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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