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How do I get rid of this gain/distortion on my comp?

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Nick Lyons
How do I get rid of this gain/distortion on my comp?
on May 12, 2011 at 3:42:36 am

http://i.imgur.com/H5AWW.jpg

See pic. There's this blue/green noise/gain on my picture and I'd like to get rid of it somehow. Any tips on achieving that?

Thanks!


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Jim Arco
Re: How do I get rid of this gain/distortion on my comp?
on May 12, 2011 at 1:29:16 pm

It looks like you have already done some work on this footage and I wonder if the noise is on the original footage? If not, I would backtrack to determine at which step in your comp the noise originates.

Otherwise, it looks to me like there may be some blown-out highlight at the edge of each stair and also possibly some aliasing artifacts.

The noise exists in all channels, but seems worse in the blue channel. I tried some noise reduction (effects > noise&grain > remove grain) on the still-frame and it helped, but did not totally eliminate the problem. You may also want to try median blur on just the blue channel.

If it is interlaced footage you may want to try reduce interlace flicker.

Jim


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Dave Johnson
Re: How do I get rid of this gain/distortion on my comp?
on May 12, 2011 at 2:24:25 pm

As Jim alluded to, it looks like the noise may originate with some part of the work already done, rather than the original footage. In fact, especially since the extreme areas that you circled seem to be only directly below the text composite, it looks like there may be some extra junk in the alpha channel of the text layer that is worsening the blown-out highlights and aliasing artifacts Jim mentioned. Does it change at all when you turn off the text layer?

I would first resolve that, which may solve the problem completely.

Then, since there is not much color in the staircase, perhaps draw a loose garbage matte around the area with color noise and desaturate it ... not to the point that its completely B&W, but just enough that the color noise is mush less prominent.


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Dave Johnson
Re: How do I get rid of this gain/distortion on my comp?
on May 13, 2011 at 1:36:16 pm

By the way, if you need to use the second method I mentioned, don;t forget to feather the garbage matte so it blends nicely.


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Nick Lyons
Re: How do I get rid of this gain/distortion on my comp?
on May 13, 2011 at 4:00:22 pm

Thank you both for your help! The footage itself was the problem. By garbage matte do you mean a solid layer?


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Dave Johnson
Re: How do I get rid of this gain/distortion on my comp?
on May 13, 2011 at 4:41:55 pm

Sorry ... my brain was in several different places at once when I replied so I actually somewhat mis-used the term "garbage matte", which generally refers to a loose matte to completely cut out portions of a frame. What I was really getting at was drawing a loose mask for the center portion of the staircase, feathering that mask and applying a little desaturation and noise removal to that area only since the rest of the frame is fine (also possibly some minor Curves or Levels adjustments to help with the blown-out highlights in the center of the staircase). That all can be done by drawing a mask directly on a duplicate of the footage layer or by drawing a mask on a solid used as an adjustment layer.


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