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Video Noise - how to hide it

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mark thompson
Video Noise - how to hide it
on Jan 26, 2015 at 4:31:48 pm
Last Edited By mark thompson on Jan 27, 2015 at 9:38:27 am

Hi,
I did a shoot last week in a studio. There was plenty of light available. However when the clips were green screened in AE the noise on the darker parts of the picture were very pronounced.

Looking into it further there was noise on the all the clips, it was just more visible in dark areas.

I did do one shot with just the green screen in it and that is noisy. I've uploaded a clip in: https://www.dropbox.com/sh/xluydrywueb60wa/AAAaWfwplZpcFlM9U9lkbMJfa?dl=0

A good way of seeing this is to use Sony Catalyst Browse. View the clip, Adjust Color and then look at the Histogram. It is amazing how live it is considering it is just a static shot.

But what could be causing it? Is it the Camera (PMW 200)? Are studio lights interfering? There were timecode and SDI cables plugged in, could it be interference coming from those?

I was shooting 50Mhz, 422, 25P.

I'm interested in tips and techniques to reduce noise as much as I can. Also what would you in AE/PPro to remediate footage.

Thanks

mark


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Michael Slowe
Re: Video Noise - how to hide it
on Jan 27, 2015 at 12:24:58 pm

Silly question I know, but what was your gain setting? Presumably all your settings were on manual and you may have set the gain too high by mistake. I always set mine to -3 providing there is enough light and in your case you say that there is.

Michael Slowe


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mark thompson
Re: Video Noise - how to hide it
on Jan 27, 2015 at 12:44:40 pm

Michael,
my gain was on 0db, i.e. the default low value.
There was plenty of light on the day, although it was mainly on head/shoulders/body and less so on the legs.

I will give that setting a go, is the idea that you dim down the dark bits so you can't see the noise?

mark


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Michael Slowe
Re: Video Noise - how to hide it
on Jan 27, 2015 at 2:06:15 pm

Mark, always go for the lowest gain that the light allows. Set -3 as your default. Gain is an electronic method used to boost the exposure when your aperture alone can't do the job. It's artificial and is bound to degrade the picture to some extent. However, it is all a matter of compromise, and it does mean that you can get a picture of some sort by increasing the gain in really poor light. Others on this forum, with more technical knowledge than me will doubtless explain.

Michael Slowe


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mark thompson
Re: Video Noise - how to hide it
on Jan 29, 2015 at 4:00:42 pm

An update on this problem.
I did a test on a slightly newer pmw-200 and it had the same noise (sensor noise)level as mine - so it is not a defect in my camera.
The gain on both cameras was 0db, I've still to try -3db.

After looking at the problem I now believe my main problem is that Keylight (in After Effects) is a contributing factor - so I will pursue that over in their forum.

On the sample I posted you can see the noise as a shimmering effect. When I try to get a key you see blotches rather than just the pixels.


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Clint Fleckenstein
Re: Video Noise - how to hide it
on Feb 4, 2015 at 5:20:03 pm

When I've run into noise issues in the past with XDCAM EX footage and Keylight, I've used the following:

- Key the footage in Keylight. Don't soften the edges.

- Use the keyed footage as a track matte for the original footage.

- Fine tune the edges using AE's matte tools.

I know it's not as convenient as doing it all in Keylight, but it's worked for me on multiple occasions. I hope it works for you.

Cf


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mark thompson
Re: Video Noise - how to hide it
on Feb 5, 2015 at 3:17:54 pm

Clint,

thanks, I'm trying that today.

mark


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Roger Bansemer
Re: Video Noise - how to hide it
on Mar 26, 2015 at 11:07:05 am

I had that same problem with grain on a shoot here in my studio and I couldn't figure out why. I reset my camera setting to the default on the menu.
BUT... to answer the question, I used two Boris plugins to fix the problem. One is the BCC Magic Sharp and the other was the BCC Noise Reduction.
It absolutely fixed it. In fact is saved the entire shoot which was for PBS.

Roger Bansemer - PaintingAndTravel.com


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Bob Cole
Re: Video Noise - how to hide it
on Apr 6, 2015 at 11:57:19 pm

Mark, in Keylight there are a couple settings which can make a difference in noise in dark areas.

Look at Keylight/Screen Matte/Replace Method, and experiment with Soft and Hard Colour, etc.

Bob C


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