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Monday, May 14, 2012

••◊ Noise reduction in After Effects, part 2

A while back I wrote about doing some noise reduction in After Effects to clean up footage I shot on the 5D mark II at ISO 3200-6400.  Yes, it was non-ideal but I didn't have any lights with me and wanted the shot.  Such is life.
I went back and cleaned up the footage a little more using a slightly improved configuration of noise reduction techniques; thus this blog post.  First let's start out with the original noisy image as shown below.  If you click on the image you'll see oodles (the technical term for it) of noise on the wall just to the left of his bicep.

In the previous blog post I mentioned blurring the CMOS chroma noise by using three After Effects...well effects (It sounds funny if you say "After Effects effects, no?)  We'll start with the usual chain: Channel Combiner with RGB to YUV, Channel Blur with green/blue linked and set to about 20-ish (generic starting point), and another Channel Combiner with YUV to RGB.  This creates a monochrome noise reminiscent of film grain.  Not bad, but not great.  Click on the picture below to see the change in noise, especially in that same section of wall.

Now we'll add the secret sauce to complete the recipe.  In the "Noise & Grain" group of effects there's an effect called "Remove Grain."  The trick with this is that the effect needs to be treated with kid gloves, otherwise you end up with the dreaded plastic alien skin and latex clothes with no texture.  Because the majority of the noise was already obscured with the previous three effects, I found that I could set the "Noise Reduction" parameter to 0.2 and avoid these issues.  See the picture below.

No, it's not a perfect solution.  I'll be the first to admit that.  However, it's a lot better than where the footage started off.  Detail in his skin and clothes is pretty much all still there.  The main issue I have with this configuration is that the video takes a long time to render out.  Hope this works for you as well.

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