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Help with video phasing shot on EX1 with HMI Lighting

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Brian Brough
Help with video phasing shot on EX1 with HMI Lighting
on May 23, 2009 at 7:21:28 am

I shot a project on the EX1 with HMI lighting and there is a constant phasing/flicker with subtle thick lines going up the image throughout the footage. I've read about possible solutions during shooting since then, but I wonder if there's anyway to eliminate or reduce the phasing effect in post production so I can still use the existing footage. Any help would be great.


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olof ekbergh
Re: Help with video phasing shot on EX1 with HMI Lighting
on May 23, 2009 at 12:15:49 pm

I shoot with HMI's all the time. I have never seen this.

More details would help.

Was there florescent light in shoot as well?

What was your shutter speed?

Can you link to some footage that shows this (Vimeo or similar)?

Olof Ekbergh


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Brian Brough
Re: Help with video phasing shot on EX1 with HMI Lighting
on May 26, 2009 at 5:48:50 pm

There weren't any flourescent lights in these scenes but it was lit using HMI's, Kino Flos, and tungstens. The shutter was off with 180 degree angle. Here's a link to a couple of the shots. The phasing is subtle but can be seen and gets annoying over time.

Thanks!

http://virb.com/mmscreeningroom/videos/3086655


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Brian Brough
Re: Help with video phasing shot on EX1 with HMI Lighting
on May 26, 2009 at 6:13:03 pm

Here's another longer clip where it may be easier to see. If you scroll through the video quickly, you can see the phasing/lines much easier.

http://virb.com/mmscreeningroom/videos/3086934


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olof ekbergh
Re: Help with video phasing shot on EX1 with HMI Lighting
on May 27, 2009 at 11:37:07 am

That looks like RF interferance.

Were you close to any large antenna or equipment that may have emitted RF?

If you set up your lights somewhere else, another location is the phasing present?

Also try shooting with just one light at a time to see if there is one light causing this effect.

Olof Ekbergh


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Brian Brough
Re: Help with video phasing shot on EX1 with HMI Lighting
on May 27, 2009 at 5:49:25 pm

The phasing is present in most of our shots in different locations with different lighting, but only in scenes with HMI lighting. Most of the time, it's not noticeable unless it's sped up, but these shots I posted are more evident.

I guess my main question is whether or not there's a way to eliminate or minimize this in post so it's not as noticeable?

Thanks!


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olof ekbergh
Re: Help with video phasing shot on EX1 with HMI Lighting
on May 27, 2009 at 6:37:22 pm

I have 20-30 hrs of footage shot with HMI and the EX3 all 1080 60i, and I have none of this in any footage.

Are you always using the same lights?

Olof Ekbergh


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olof ekbergh
Re: Help with video phasing shot on EX1 with HMI Lighting
on May 27, 2009 at 6:44:26 pm

As far as fixing in post.

Yes it could be done in AE.

You would build a filter effect that neutralizes the phasing including a soft border (probably a brightness adjustment or maybe levels), then make it travel with the "disturbance".

If it is really even and always the same you could then loop it.

It may not be that bad, but if it varies in intensity and frequency it could take a while.

Olof Ekbergh


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