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The elusive alpha channel remains one of the most misunderstood yet powerful tools in Photoshop. Alpha channels are collections of luminance data that control the transparency of an image, and they inform just about every aspect of Photoshop. As he builds transitional blended layers, fashions a depth map, makes edge adjustments, and takes on extreme channel mixing, Omni Award-winning expert Deke McClelland teaches Photoshop users that where there's a will, there's a way. Photoshop CS3 Channels and Masks: Advanced Techniques covers mapping texture on an image, turning flesh into stone, using vector masks, working with all different channels, creating a rustic edge effect, and much more. Exercise files accompany the tutorials.
Download Deke's customized keyboard layouts for Channels and Masks from the Exercise Files tab."
For our next project, we are going to take the same composition that we have been working on so far and we are going to sharpen the focus of the image using a combination of a High Pass layer a Density Mask and this is taking the high road basically. We are sharpening like professionals at this point rather than just uniformly sharpening the image across the board which is a dangerous thing to do with a portrait shot. We are going to just focus in on the best details inside of an image and that takes a little bit of finesse as you are going to see. Let's see how we would do things just sort of the regular way, the standard way to sharpen inside Photoshop. I am going to zoom in on this image considerably so that we can see the image at the 100% zoom ratio which is the best way to judge sharpening and I am working by the way inside of an image called The final color mask.psd.
It's found inside the 12 Specialty folder and it's called The final color mask because it does indeed exhibit the final version of the color mask in which we changed her blouse from crimson to yellow. Go ahead and select the Background layer because that's the layer that we want to sharpen. We can't really actually apply a sharpening filter to the Hue/Saturation adjustment layer. Then let's just work with static controls at this point. I am not going to bother with Smart Objects and Smart Filters. Go ahead and choose from the Filter menu, choose the Sharpen command and then choose this guy right here, Smart Sharpen and I have given you a keyboard shortcut. It is a very important command. If you loaded my Deke Keys shortcuts back in the preface then you can press Shift+F6 in order to invoke Smart Sharpen.
Basically the Smart Sharpen function includes everything that you can do with Unsharp Mask and then some. So it really is your when in doubt sharpening function inside Photoshop CS3. I am going to go ahead and choose the Smart Sharpen command and by default you will probably see some values along these lines. You will see the Amount value set to 100%, Radius of 1 and Remove set to Gaussian Blur. We are working with a digital photograph so we want to set the Remove function to Lens Blur which is going to account for any blur that's associated with the photographic process. So go ahead and choose the Lens Blur option and then I am going to suggest we take the Amount value up to 250%, so we have a lot of sharpening and I am going to take the Radius value up to 3 pixels. So we get some pretty thick edges.
So basically the idea where sharpening filters are concerned inside Photoshop is the program is going through and evaluating the edges inside of the image and edges are any point at which there are radical transitions between two neighboring pixels. So it locates these edges then it exaggerates the degree of contrast between these edges. So it takes already radical transitions and makes them even more radical. And so if it encounters sort of a light gray pixel next to a dark gray pixel, it might change the light gray pixel to white and the dark gray pixel to black.
That's how radical we are going here and then the thickness of those exaggerated outlines that it draws around the edges is determined by this Radius value right here. So you can see at this point that we have a fairly well sharpened image. I will go ahead and match the interior preview to the exterior preview there. The problem is that we are not only focusing in on the good details inside the image such as the eyes and the eyebrows and the under side of the nose and so forth, but we are also sharpening her pores and her moles and you know all that stuff as well. Stuff that we might not want to sharpen inside the image and I don't think we do inside of this portrait shot.
Generally you don't and by the way, see this More Accurate check box right there. Leave it off when you are working with portraits, definitely a dangerous check box. I will go ahead and turn it on so you can see. Basically it riddles the image with further sharpening; sort of a micro sharpening that digs deep into those pores. You don't want that for a portrait shot, so leave that turned off. If you were going with the Smart Sharpen function, these would be some good settings to work with. I am going to suggest that we can do a better job with a High Pass layer. So let's go ahead and cancel out of there and we will return to the comparatively fuzzy image.
Now what I would love to be able to do inside of Photoshop CS3 is convert this background into a smart object and then apply High Pass which you will see is really great for sharpening. Apply High Pass as a smart filter which is possible to do. The problem is then you don't have the control over that High Pass layer that you need to have. So we have to do this the old fashioned way that is the Photoshop CS2 and earlier way, not -- without the aid of the smart filter and I will explain why that is when we come to that juncture. Anyway, go ahead and make sure you still have the background layer active inside of this composition, then I want you to press Ctrl+Alt+J or Command+Option+J on the Mac in order to jump to layer and display the dialog box. I am going to call this new layer sharpen and it's just a copy of the background layer.
