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Using the Median filter and Dust and Scratches

From: Photoshop CS3 Sharpening Images

Video: Using the Median filter and Dust and Scratches

In this exercise we are going to talk about some very basic but useful functions that allow you to average and smooth away noise and other bad details inside of an image. Now these are the most primitive filters that you can work with, but it turns out they can be useful. So I want you to get a sense of what you have available to you in your filtering arsenal. So I am going to start things out, working in that same image that we saw in the previous chapter; this one is called Sammy shake.jpeg. It's a picture of my youngest, Sammy, and it has got a little bit of camera shake going on and he is moving as well and it's a long shutter speed of course with out a flash.

Using the Median filter and Dust and Scratches

In this exercise we are going to talk about some very basic but useful functions that allow you to average and smooth away noise and other bad details inside of an image. Now these are the most primitive filters that you can work with, but it turns out they can be useful. So I want you to get a sense of what you have available to you in your filtering arsenal. So I am going to start things out, working in that same image that we saw in the previous chapter; this one is called Sammy shake.jpeg. It's a picture of my youngest, Sammy, and it has got a little bit of camera shake going on and he is moving as well and it's a long shutter speed of course with out a flash.

So that's why we have got some motion blur going on here. And this image is found inside the 03_sharpen_filters folder. So even though we are in Chapter 4, go to the 03 folder to find this one. I am going to go up to the Filter menu and I am going to choose this command right there, Noise, which presents you with a series of filters that either allow you to add Noise to an image, which is what Add Noise does. You can kind of get a little bit of a grunge effect if you want to. Well that's kind of an old school way to use Add Noise. These days people primarily use it to try to match digital noise.

So if you have two different images that you are trying to merge together and one has more noise than the other then you then use Add Noise in order to match the noise. You can also use Add Noise in areas that you've smoothed over with the Smudge tool or the Blur tool or something along those lines. You can add the noise back in if you use the Liquify filter. That can end up getting rid of noise inside of an image, including overly smooth transitions, and you can re-invoke the noise using the Add Noise command. We are going to focus on the tools, however, that allow you to get rid of noise, starting with the most essential tool of them all, which is the Median command right here.

Notice that I have given it a keyboard shortcut, once again using the Keyboard Shortcuts command under the Edit menu. And this command strictly averages neighboring pixels. So again it's going through and scrubbing with the scrubbing bubbles; it's going through and scrubbing the image one pixel at a time, nanoseconds by nanoseconds. It's averaging whole groups of pixels inside that bubble according to your Radius values. So the higher Radius values will give you more averaging inside the image and more smoothing as well and more or of a porcelain effect.

So notice I am taking the Radius value up one pixel at a time here by pressing the Up arrow key as I am talking to you, and I have now got the Radius value up to 10 pixels and we get a very smooth effect indeed here. I will go ahead and click OK in order to accept that modification. And then just to give you a sense of how this command reacts with something like sharpening, I'll go to the Filter menu, choose Sharpen and choose the Smart Sharpen command and then we will go ahead and apply a pretty heavy pass of sharpen. Lets make no bones about it here.

I will raise the Amount value to 500% and the Radius value, lets take it up to 4 pixels. We are removing Lens Blur inside of this image, leave More Accurate turned off for this specific effect right here. And I will go ahead and click OK and you can see that we now have this plastic wrapped boy effect at this point. We do have a fair amount of color artifacting going on. You can see these wild color rainbows going along his ear and inside of his eyes as well. And if you want to get rid of that, then you would just go up to the Edit menu choose Fade Smart Sharpen; just like we saw in the previous chapter and you would go ahead and change the blend mode to Luminosity in order to blend the new sharpening effect with the old color information.

Then you would click OK, so in other words we are keeping the sharpened luminance information and we're blending it with the unsharpened color information and we get this effect right here. So it's not the least bit- I would not say this is an effect for the sake of realism. It is not a realistic effect at all, but it just gives you a sense how the tools work and I will show you how to make realistic use of the Median function in a future exercise. Alright so that is Median. I want to compare it to another function very briefly here, that's under that same submenu.

So lets go ahead here inside the History palette and lets restore the original version of Sammy by clicking on Open and then I am going to go ahead and close History for a moment, so that we can see that what we are doing again. I am going to go to the Filter menu. I am going to choose Noise and I am going to choose the command that is almost exactly the same as Median, which is Dust & Scratches. Now as I would like to say Dust & Scratches is useful for neither. It's no good for removing dust, it's no good for removing scratches; in fact it's really good at leaving behind dust and scratches because what it does is it medians, it applies to the Median command, so it averages pixels that are very different from each other while leaving pixels that are very close to each other, in terms of luminance information, the same as they were before.

