Turning Down the Volume - Adobe Photoshop

Between the low light and the JPG compression, the noise is hideously apparent in this image. How do you reduce the amount of noise?

  1. Open Aquarium.tga, whose noise you can see in Figure below.
  2. The noise in the blue background is painfully obvious

  3. Duplicate the background layer by pressing Command+J(Win: Ctrl+J).
  4. Applying a Gaussian Blur until the graininess is just blurred out is what you do next.

  5. Make sure you are on the duplicated layer and go to Filter > Blur >Gaussian Blur.
  6. Set the Radius to 2.4 pixels.You can see my values in Figure below, but experiment to get a feel for the level of blur that works for you.
  7. As noisy as this is, you can’t blur it completely

  8. Go to the Layers palette and switch the Layer Blend mode from Normal to Color.
  9. Figure below has the composite image use the luminance from the lower layer and the color info from the top layer. Quite a bit of noise still exists. Looking at the RGB channels can help you see where this is most obvious.

    The noise is much reduced, but still obvious

  10. Switch to the Channels palette and take a look at the individual channels.The red channel, which you can see in Figure below, is not too bad.
  11. The red channel looks fine.

  12. Click the green channel. The green channel in Figure below isn’t too bad either.
  13. The green channel looks okay, too.

  14. Click the blue channel.
  15. Ah ha! It looks like you have found your culprit in the blue channel! Check it out in Figure below. You know the culprit, but doing anything right now only applies the change to your selected layer. You want to apply it to the composite image

    It’s very common for the blue channel to hold the most noise.

  16. Switch back to the composite image by clicking the channel layer marked RGB.
  17. Flatten the image by going to the Layers palette and choosing Flatten Image. See Figure below.
  18. You need to flatten the image.

  19. Reselect the blue channel and apply the Gaussian Blur until the painful freckles are reduced to smudges.
  20. Don’t worry too much about its blurriness, the likes of which Figure below shows. The point is to try to eradicate the noise. Because you’re only blurring one channel, you can go a little more blurry on this one.

    I pulled out the Layers palette to remind you to apply the blur to the flattened image.

  21. Now take a look at the composite.
  22. Much improved especially when you compare it to the original image! You can see it in Figure below. How does this compare in noise tests?

    Compare the before (left) and after (right)

  23. Run the Find Edges filter on only the before and after.

See how they look in Figure below. The after image on the right is remarkably cleaner than the original

I desaturated the results so as to not be distracted by the colors. Even though you didn’t run the Saturation or Unsharp masks, Find Edges shows quite a difference between the two.


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