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In this movie, I'll show you what to do if a single pass of Reduce Noise doesn't quite get rid of all of the noise inside your image. For example, this particular photograph contains a sufficient amount of noise, that even after about the biggest application of Reduce Noise you could possibly apply, we're still seeing a bunch of noise inside the midtones as well as inside the shadow detail. Well, there're a couple of things you can do. One is you can take advantage of the Advanced settings associated with a Reduce Noise filter; and two, you can apply one of the old-school noise reduction functions, such as Dust & Scratches.
So let's start things off by double-clicking on Reduce Noise to bring up the Filters dialog box and I'm going to zoom in on my image as well, so I can see it at 200%. Notice as I click and drag inside the image, I am seeing the unmodified version of the photograph as it appeared before I applied Reduce Noise in the previous movie. All right, now I am going to click on the Advanced radio button to add an additional panel called Per Channel. Go ahead and click on it and drag inside that black-and-white preview right there in order to see the appearance of the active channel, which by default is red.
So let's go ahead and start things off by just cranking up these values here. I'll crank the Strength value up to 10 and I'll take Preserve Details down to 0%, and I will do this on the channel by channel basis. So I will now switch to Green, go ahead and crank it up to 10, take its Preserve Details value down to 0%, and you can see now that we're applying additional applications of both of these values to each one of these channels so far. And we only have Strength and Preserve Details available to us because each channel is a grayscale image.
There is no such thing as Per Channel color noise. All right, so now I am going to switch over to Blue and I'll take its Strength value up to 10 and I'll take Preserve Details down to 0%. And we're getting a very goopy looking image indeed. We have done a great job of getting rid of the noise, but we're also doing a fantastic job of getting rid of the sharp details. So let's go ahead and take the Preserve Details values up a little bit. I'll take the value for the Blue channel up to 5% because blue makes a smallest contribution to detail inside of an RGB photo.
Then I'll switch to Red and I'll take its value let's say up to 25%, and then I'll switchover to Green which makes the biggest contribution in detail and I'll take its Preserve Details value up to 40%. Now the only way you're going to get a sense of the contribution made by your Per Channel adjustments is to go ahead and click OK, because whether you turn off the Preview checkbox or click and hold inside of the Image Preview here, you're seeing the uncorrected version with no Reduce Noise applied.
So I'll go ahead and click OK, not only to update my image, but also to update my High noise image settings. And we'll see this version of the image. Now you're going to have to watch very carefully to see the difference between the before and after. If I press Ctrl+Z or Cmd+Z, this is the before version of the image; if I press Ctrl+Z or Cmd+Z again, this is the after version, so just a little less noise inside of some of the details such as the eye and the midtones, underneath this leg, and so forth. If you want to make a bigger difference which, for this image, we do.
And you want to try one of the old-school noise reduction filters. By going up to the Filter menu, choosing Noise, and either choosing Median or Dust & Scratches, and they both work very similarly. I am going to choose Dust & Scratches because it offers two options instead of just one. If this were Median, we would have no threshold and we would just have this Radius value. And what it does whether we're working in Dust & Scratches or Median is it averages neighboring pixels inside of a radius around an edge. So if I take the value up to six pixels we're scrubbing in six pixel circles around the edges and averaging the results.
So we're gooping up the image tremendously of course as you can see here. Now what I am going to do is scroll down to a lower region of the image. This is a region of that green rock underneath one of the legs. This threshold value which is what you need to Dust & Scratches, this is the only thing that differentiates it from the Median Command. What it does is it preserves the low contrast details inside the image. So for example, if I set the threshold to 40 levels, what I am saying if two neighboring pixels or 40 luminance levels are less different from each other leave them alone which is why we're bringing back the noise, but if the two neighboring pixels are 40 or more levels different from each other, then go ahead and smooth them away according to the radius value.
So we're preserving the low contrast noise and we're getting rid of the high contrast noise along with the detail. And as a result you can see that we have some weird edges around the butterfly's eyes. So I am going to take that threshold value down to 20 levels in order to get rid of some of those problems, not all of them, we'll take care of the rest of them in the next movie. But the great thing here is, for purposes of this image, because it does have so much high contrast noise, it allows us to balance the noise inside the image. So we're preserving some of the low contrast noise, we're getting rid of a lot of the high contrast noise, and that ends up creating a kind of parity.
All right, now I'll go ahead and click OK in order to accept the results of this filter and I will zoom out as well to 100%. Scroll back up to the good detail inside the image so you can see that we've brought back some of the edges, we've messed up other edges, we've completely gotten the rid of the hair on the insect's legs. So if you turn Dust & Scratches off, you can see after a brief progress message, this is the image as it appeared before Dust & Scratches, and then if I press Ctrl+Z or Cmd+Z on the Mac, this is the image as it appears now.
So that's how you smooth away the worst of the noise inside of a high noise photograph. It does come at the expense of the detail however, which is why you need to reinstate the detail using an Edge Mask, and I'll show you how that works in the next movie.
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