So it averages the image, it averages most of the information in the image while leaving the noise behind. So let me show you what I am talking about. I am going to go ahead and choose the command and lets go ahead and take that Radius value, which is just right out of the Median Ccommand. We will take it up to 10 pixels just like before. If I was to compare that with the effects of applying Median with 10 pixels, it would be identical. You would see the exact same effect on the screen here. The difference is when we start raising the Threshold value. So I am going to take this Threshold value up and again I am raising it by pressing the Up arrow key and as I raise this Threshold value we are starting to bring back the noise inside of the image.

Do you see that? I am going to go ahead and zoom in on this image a little bit, o that we can see it in more detail here on screen, inside the video that is. And the higher I take this Threshold value the more of the noise I bring back. So with a Threshold of 17 luminance levels, I am saying go ahead and average any pixels that are at least 15 luminance levels different from their immediate neighbors. If they are not at least 15 luminance levels different, don't average them. So in another words average the big differences inside the image, but don't average the small differences; leave the noise behind.

Now that may seem like a really strange thing to do. Certainly for sharpening purposes it's not the effect we want, it is the opposite of the effect we want. The reason Dust & Scratches exists and the reason it can be useful is because it allows you to basically smooth over image details inside of an image, especially if you want to paint them back in. If I was to take this on to an independent layer and then paint some of these details away so that they become smoother. But if I wanted to leave that natural organic digital noise behind, the noise that was captured by the digital camera, then I would use this command.

And I actually have an example of this inside of my Photoshop CS3 One-on-One series. You can check out a way to make great use of the Dust & Scratches function. I am not going to show you that here though, instead we are going to focus on things that help us sharpen and Dust & Scratches ain't it. What we need is something that allows you to blur away either average away or blur away the noise inside of the image and leave the good detail behind and we are going to see examples of such functions in the very next exercise.

