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Problems when filming from an airplane


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#1 Simon Bjork

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Posted 07 October 2008 - 03:21 AM

Hello,

I encounterd some problems on a test shoot a few days ago. I was set to film some stock footage from an small airplane. I simply attaced the camera to the middle of the wing, using tejp and some soft materials to keep it as steady as possible. I was shooting with a small HDV-kamera. It all seemed to go fine, until I actually looked at the footage on a larger screen. The problem is that most part of the footage is very jittery, but to me it doesn't feel that it's the camere shaking. It seems like it's some other problem, such as very hard wind directly into the lens or something. What do you think? Does anyone have any experience in filming from a small airplane? The problem was mostly when flying very high, and as you see in the last part of the clip, the jitter isn't as visible when flying low. Any help is very much appriciated.

Link to footage: http://www.veoh.com/...6173321kSPQWpA8
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#2 Alessandro Machi

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Posted 07 October 2008 - 03:33 AM

Did you record audio?

The very last of the three clips looks like there are dropped frames at equal intervals. It also kind of reminds me of the engine sputtering or missing. Maybe the higher up the plane goes the more susceptible it is to thinner air and the engine sputters. If you recorded sound it would be interesting to hear it.

Cool stuff.
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#3 Russell Scott

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Posted 07 October 2008 - 04:01 AM

at a guess I'd say you're using a cmos camera with an incorrect frame rate.


basically a CMOS camera will warp the image if you don't have the frame synced properly with the movement, hence the jitter varying with height (the parallax ground to the plane will result in different apparent motion) ..

if you aren't then ignore what I've said
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#4 Simon Wyss

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Posted 07 October 2008 - 04:48 AM

Hi, Simon

Don't think an airplane's wings are something quiet in the air. They shake and tremble like my grandpa's chin when he laughed.
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#5 Walter Graff

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Posted 07 October 2008 - 08:52 AM

Hello,

I encounterd some problems on a test shoot a few days ago. I was set to film some stock footage from an small airplane. I simply attaced the camera to the middle of the wing, using tejp and some soft materials to keep it as steady as possible. I was shooting with a small HDV-kamera. It all seemed to go fine, until I actually looked at the footage on a larger screen. The problem is that most part of the footage is very jittery, but to me it doesn't feel that it's the camere shaking. It seems like it's some other problem, such as very hard wind directly into the lens or something. What do you think? Does anyone have any experience in filming from a small airplane? The problem was mostly when flying very high, and as you see in the last part of the clip, the jitter isn't as visible when flying low. Any help is very much appriciated.

Link to footage: http://www.veoh.com/...6173321kSPQWpA8


Three thoughts without seeing the actual set up. The movement of the camera is rhythmic in terms of vertical. Since you are affecting the wings performance, namely more burble at the trailing edge , the turbulence would cause the wing to bounce. You will not see it from the plane but the camera does. How can you see it from the plane? Put a glass/bottle of water down in the plane as it flies and you will see waves in the water vibrating at the same frequency as the wings.

Secondly, ever see the ground on a hot summer day. You can see the air currents rise from the ground. Put a camera in the middle of the underneath of a airplane wing and the air turbulence from the leading edge air hitting the camera can cause diffraction since you have a tremendous amount of air being pushed under the wing. The camera would create a vortex of air creating varying diffraction.

And third, while your mount looks good to you, the fact that high speed air is hitting the camera at hurricane speeds means there is some give in the setup causing the slight motion. If you ever saw the classic shot of the traffic sign being blown in hurricanes, it is rhythmic in it's oscillations. You camera will also make a prescribed oscillation without you having something to deflect the air. It's due to the old 'every force has an equal and...' thing. I've seen the same effect on a car hood at high speeds.

As for why it looks better at lower altitudes, there is more apparent movement so the boucing effect is not as clearly visible.

Most camera mounts are under the fuselage rather than the wing as it is an area of far lower pressure than under a wing. Second, most cameras have some sort of semi circular/ wedged air cone in front of them which moves the air around the camera instead of the camera taking the brunt of the air force.
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#6 Chad Stockfleth

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Posted 07 October 2008 - 09:42 AM

I agree with Russell that it looks a lot like CMOS wobble. What camera did you shoot with?

Also, at the end where it looks like there are dropped frames, it also kind of looks like when you shoot with stabilization on while shooting from a tripod where it "snaps" at the end of a pan.

Never done a shot like that so these are just guesses.
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#7 Alessandro Machi

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Posted 07 October 2008 - 11:38 AM

....Also, at the end where it looks like there are dropped frames, it also kind of looks like when you shoot with stabilization on while shooting from a tripod where it "snaps" at the end of a pan.

Never done a shot like that so these are just guesses.....


Excellent diagnosis. That would explain the equal time duration between each "dropped" frame, like a rerack.

That might also explain why the image looks relatively stable when actually there might have been a lot more vibration that was being masked by the camera stabilization being on. Which would explain why the image shakes differently at different heights.

If the stabilization was on, the thing to do is do another test with the stabilization off, at which point all the technical explanations that Walter brought up come into play. I would guess with the stabilization off you might not have a useful picture.

Now, if the stabilization was actually off for your first test, then I have no idea.
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#8 Simon Bjork

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Posted 07 October 2008 - 03:45 PM

Thank you for all replys!

The stabilization was ON!

I cannot believe it. Luckily it was just some tests, but still, now I don't know if I can get an decent image with this setup. The only option is probably to do another test.

It is shot with small Sony HVR-A1 in 1080i.

Do you think I would get better results with the HVX-200 in 50 frames? Will that smooth out the (assumed) bumps?


Cheers
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#9 Allen Achterberg

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Posted 07 October 2008 - 04:00 PM

You can remove that jitter with Virtual Dub and a Free plug-in, Dont remember off the top of my head but it might help. Look into Kenyon Gyro Stabilizers. Try to avoid attatching the camera to the wings if you can.
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Glidecam

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Aerial Filmworks

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