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Alright gang, are you ready to build your own Unsharp Mask using nothing more than Gaussian Blur, Apply Image and a booey knife? In this exercise we're going to see how. Now I do want to stress right upfront that there is no earthly reason to do this, this is not a technique, I am not suggesting that you do this on a regular basis for your own images. You'll see this is a very complicated technique that I am about to share with you and you would not want to do this on a regular basis. Even if you actioned it, you'd be out of your mind to work this way. The Unsharp Mask ommand is much more convenient. I am just showing you this so that you have a sense of how Unsharp Mask works and how it is that Photoshop uses blurring in order to create the effect of sharpening because after all, Photoshop is utterly incapable of generating actual detail inside of an image, so instead its just an illusion.
So here I am working inside this Test shapes.PSD image, which features this Background layer, this demo file here. The Background layer with this USM 100/12/0 layer sitting on top of it that we'll use to compare the two effects once we are done. I am going to turn that layer back off, I've got the Background layer selected, and now I don't necessarily expect you to follow along with me, I am going to work fairly quickly through this because its not necessarily going to make a ton of sense, but I just want you to see this is how it works. So I am going to start by pressing Ctrl+Alt+J or Command+Option+J on the Mac in order to jump this image to new layer, and I am going to call this layer Gblur 12.
It's going to be Gaussian Blur with Radius of 12 pixels. I am going to click OK, then true to it's name, I am going to go up to Filter menu, I am going to choose the Blur command and I am going to choose Gaussian Blur. It's probably still set to that big whopping a 140 pixel value. I am going to change it to 12 pixels and I am going to click OK. Now believe it or not, this is going to create the effect of height and contrast. I know its hard to believe but it is going to do it. That is the only filter we're going to be applying is Gaussian Blur 12 right there. The next step is to go back to my Background layer, grab the original version of the image, and I am going to jump it once again by pressing Ctrl+Alt+J or Command+Option+J on the Mac, and I am going to call this layer, this may seem crazy, but I am going to call it Orig minus Gblur, because we're going to actually take the original version of the image and subtract the Gaussian Blur version of the image from it.
So I'll click OK and then I'll take this guy and I'll drag it on top of Gaussian Blur. So we reinstate the original version of the image. Now I am going subtract the Gaussian Blur version of the image using the Apply Image command. So I'll go up to the Image menu and I'll choose Apply image and I will go ahead and set Layer, currently we're applying whatever it is we are applying. We're applying it to the Original minus Gblur layer right here. The layer that I am going to apply to it is Gblur 12, and then I am going to set the Blend mode to Subtract, in order to subtract that image, the Gblur image, from the original image, and I am going to leave Scale and Offset set to their defaults.
So 1 and 0, notice that Opacity is set to a 100%, that's all I am going to do. I'm not going to Invert anything. I am going to click OK in order to accept that result. Now this may look crazy but you can see what we have is we have the highlight edges set against blackness. So now lets mix these guys together. I am going back to the Background image, I am going to jump it once again by pressing Ctrl+Alt+J or Command+Option+J on the Mac, and I am going to call this one Orig+(0-GB) and then click OK.
So basically I am going to take this guy and add this guy to it. Let's go ahead and move it to the top of the stack so we can see what we were doing, and I'll go back to the Apply Image command under the Image menu and I am going to set the layer this time to this one, Orig minus Gblur, and instead of subtracting I am going to go ahead and Add it, and watch this. We get the highlight edges right there. Isn't that cool? Check it out, I think that's awesome. These are highlight enforcers, the highlight enhancements that are associated with Unsharp Mask.
Then I'll go ahead and click OK. Now we still need the dark edge in here. We need the shadow edge, and so we're going to have to build that manually as well. So I am going to go down here to the Background layer. Once again, go ahead and Ctrl+Alt+J, Command+Option+J to jump it. This time I am going to call this one O, for Original, plus GBinv, which is Gaussian Blur Inverted (O+GBinv). So this time we are adding by the way and still subtracting, and I could actually spell it out because last time I spelt out minus for this letter.
So I'll spell it out O plus GBinv, click OK, drag it to the top of the stack, go up here to the Image menu, choose the Apply Image command, so a pretty familiar stuff, even though its mind-boggling at this point but still familiar. I am going to go to Layer and I am going to set this guy to Gaussian Blur 12 once again and instead of subtracting it, we're going to go ahead and add it, but we need to add an inverted version of this. It's way too highlighted, it's like we've got back-lightning going on. I am going to go ahead and click on the Invert option in order to create this effect here.
So we are getting rid of this white zone and we're going to keep the shadow edges. Now click OK in order to accept that effect. Now I am going to go back to Orig+(O-GB), that layer, the one that has, if I go and turn this layer Off for a moment, you can see this is the layer that has the highlights applied to it. So I want it to be selected, I'll go ahead and turn on again 0 plus GBinv. I am going to jump that layer by pressing Ctrl+Alt+J or Command+Option+J on the Mac, and I am to call this one Orig+(0-GB) just like we have, and then minus the sum, which is (0+GBinv) for invert.
It's not necessary that you name these layers anything; you don't have to name them so scrupulously as I am doing, I am just doing so that I can keep track of what the heck I am ought to. I'll click OK, drag the guy to the top of the stack so that you can see it. We are actually going to subtract away those dark edges by going up to the Image menu, choosing the Apply Image command and we're going to go ahead and set the layer to this guy right there, 0 plus GBinv and were going to subtract it this time around by changing the Blend mode to Subtract and look at those dark edges.
So we have the highlighted edges, we have the shadow edges, everything's there, I'll go ahead and click OK in order to accept that modification. Now I am going to zoom-in because some of you might be thinking by this point, if you are thinking at all, if you have any semblance of a brain left, you might be thinking this can't possibly be the exact same effect. Now I am going to scroll to the top of the Layers palette, I am going to turn on USM 100/12/0. That is an authentic application of the Unsharp Mask command. Did you see anything change? Nothing changed. That's because we exactly emulated, this is not even simulation.
It's an exact emulation of Unsharp Mask set to a 100 with a Radius value of 12 and a Threshold of 0. You can build your own Unsharp Mask command using nothing more than Gaussian Blur and Apply Image. So this is totally the effect of sharpening created using blurring. Now at this point you might say, "Wow! that's really cool, Deke, where in the world did you learn that one?'" If you are thinking it's cool of course. And the truth of the matter is, I came up with it myself. Alright, you should just kNow I mean that's the kind of sick man I am.
In the next exercise we will be shifting focus away from this totally theoretical, ridiculous application of the Gaussian Blur function, we will be shifting to a much more practical application of the Smart Sharpen filter in Photoshop CS3.
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