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In the last movie you saw me selectively sharpen this image by duplicating the Background layer, Sharpening it, and then adding a layer Mask that hid the layer entirely. I then took a white paintbrush and painted into that mask to reveal only the areas of the sharpened layer that I wanted to be able to see, and that let me selectively sharpened the eyes and the hair. We are going to do the same thing in this movie, but I'm going to use a different method to create the mask, rather than going in and having to paint it by hand. I'm going have Photoshop create a mask for me.
There are lot of filters and image editing operations in Photoshop that allow you to create kind of weird special effects kind of looks, and one of those filters is a filter called Find Edges. I'm going delete this sharpened layer here. And let's go up here to Filter > Stylize > Find Edges and what that does is it goes through my image and finds only edges and exaggerates those and gives me this weird looking affect, which actually does me no good at all in terms of creating a final image.
But if I think about Selective Sharpening, what I want to do when I selectively sharpen is to sharpen only the edges in an image. And with the technique we saw in the last chapter, we saw that I could sharpen an image and then create a mask that revealed only areas that needed to be sharpened. Well, here I've got a Filter that will automatically find edges in the image, so if there's a way that I could use this to build a mask, then I could have Photoshop automatically find edges, use those find edges as a mask and then apply Sharpening through that mask and so I'd be sharpening only edges, not surface features, like skin texture.
So that's what we're going to do here and the way we're going do it is we're going dive into the Channels palette. As you know, or as you should know I hope, color in an image is created by mixing red, green, and blue, and in Photoshop those separate red, green, and blue components are stored as Channels. And I can look at individual channels. Here's all the Red information in the image, here's all the Green, here's all of the Blue. If you're wondering why they are Grayscale, it's very simple, these images are showing your density of each specific color. So I'm looking at a map of the density of Blue in the image, where there is Black, there is no blue, where there is White, there is Blue, where there is Gray, there is something in between, same thing here for Green, same thing here for Red.
If you think about skin tones, skin tones have a lot of red in them, so that makes sense that the Red channel would be very white on her skin because there's a lot of red there. It also makes sense that the Blue channel would be very dark, because there's not much blue there. Her teeth are light in all three images, because white is an equal mix of red, green, blue, same with the whites of her eyes. So none of that's really necessary to understand for the sake of what we're going to now. All I want to do is look through these three channels and find the one that has the most useful edge information in it.
I'm watching her eyes and while I can see good definition in her eyelashes and eyebrows, in the Blue channel I see also all of this skin texture, and of course, all of the skin texture on her face. Same with the Green channel, but in the Red channel her face is mostly blank, it's mostly white and all I see are eyelashes and eyes and good hair detail. I can see the lines that define the edge of her face. So this is a good starting point for trying to get an image that's distilled down to only edges.
So what I'm going to do is duplicate my Red channel, because now I'm going to mess with it. This channel is just a normal grayscale image I can do anything that I want to it, so I am going to go up to Filter and go to Stylize and choose my Find Edges, and when I do that, I get this. Now Masks of course are simply black and white. Black areas are masked, white edges are not, so this is already starting to look a little more like a usable mask. I'm going to bring up my Levels dialog box now and increase the contrast. I want to really bring out the hard edges that I what to lose some of that skin texture.
So I want to see if I get this down to just looking like I'm only seeing lines that are relevant to edges that I might want to sharpen. Now that's looking pretty good. I am seeing a lot of good stuff here under eyes. I am going to do a little bit of sharpening on the edge of her teeth, on her necklace, lots of sharpening on her hair, I am going to hit OK there. Now the problem is black areas in a mask are masked, they are protected. In other words, sharpening is not going to go through to these black areas, it's going to go through to the white areas, which are all her skin tone. So what I need to do is invert this layer.
If I go to Image > Adjustments > Invert, now I get the negative version of it. This is looking really good. If you remember the last tutorial, I painted white into the mask in the areas that I wanted to sharpen. This is looking like kind of stuff that I might paint, but with the Level of Detail, that I'd never do by hand, and probably could not do by hand. So now what I need to do is load this as a selection. If I pick up this channel and drop it on this little Load Selection icon down here at the bottom of the layers palette, I can see my marching ants stuff around here.
So I now got a selection, I'm going to click on RGB to go back to my Normal view, and go back to my layers palette. Now I'm going to duplicate my Background layer, because again, I want to keep my sharpening discreet, I want to be able to throw it out later if I want. I'd also like to get rid of these marching ants, they're annoying. I could do Command+H, or Ctrl+H, or I can go up here and turn off Shows Selection Edges. My selection is still there, it is just I don't see all of that stuff on the screen. Filter > Sharpen > Smart Sharpen just like we did before, and just as we did before, I am going to zoom in here to 100%, taking my Default values to start with.
I'm going to turn off Preview, and I'm watching her eyes as I turn it on and off, and I'm seeing a difference. Her eyes are sharpening, so are her eyebrows. I am not getting any change on her skin texture. The sharpening is not quite as aggressive as the same settings were previously, and I think that's because the mask is filtering some of the sharpening effect. I am going to launch her hair over here, as I turn that off. I'm picking up some sharpening on her hair. I am going to turn up the Amount just a little bit to get a slightly more aggressive sharpening, and I think that's a little too much, since the mask seems to be filtering some of it out, and I think that's looking pretty good.
I'm going to say OK and zoom out and just see even from this distance if I can tell, there are some differences overall. So I don't see the mask that I've created, it's just applied directly to the sharpening. I could actually apply this as an Adjustment layer, but there's really no need if I don't like the Sharpening, I'm just going to delete the layer and start over. So, edge masking of this type is a way of getting very complicated edge masks built, so that you can again constrain your sharpening just too some areas in your image.
Honestly I don't use this as often as I use the technique we saw in the last movie. But for times where I have got a really noisy image, I want to be really careful about protecting skin tone or for times where there's lots of fine detail throughout the image that I'd like to have sharpened, this is a great technique. In this case since it's really just her eyes, that's an easy enough thing to paint, but in the landscape image or maybe I have got foliage all throughout the image that I want to selectively sharpen, this is a very easy way to do it.
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