IS was turned off, tripod was on solid stable ground, wind was not a factor. So what caused the lines dance? I have tried to find an answer online but to no avail. I hope someone in this forum could enlighten me. Many thanks!

p.s. camera setting: focal length 120mm, ISO 400, 0.8-1.3 sd, f7.1

77502a4d8f614301954f6d6a27f54fa7.jpg




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The effect is far more pronounced in the horizontal streams, so it appears to be vertical camera shake. Perhaps the footing of your tripod was not as sound as you thought? At that distance and focal length, even tiny vibrations are likely to be visible. Was there loud music or other noise? That could create vibrations in the camera despite having an otherwise solid footing.
 
Could it be that that is how they actually look? We are not talking about rifled projectiles that are given a spin when they exit a barrel, these are round balls of explosives that explode from a common core.

Perhaps when we view them with the naked eye, because of the persistence of vision(?), they look straight.

Google Fireworks, and look at other images for examples



Westtechill1.jpg
 
Good theory. Certainly possible. OP, are there any other photos taken by others you can share? Such behavior of the fireworks would show up regardless of the gear used.
 
MediaArchivist said:
The effect is far more pronounced in the horizontal streams, so it appears to be vertical camera shake. Perhaps the footing of your tripod was not as sound as you thought? At that distance and focal length, even tiny vibrations are likely to be visible. Was there loud music or other noise? That could create vibrations in the camera despite having an otherwise solid footing.
Click to expand...
 
MediaArchivist said:
Good theory. Certainly possible. OP, are there any other photos taken by others you can share? Such behavior of the fireworks would show up regardless of the gear used.
Click to expand...
 
A thought: was it caused by the vibration of dense near-ground air? The sound of the explosions might also cause the air to vibrate. So this effect should show itself in high-contrast long-distance shots such as those I made. Any insight from you guys?
 
Most likely mirror and shutter shock. The vibrations are mostly upside-down, stronger at the beginning. This is a heavy lens. Did you use collar? Electronic first curtain or MLU? Is your tripod sturdy enough?

Your exposure time is too short and the ISO too high.
 
I did everything possible to minimize camera shake. Please note that those dancing lines dance very regularly throughout the exposure.
 
dannyxu said:
I did everything possible to minimize camera shake. Please note that those dancing lines dance very regularly throughout the exposure.
Click to expand...
The amplitude decreases however while the frequency remains stable. Typical damped oscillator.
 
Sure looks like camera shake. Did you use a remote release? My bet would be that you moved the camera if you did not use a remote release.
 
J A C S said:
Most likely mirror and shutter shock. The vibrations are mostly upside-down, stronger at the beginning. This is a heavy lens. Did you use collar? Electronic first curtain or MLU? Is your tripod sturdy enough?

Your exposure time is too short and the ISO too high.
Click to expand...
You are probably right. The pattern of shutter-induced vibration matches with those dancing lines.

I used collar, no first curtain or MLU, as I wanted to keep shooting without any long interval.

Would longer exposure and lower ISO reduce the effect of such vibration? (or simply for better fireworks image?)
 
Hi Dannyxu,

unfortunately I can only think of camera shake as the direct cause. In the first photo the two large red fireworks not only both oscillate exactly 12 times, the movement is consistent and starts in the same direction (camera moves up, causing an initial U shape to the line).

The exposure time of 0.8s suggests that 15 Hz is either the resonant frequency of your system, or there's a loud low frequency bang caused by something (or both).

cheers

Flakey
 
nopix said:
Sure looks like camera shake. Did you use a remote release? My bet would be that you moved the camera if you did not use a remote release.
Click to expand...
I used a remote. Now I believe it's mirror and shutter shock.
 
It is very likely camera shake which was made more noticeable by the long lens. While I prefer my 7DmkII in almost all situations, fireworks are cleaner with my EOS-M because there is no vibration caused by the mirror flipping up to mar the time exposure.

Test it out by setting it all up again and looking thru the viewfinder at distant subjects (be careful not to touch the camera) while you press the shutter release.

Ben


Disagree without being disagreeable
 
dannyxu said:
J A C S said:
Most likely mirror and shutter shock. The vibrations are mostly upside-down, stronger at the beginning. This is a heavy lens. Did you use collar? Electronic first curtain or MLU? Is your tripod sturdy enough?

Your exposure time is too short and the ISO too high.
Click to expand...
You are probably right. The pattern of shutter-induced vibration matches with those dancing lines.

I used collar, no first curtain or MLU, as I wanted to keep shooting without any long interval.
Click to expand...
Use LV and a remote release. There is very short delay between the shots in this case, just for the shutter to close and open again.
dannyxu said:
Would longer exposure and lower ISO reduce the effect of such vibration? (or simply for better fireworks image?)
Click to expand...
It will hide it better because the trails would be longer. You still need to use LV silent mode (EFC).

A longer exposure does not really overexpose your image unless there are a lot of trails - it just makes them longer.

8 sec

8 sec

15 sec

15 sec



15 sec

15 sec
 
You are enlightening ! Thanks a lot for the advice. Your fireworks pix look brilliant !
 
dannyxu said:
MediaArchivist said:
Good theory. Certainly possible. OP, are there any other photos taken by others you can share? Such behavior of the fireworks would show up regardless of the gear used.

--
Want a roXplosion!?
Click to expand...
While this might be possible, I have yet to see any other people's picture that shows the same effect. Those that are already posted online show no such effect.
Click to expand...
d57730da5dff48c493a298c7a83bcbcf.jpg


handheld on a boat using a 50mm f2.8 with IBIS.

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you need a team to realize your dream
 
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