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There's nothing people love more than lists, and Photoshop Top 40 offers a great one, highlighting the best features in Photoshop. Deke McClelland counts down to #1 with a new video each week, detailing one great feature after another in this popular digital imaging application. The videos cover tools, commands, and concepts, emphasizing what's really important in Photoshop.
This is an ongoing course that will be updated monthly.
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(Music playing) Deke's Photoshop? Deke's Photoshop? Top 40! Feature #14 is Gaussian Blur and what the Gaussian Blur filter does is it blurs an image according to a Radius value. It's an extremely simple filter as we are about to see. I am working inside this image from photographer Coka and I am going to take this layer right here that's called O for original and I am going to press Ctrl+Alt+J or Command+Option+J to jump it. And I will call this new layer GB (4), because I am going to apply the Gaussian Blur filter with a radius of 4 pixels, click OK. And then I am going to go up to the Filter menu, choose Blur and choose Gaussian Blur. That's my keyboard shortcut right there that I assigned. And that brings up this very simple dialog box. I will click on the eye so that we can see I have got a Radius value of 4 pixels so that we are distributing the blurriness in circles that have a radius of 4 pixels. So we are talking about a circle with a diameter of more than 8 pixels actually because of the way Gaussian Blur works. But what ends up happening here, as you can see, this is before, inside the dialog box, nice crisp eye, and this is after, and it's now quite blurry. I will click OK. How in the world is this a useful effect? Forget about the fact it's on the Top 40 list that I put it actually above, more important than feature #15 alpha Channels, how is it useful at all? Well, the reason that Gaussian Blur is so great and I will show you a use for it as well. But the reason it's so great is that the Gaussian method of distributing luminance levels or translucency levels or what have you inside of Photoshop is that work throughout the program. Anytime you see a Size value when you are applying Drop Shadows or Glows or any of those functions, then you are experiencing a Gaussian Blur as well. And let me show you here. I will switch to this image. Its Shadow demo.psd file. We were way zoomed in, so that you can see the pixel grid. I am going to press Ctrl+H, Command+H on the Mac to hide that grid. Now imagine we are looking at a Drop Shadow here. We have a rectangle that's casting a black shadow on to a white background. Worry not for blur. Some form of blur inside of Photoshop, then we would have this hard edge shadow right there which wouldn't look naturalistic at all. Now if we did a Standard blur, as occurs inside of some other programs, I am going to bring up my Layer Comps palette, feature #39 you may recall. And I am going to switch to Linear Blur, and Linear Blur is very popular in lesser programs. They were very popular inside of the programs that basically Photoshop destroyed. So back when there are used to be a lot of image editors and painting programs, a lot of them used Linear Blurs. And the thing about a Linear Blur is that each level of translucency or each luminance level or what have you is given the same amount of weight. So we are stair-stepping from one level of translucency to another here. And that's all very well and good until we get to the edge, and then we have a sudden drop off from where the Drop Shadows ends and where the background begins, and we can see that edge. We have a harsh edge to our soft shadow. And that doesn't even make any sense. We can even see the corner up here if you look very closely and were you to print this image even at a very high resolution. It's very possible you would see that edge. Whereas if I switch to Gaussian Blur, you can see that we have a much smoother distribution here. And ultimately you can't see the edge of that blur. It just fades nicely away. And how this happens by the way? What Gaussian blur does is it blurs very slowly at the beginning of the blur, then it blurs rapidly in the middle and then it drops off at the end and blurs very, very slowly again, so that we have a truly soft effect. Now I am gong to switch back to this image from Coka, and what I want to show you here is that Gaussian Blur is at work not only for Drop Shadows and Glows and the other layer effects, but it's also at work for sharpening inside an image. So whenever you are sharpening an image inside the Photoshop, you are actually trapping blurs. And let me show you how that's put together. Now what I am going to show you is not anything that I intend for you to use ever. It's not a technique. It's not something that I really expect you to understand. I just want you to see that this is what Photoshop is doing in the background. It is blurring an image to sharpen it. So we will start with this GB (4) image right here and then on top you can see that I have created a bunch of different layers, all of which are copies of O. That is Original. And one of them is called X: O-GB, and they have these little equations that we are going to be employing right here. I will go ahead and show this layer, this X layer and select it, and then I am going to go up to the Image menu, I am going to choose Apply Image. This is the original version of the image, bear in mind. And I am going to take the Gaussian Blur version of the image right here. I am not going to invert it, so I will turn that off. But I do want to subtract it. So I am taking the Original minus Gaussian Blur. That's what I have done. Thanks to Subtract right there. And I will click OK. Now that looks like nothing, right? It looks like I have turned the entire image black, but if you look very closely you will see these minor highlights that are showing up. We will put those to use in a moment. Now I am going to click on the Y layer, turn it on. Go up to the Image menu, and choose Apply Image again. And this time I am going to follow this math. So I want to take the original, add Gaussian blur and Invert. So once again, I have got Gaussian Blur selected. I will switch to the Add mode and I will turn on the Invert checkbox and we get this effect here. Mostly white with a few shadows here and there, click OK and then finally we are going to put everything