How do you reduce noise and preserve edge details at the same time?

What You’ll Need:

>> Adobe Photoshop Elements or Photoshop
>> 10 Minutes

Difficulty: Hard

Elements and Photoshop have a Reduce Noise filter that looks like it offers all you need to reduce the noise in high ISO images without sacrificing too much fine detail. In practice, though, it’s not so easy, despite the sophisticated controls.

You can push the Reduce Color Noise slider right up to 100% without sacrificing sharpness but while this can help, it’s only with older cameras that it makes much difference – newer models do a pretty good job of suppressing color noise right from the start.

BEFORE: How do you reduce noise in areas without sacrificing detail?

AFTER: By using a smart combination of filters and mask layers, that’s how!

The real problem is luminance noise, and this is what the Strength slider fixes. Unfortunately, as soon as you begin to drag it to the right, you’ll start to see a trade-off in fine detail. And long before all the noise has disappeared, the loss in definition is becoming unacceptable.

The Preserve Details slider (and the extra Sharpen Details slider in Photoshop) are designed to counteract this, but they also make the noise more prominent at the same time. What you really need is a process that reduces noise in areas where there is no real detail, but leaves highly detailed areas alone. That’s what sophisticated noise-reduction tools attempt to do, but without much success. The fact is that you can do a much better job yourself, and while the steps in our walkthrough might look complicated, it’s basically a two-step process.

First, you apply the Noise Reduction filter to a duplicate layer to bring the noise down. Second, you use the Find Edges filter to pick out the details in the picture, and then use this to create a mask for this, the Noise Reduction layer. Apart from a couple of tweaks to improve the effectiveness, that’s all there is to it. Your images look smoother, but just as sharp as they did before.

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How to Get Smarter Noise Reduction in Photoshop

• View the full image

  Duplicate the Layer

  This technique relies on a layer mask, so don’t apply noise reduction to the image layer directly. Instead, duplicate the layer by dragging its thumbnail onto the New layer button at the bottom of the Layers palette. It’s a good idea to name your layers as you go along.

• View the full image

  Reduce Noise Filter

  Now apply the Reduce Noise filter to this duplicate layer. Push the Reduce Color Noise slider right up to maximum, but leave the Preserve Details slider at 0%. Now push the Strength slider as far as you need to in order to get rid of the noise in the image.

• View the full image

  Duplicate This Layer Too

  Now you need to create a mask to protect the edges in the picture, so duplicate this new layer, and call it "Find Edges layer" to distinguish it from the others. The fact that noise reduction has already been applied will improve the results in the next step.

• View the full image

  Find Edges Filter

  Now apply Filter > Stylize > Find Edges. This picks out strong edges in the image but leaves even-toned areas alone. It will also pick up some "edges" in noisy areas of the image, but that’s not too big a problem and it’s possible to filter this out to a degree later on.

• View the full image

  Select and Cut Layer

  Select the whole of this layer. You’ll see the layer enclosed by a "marching ant" selection. Now use the Edit > Cut command (or command+X). The image disappears, leaving an empty layer. You don’t need this layer any more, so you can delete it.

• View the full image

  Create a Layer Mask

  Select the "Noise reduction" layer created earlier, and click the Add layer mask button at the bottom of the Layers palette. Click the mask to select it. It will appear white, but use the Edit > Paste command, and the copied "Find Edges" layer will be pasted in.

• View the full image

  Check the Result

  Click back on the noise reduction layer: the layer mask is no longer being viewed directly, and you can see its effect. It’s now masking the edges in the image so that only the even-toned areas are showing the noise-reduction effect. Now to strengthen it a little....

• View the full image

  Adjust the Mask

  Select the layer mask. Adjust the Levels, dragging the black point slider to the right, just past the start of the histogram — this increases the contrast and maximizes edge-protection.

• View the full image

  Quick Tip

  This process can slightly increase noise even in smooth-toned areas, but there’s a solution – simply apply the Reduce Noise filter to the layer mask you’ve created. It won’t have much effect on the masked areas, but it should help clear up any noise showing through where the mask itself is a little noisy.

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