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Flickering in welding footage

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Hannah Hill
Flickering in welding footage
on Mar 5, 2015 at 7:08:33 pm

We are currently working on a project that involves filming welding footage, and we are getting a really bad flicker in our footage. We are currently shoot with a 5D mark iii and a c100 mark ii, and we are shooting at 60p with extremely high shutter speeds (over 1000). Do you know of any way to get rid of the flicker in our current footage or how to re-shoot it without the flicker? I really appreciate it!


Here's a link to what I mean: https://vimeo.com/121382543
the password is: 1234


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Tero Ahlfors
Re: Flickering in welding footage
on Mar 5, 2015 at 7:20:14 pm

Looks like a rolling shutter problem. You should rent a camera with a global shutter.


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Hannah Hill
Re: Flickering in welding footage
on Mar 5, 2015 at 7:29:41 pm

I thought you can get rid of rolling shutter by turning the shutter speed up high.


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Steve Crow
Re: Flickering in welding footage
on Mar 5, 2015 at 11:11:27 pm

If using a very high shutter speed, try instead sticking to the 180 degree rule and selecting a shutter speed as close as you can get to 1 over twice the frame rate, so if filming at 24fps then you would want the closest shutter speed to 1/48 which is usually 1/50th of a second.

I think the flickering of the welding torch is interacting with your shutter speed and frame rate in some fashion....perhaps something similar to the rolling bars effect you can get when filming under fluorescent lights....just my thoughts but I'd experiment to find the answer - it's the only way to know for sure

Steve Crow


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Tero Ahlfors
Re: Flickering in welding footage
on Mar 6, 2015 at 7:15:13 am

The shutter speed doesn't affect the way the sensor is creating the image. Which is sweeping the sensor vertically.


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John Baumchen
Re: Flickering in welding footage
on Mar 24, 2015 at 2:28:02 pm

the arc of the welder is a noise generator that is affecting your camera's electronics. These generate HUGE amounts of EMI/RFI (electromagnetic interference/ radio frequency interference), close to the arc.

What is likely happening is that these EMI/RFI waves are passing thru the housing of your camera, hitting the copper traces on the printed wiring boards, (which act like antennas), and the EMI/RFI induces unwanted electrical currents into the camera circuitry, causing the noise problem you're encountering.

One way to help reduce it is to move the camera farther away from the source, or get some phosphor-bronze mesh, wrap it around as much of the camera housing as possible, and ground it. This creates something of a Faraday Cage, (an RF shield), that should allow you to place the camera closer to the welding.

Cheers.


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