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This video is part of

Image for Photoshop CS3 Sharpening Images
Photoshop CS3 Sharpening Images

115 video lessons · 17006 viewers

Deke McClelland
Author

 
Expand all | Collapse all
  1. 50m 30s
    1. Why every image needs sharpening
      2m 38s
    2. Understanding the effects of sharpening
      5m 26s
    3. Understanding the mechanics of sharpening
      4m 19s
    4. Understanding sharpening and gradual transitions
      3m 21s
    5. Understanding sharpening and noise reduction
      4m 0s
    6. Understanding amount and radius
      7m 50s
    7. Measuring your screen resolution
      6m 19s
    8. Using reliable zoom ratios
      5m 30s
    9. Calculating the actual print size
      4m 54s
    10. Gauging the ideal sharpening settings
      6m 13s
  2. 59m 31s
    1. Everyone knows you sharpen last (and everyone is wrong)
      1m 8s
    2. Understanding the conventional sharpening workflow
      5m 4s
    3. Flattening and saving to TIFF
      6m 39s
    4. Downsampling (and why you shouldn't upsample)
      6m 8s
    5. Understanding last-step sharpening
      6m 44s
    6. Recognizing problems with the conventional workflow
      9m 38s
    7. Erasing sharpening with the history brush
      4m 30s
    8. Using alternative sharpening workflows
      2m 37s
    9. Sharpening a scanned photograph shot on film
      2m 45s
    10. Sharpening a digital photograph
      3m 6s
    11. Sharpening specific details
      3m 43s
    12. Finding broad workflow conclusions
      2m 49s
    13. Learning that technique trumps timing
      4m 40s
  3. 1h 27m
    1. Comparing and contrasting neighboring pixels
      1m 6s
    2. Using the Gaussian Blur filter
      4m 25s
    3. Using Gaussian luminance distribution
      4m 47s
    4. Using the Unsharp Mask filter
      4m 54s
    5. Understanding the history of Unsharp Mask
      3m 51s
    6. Building your own USM with Gaussian Blur
      7m 35s
    7. Using the Smart Sharpen filter
      7m 35s
    8. Compensating for camera shake
      8m 50s
    9. Building your own Smart Sharpen with Lens Blur
      6m 59s
    10. Using directional sharpening with Emboss
      9m 13s
    11. Using Smart Sharpen extras
      8m 56s
    12. Using Convolution Kernels for more accuracy
      7m 8s
    13. Using the High Pass filter
      7m 32s
    14. Using Luminance Sharpening
      5m 5s
  4. 2h 14m
    1. Smoothing filters, smart objects, and masks
      1m 25s
    2. Using the Median filter and Dust and Scratches
      7m 7s
    3. Using Smart Blur and Surface Blur
      6m 12s
    4. Using the Despeckle filter
      8m 17s
    5. Softening flesh tones selectively
      10m 15s
    6. Using the Reduce Noise filter
      7m 27s
    7. Combining smoothing and sharpening
      8m 24s
    8. Making an image into a smart object
      9m 24s
    9. Applying editable smart filters
      6m 8s
    10. Combining two smart filters
      8m 5s
    11. Assigning a filter mask
      5m 59s
    12. Nesting one smart object inside another
      10m 32s
    13. Employing a static High Pass layer
      8m 59s
    14. Matching static pixel-level edits
      4m 37s
    15. Avoiding clipping with luminance blending
      9m 7s
    16. Sharpening and smoothing
      6m 36s
    17. Making an edge mask
      8m 14s
    18. Making a non-edge mask
      7m 17s
  5. 1h 33m
    1. Sharpening with Adobe Camera Raw
      1m 29s
    2. Introducing Camera Raw (4.1 or later)
      8m 13s
    3. Understanding why to sharpen for source
      5m 14s
    4. Using Camera Raw’s sharpening control
      5m 52s
    5. Previewing limitations and tricks
      6m 45s
    6. Why downsampling doesn’t work
      3m 12s
    7. Reducing chromatic aberration
      7m 30s
    8. Using the Defringe option
      3m 32s
    9. Understanding high frequency, low radius
      5m 21s
    10. Raising the Detail value
      3m 6s
    11. Using on-the-fly edge masking
      5m 41s
    12. Sharpening a low-frequency portrait
      6m 36s
    13. Eliminating color noise
      4m 47s
    14. Reducing luminance noise
      4m 42s
    15. Correcting “false sharpening”
      7m 15s
    16. Reducing shadow noise
      5m 22s
    17. Approximating ACR sharpening in Photoshop
      8m 35s
  6. 59m 8s
    1. Gauging and exploiting luminance frequency
      1m 27s
    2. Using low-frequency source sharpening
      5m 53s
    3. Using High Pass for portraits
      4m 19s
    4. Actioning a low-frequency edge mask
      7m 42s
    5. Modifying the source sharpening
      5m 21s
    6. Using high-frequency source sharpening
      5m 26s
    7. Using Smart Sharpen for cityscapes
      3m 2s
    8. Actioning a high-frequency edge mask
      5m 4s
    9. Downplaying color artifacts and clipping
      4m 4s
    10. Sharpening a medium-frequency image
      5m 24s
    11. Sharpening a layered composition
      7m 16s
    12. Sharpening for multiple frequencies
      4m 10s
  7. 1h 8m
    1. Who needs dull when you have sharp?
      56s
    2. Focusing in on a person’s eyes
      4m 22s
    3. Blurring the area outside the eyes
      4m 22s
    4. Sharpening eyes and other details
      5m 38s
    5. Darkening the lashes and eyebrows
      7m 13s
    6. Sharpening dark-haired people
      5m 2s
    7. Edge mask and emphasize
      3m 39s
    8. Nesting a Smart Sharpen effect
      4m 48s
    9. Density mask sharpening
      5m 35s
    10. Adding depth of field
      4m 39s
    11. Sharpening a background
      4m 23s
    12. Masking background from foreground
      8m 51s
    13. Eliminating halos around a person
      5m 38s
    14. Deepening and warming a background
      3m 28s
  8. 1h 18m
    1. Reverting back to convention
      1m 37s
    2. Understanding the use-neutral composition
      4m 15s
    3. Restoring much-needed antialiasing
      4m 2s
    4. Reducing noise in a high-frequency image
      7m 24s
    5. Making a third-level smart object
      3m 55s
    6. Preparing an image for print
      5m 18s
    7. Using ideal settings for commercial reproduction
      5m 37s
    8. Calculating very large-format settings
      5m 11s
    9. Using ideal settings for inkjet output
      4m 26s
    10. Sharpening for commercial reproduction
      5m 45s
    11. Sharpening for inkjet output
      4m 58s
    12. Revealing high-frequency multipass sharpening
      5m 21s
    13. Using Gaussian Blur to sharpen hair
      5m 41s
    14. Flatten, Save As, Resample, and Sharpen
      5m 9s
    15. Revealing low-frequency multipass sharpening
      3m 30s
    16. Sharpening an image for web or screen
      6m 22s
  9. 1m 50s
    1. Goodbye
      1m 50s

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