together. I am going to take O+X-Yi. So I am going to have to apply two passes of the Apply Image command. Go up to the Image menu, choose Apply Image, then I will switch my layer to the X layer right there and I want to Add it. You would see O+X, however I do not want to Invert. So I will turn that off. And we have now a few light highlights going around these eyelashes. So this is the before version of the image, this is the after version of the image. So we have applied some sharpened highlights. I will click OK. Now to add the sharpened shadows, I will go right back to the Image menu, choose Apply Image once again. This time I want to do a subtraction of Yi. So I will switch to the Y layer. I will make sure that I am subtracting it and I will go ahead and turn on Invert. And we end up getting sharper shadows and to prove that's true, I will go ahead and turn off the Preview checkbox and then turn it back on. And you can see that those shadows are now sharper. I will click OK. And let's zoom in on that eye right there and you can see how sharp it is. This is the original version of the image, before I sharpened it using only Gaussian Blur. Notice no other filters were applied. Just Gaussian Blur and the Apply Image command, and this is the sharpened version of the image. And just to give you a sense of how identical this is to the Unsharp Mask command, I will Alt+Click or Option+Click once again on the eyeball in front of O, so we are only seeing that O layer. I am going to click on it, so it's active. I am going to go up to the Filter menu, choose Sharpen, and choose Unsharp Mask. An Amount value of 100%, that's very important for matching the Gaussian Blur effect. Then Radius is 4 pixels. That exact same Radius value that I applied with Gaussian Blur. It is Gaussian Blur. That is Gaussian Blur built in to the Unsharp Mask dialog box. I will click OK in order to apply it, and now note the difference between these two. This is the image that we sharpened with Gaussian Blur. I just turn it on. This is the image sharpened with Unsharp Mask, the exact same effect. Now so far all this is very interesting. I just want you to see that Gaussian Blur is that stream that's running throughout Photoshop. So you are encountering Gaussian Blur even when you don't know you are using it. But there are also ways to actually employ the command. So I am going to switch to this image, and it comes to us from Photographer Lucian Coman, also of Fotolia. And what I would like to do is smooth over some of the imperfections inside this guy's skin and I will do that by applying a kind of layer of digital make up, essentially using Gaussian Blur. So this is a quick and dirty effect essentially. I will start things off by converting this guy to a Smart Object, feature #18 of course. And I will go up to the Layers palette fly-out menu and I will choose Convert to Smart Object. That of course protects the pixels inside the image. Now I will go ahead and rename this guy dude or something along those lines. Now to go to the Filter menu, choose Blur and choose Gaussian Blur. And I am going to up the Radius value to 20 pixels. So I am just blurring the heck out of this guy at this point, click OK in order to accept that effect. Photoshop goes ahead and applies Gaussian Blur as a nondestructive, modifiable Smart Filter. Now I need to change the blend mode assigned to the effect, so I will double-click on this little slider icon to bring up the Blending Options dialog box and I will switch the mode from Normal to Overlay. And this is a heck of a great effect, by the way, but it does tend to result in too much contrast. So we're blowing a few highlights, we're definitely filling in shadows, and we've got too much saturation inside the image. That's okay. Leave it along. Click OK in order to accept that effect. And now what we're going to do is we're going to lower th contrast of the original image here inside the Smart Object. So I'll double-click on the thumbnail associate with the dude. Then I get this alert message telling me that I'm going to modify the contents of the Smart Object. So click okay to say, sure enough. That's what I want to do. Soon this guy in a couple of clicks they'll go out to the arranged document sign time here in the PC and all switch over to too a lot so that I can see both the smart object and the larger composition at the same time and under press shift and spacebar and drag so they can scroll both of these images at the same time. And now we want to do is we want to reduce the contrast of this hello so that the contrast of the Gaussian blur image matches so that we have the same colors in the same contrast warmer done for him to do that use seeing the curves command. You may recall feature number 24 applied as an adjustment layer feature number 16 song you go to the adjustments palette in and in the click on curse) or to add a curves adjustment layer and then on to add three points to this graph one of which is going to be right about here and input die EU of 20 and an output value of 45 and these are not magic numbers by the way the East just happened to be number set work well for this image and then on to set another point at an input level on 75 and an output of a hundred right there. And then finally I'm good at a point toward the top and this time I won an input lowball of 210 and in output level of 200. So he ends up looking quite low contrast inside of the Smart object spread outside once we update the smart object is, look great and to update the smart. Object O go to the file menu and choose the save command essays the changes made to the smart object to the larger composition as we can see right there and to just confirm that we have the same locals of contrast to work all turn out the curves layer for a moment. There's the original contrast to the image there's a new contrast, and they both match each other and what's wonderful about this is we now have a soft blur of fact it's applied to the image we can still see the underlying detail just fine for the details not quite as aggressive as it was before thanks to Gaussian blur combined along with the overlay blend mode, and that's just one example, what Gaussian blur can do it for that command that you can use if you want to directly on an image for each and use in a variety of different forms in the background Gaussian blur. It really does set Photoshop apart.
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