I will click OK and one of the reasons I would prefer, I should say this the reason I would prefer to work with a smart filter combined with a smart object is because that way we wouldn't to have to create a duplicate of the image. When you duplicate the image you grow the image size and you can see it down here in the bottom left corner of the Image window. It says, Doc: 18.3M. Now for me the layer version of the image just jumped up to 38.9 M. So we just basically doubled the size of the image. Smart filters don't do that. Anyway though, it's not an option. We can't use the smart filter for the reasons I will show you as I say. Now I am going to move this image to the top of the stack by pressing Ctrl+] or Command+] on the Mac and what that means, if I zoom out here you can see that I have reinstated her crimson blouse. Here it is without the sharpened layer, here is the image with the sharpened layer.
So I have undone all that work we did over the course of last few exercises. That's actually okay. We are going to come right back to it in just a moment. As soon as we blend the High Pass layer with everything below, all that crimson will drop away. So here is what you do with High Pass. This isn't going to seem like a sharpening effect at all. I am going to zoom back in on the image incidentally. I am going to go up to the Filter menu, choose Other and I am going to choose the High Pass command and notice that I have given you a keyboard shortcut for this one as well because it's so ultra useful, Shift+F10. Once again if you loaded my Deke keys way back in the preface and what it does though, doesn't seem like an appealing thing to do at all. It goes ahead and turns the image gray.
So the idea is higher Radius values ironically in this twisted world of High Pass, higher Radius values seem to do less to the image, they appear to do less to the image. Whereas lower Radius values wreak more of this gray havoc on the image. I want you to take this value up to 3 pixels. It is a Radius value. It's just like that Radius value inside the Smart Sharpen dialog box. It defines the thickness of the edges. So imagine this. Imagine we are sending the image through a funnel and every color that goes through the funnel drops away to gray but then the edges are hanging on for dear life and they are refusing to go down the funnel. So all the non-edges turn gray and the edges turn gray to lesser extents based on this Radius value.
So with a tiny Radius value like 3 pixels relatively small we get just a few edges hanging on and those are the most important edges inside the image. They will help us to define the sharpness. So go ahead and apply a Radius value of 3 pixels, click OK. Now we don't like the gray, right? We like the darkness, we like the lightness, we don't like the gray. We want to drop the gray away. If that sounds like a blend mode to you, good job. The blend mode we want to apply of course, is a Contrast blend mode and our bet is going to be Overlay. All of the Contrast modes treat gray as neutral, so it will drop away and the blacks and whites hang on. And Overlay is just a good sensible mode for this kind of effect.
So I am going to press Shift+Alt+O or Shift+Option+O on the Mac with one of my Selection tools active in order to apply the Overlay mode to the sharpen layer and notice the difference. This is without that layer, this is with that layer. It's a pretty subtle difference so far, that's why we need to increase the contrast of this layer. Now if we had applied High Pass as a smart filter to the smart object, to the background smart object here, then this is as far we would be able to go. We could apply High Pass with a Radius of 3 and then we could of course, apply the Overlay Blend mode but we couldn't increase the contrast of the effect and so this is all we would get. That's no good. We have to increase the contrast of the effect. So we cannot use smart filters. It's very unfortunate.
Anyway I am going to go ahead and press Ctrl+L or Command+L on the Mac to bring up the Levels dialog box and this is how we essentially crank up the Amount value. That Amount value that we had available to us inside of the Smart Sharpen dialog box. I am going to send the Black point value to a 100 and the White point value to 155. So in other words we are adding a 100 to the Black point, we are subtracting a 100 from the White point. So we are taking this little funnel of colors right there, upside down funnel of colors in the histogram and we are spreading them out and we are exaggerating the contrast like crazy. I will click OK and now we have a ton of sharpening going on as a result. Not only that, we are really over sharpening the image at this point, but notice that it's affecting all layers below it.
So it's affecting multiple layers at a time and you can see that we have pretty much dropped out the crimson colors that were interfering with the blouse. We can see the yellow blouse once again and we are actually going to make it even cleaner in the next exercise. But for now, things are looking pretty darn good. They are definitely looking sharp. Although, you might say, I think this is overly sharpening. This is too much sharpness. It's certainly less subtle than what we had with the Smart Sharpen filter. Well we are going to curb the sharpness and we are going to isolate the sharpness just to the most essential details inside of the image, so that she looks great, no pores are sharpened and we are going to do it using a Density Mask in the very next exercise.
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