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In this exercise I'm going to introduce you to really a great sharpening function that has a really crazy name, and that's Unsharp Mask. Now I'm still working inside Orange on blue.jpg found inside of the 14_sharpen folder, and I want you to go up to the Filter menu, choose Sharpen, and there is Unsharp Mask. Now notice, if you loaded my Deke Keys, way back near the beginning of the previous part of the series Photoshop CS4 One-on-One Fundamentals, then you have access to a handful of keyboard shortcuts for the best of the filters.
So I have got Shift+F5 for Unsharp Mark, Shift+F6 for Smart Sharpen, on and on all the way up to this guy right here Shift+F10 for High Pass, which itself is a sharpening function. Now I should say before I go any farther, that you can learn more about sharpening. If you start getting into this, and you find it to be interesting, and it really is important stuff, especially if you do a lot of output work, meaning you print a lot of your photographs, you really want to know the ins and outs of sharpening. I had explained how sharpening works in glorious detail, all kinds of different sharpening scenarios for output, for effect, for detail, and for acquisition too, for input, inside of my series Photoshop CS3 Sharpening Images. Sharpening technology really hasn't change here inside CS4, so all the information inside the CS3 Sharpening images series is accurate, except for the part where I rail against the screen resolution or the zoom ratios, and that has actually been resolved in Photoshop CS4, and I'll explain that more in detail as we get into it. But I just want you to know, there's a whole series about sharpening there available to you in the lynda.com Online Training Library, so check it out at your leisure.
Unsharp Mask, it also tells you why Unsharp Mask is called Unsharp Mask. It's based on an old traditional camera technique, and the idea is that you are using blurring, because you can't really sharpen something imposed, it's really pretty much impossible. You can't blur detail imposed, and so Unsharp Mask uses blurring and actually blurs the edges and then masks them in order to create the appearance of sharpening. Is that not weird? And in fact, down to the last pixel, you can mimic the effects of Unsharp Mask using just Gaussian Blur if you want to. True story and I'll show you how to do it, if you want to geek out inside that sharpening images series I was telling you about.
But for now, I just want you to know, it's got a crazy name but it's a great function. It is the Premiere Sharpening function inside a Photoshop, and then it got updated for Smart Sharpen. All right, so I'll go ahead and show you this command, here it is, brings up a dialog box. Let's go ahead and zoom out, a click for the snake for the in dialog box preview. You also have an out of dialog box preview, so you'll see the image change on the fly as long as the preview check box is turned-on. Now in the old days you really had to watch your zoom ratios, when I say old days, I mean Photoshop CS3 and earlier. You had to watch your zoom ratio, something like 67% would be bad, it would be just dropping pixels, and you wouldn't really be able to accurately gage the sharpness of the image.
Now, assuming that you have an OpenGL compliant video card inside Photoshop CS4, you are going to be able to gage good sharpness at pretty much any zoom ratio, and definitely the standard ones are just fine. So these ones that you get by clicking the minus and plus buttons work out beautifully. And I'll show you how to make sure you have got an open OpenGL compliant card in just a couple of exercises here, when I show you how to measure screen resolution. But in the mean time, let's discuss Unsharp Mask, it has three sliders, and at first they are little daunting, but once you learn how to used them, it all make sense, really easy to use this command.
The first one I think is really easy right out the gate. It's just the amount. How much sharpness do you want to apply? Wouldn't it be great for new people if they just made a command instead of having sharpen that just has, you know, the static group of these three options that it applies? Wouldn't it be great if you had sharpened dot-dot-dot, and all it gave you is amount? At least you could control the amount of sharpness and then the newbies would be satisfied, it'd be awesome. But we don't have anything like that, but you could just apply this amount, and notice, if I apply a higher amount value, I get more sharpness on screen.
Great, that's too much sharpness. I'm over sharpening the image, but still, you know I can gauge the difference here, and I can go as high as 500%. That just controls how much sharpness you want. Then let's go ahead and crank it up actually, I'll set it to 250, so we can really see what we are doing. Radius, defines the thickness of the halos. Now it's telling you Unsharp Mask is using a blurring technology in order to create the appearance of sharpness, and I was also telling you in the previous exercise, it's enhancing the contrast around the edges, right? So it's making the dark edge darker, and the light edge lighter. So look at the snout up here.
See how you can see a little bit of dark edge at the top? I'll go and zoom in, and I'm doing this by the way by Control+Spacebar+Clicking. That will be Command+Spacebar clicking on the Mac. So you can't zoom even though you've got a dialog box opened. Now you can't zoom by pressing the Z key, as you can't when the dialog box is close, but you can use that old technique of Ctrl+Spacebar or Command+Spacebar+ Clicking, and you can also just press Ctrl+Plus or Ctrl+Minus, Command+ Plus or Command+Minus on the Mac. All right, so see that little edge there, little dark edge above the snout, light edge below the snout. Watch it gets thicker as I change the radius value.
So notice there is more of a pop now, more of a blur, bigger halo expanding outward and expanding inward. So if you go with high radius value, you can get big thick goopy edges like we are seeing here, and if you go with a low radius value, you are going to get a nice crisp exacting edges, which would make you think you always want a low radius value, but I'll tell you why that's not true in future exercises here. Anyway, let's change this to radius of 2, and then we have this threshold value. Now edges are areas of rapid contrast between neighboring pixels. You've got basically 2 pixels that are right next to each other, let's say, anywhere in the image. Threshold value is saying, all right, if there are at least 0 luminance level different from each other, I'll sharpen them. So in other words, it's going to sharpen everybody inside this image, because everybody is at least 0 levels different than each other.
However, if you've raised that value to let's say 20, okay, then it's only going to sharpen 2 neighboring pixels where they are at least 20 luminance level different from each other, bearing in mind of course, that there are a total of 256 luminance levels in an 8 bit per channel image, and even if you are working in a 16 bit per channel image, threshold is just imagining you're working with 256 levels. You can only go as high as 255 levels there of difference and that, of course, is going to illuminate all sharpness from the image, because no two pixels can be 255 different from each other, unless they are white and black. I guess might be, but I'm not seeing any neighboring pixels that are white and black. Then if you sharpen them, you couldn't create more contrast between them, then black and white, so anyway, no sharpening occurs.
The problem with this function here, and the reason I don't use it, I actually don't use it at all, some people use it sparingly, and I'll tell you how to do that. But if you take it up to something like 30 levels, notice you get this pock marking effect, and that's because it's an on/off proposition, either you are sharpening 2 neighboring pixels, because they are at least 30 luminance levels different from each other, or you are not, because they aren't, and as a result you get this weird, the sun sharpness inside the image, and it usually does a really great job of picking out bad detail like pock marks, and moles and zits. And it's horrible.
However, if you keep it low, you can get half way decent effects, something like 3 to 4 for a low-noise image, this is a pretty high-noise image, so threshold value of about 8 level works pretty nicely for avoiding sharpening the noise in the background, behind the snake there. But we still are getting that pockmark effect, that on/off propositions, so we are drawing at some details and not others, which is why my favorite threshold setting is 0. Anyway, that gives you a sense. There is your three sliders. In the next exercise, I hope to help you make you sense of the most mysterious and the most important of these three sliders, the radius value, coming right up.
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