Photoshop 6 for Windows Bible- P16 potx

419 Chapter 9 ✦ Masks and Extractions When the mask is active, you can likewise toggle the display of the image by press- ing the tilde (~) key. Few folks know about this shortcut, but it’s a good one to assign to memory. It works whether the Channels palette is open or not, and it per- mits you to focus on the mask without moving your mouse all over the screen. Using a mask channel is different from using the quick mask mode in that you can edit either the image or the mask channel when viewing the two together. You can even edit two or more masks at once. To specify which channel you want to edit, click the channel name in the palette. To edit two channels at once, click one and Shift-click another. All active channel names appear highlighted. You can change the color and opacity of each mask independently of other mask channels and the quick mask mode. Double-click the mask channel name or choose the Channel Options command from the Channels palette menu. (This command is dimmed when editing a standard color channel, such as Red, Green, Blue, Cyan, Magenta, Yellow, or Black.) A dialog box similar to the one shown back in Figure 9-11 appears, but this one contains a Name option box so you can change the name of the mask channel. You can then edit the color overlay as described in the “Changing the red coating” section earlier in this chapter. If you ever need to edit a selection outline inside the mask channel using paint and edit tools, click the quick mask mode icon in the toolbox. It may sound a little like a play within a play, but you can access the quick mask mode even when working within a mask channel. Make sure the mask channel color is different from the quick mask color so you can tell what’s happening. Building a Mask from an Image So far, everything I’ve discussed in this chapter has been pretty straightforward. Now it’s time to see how the professionals do things. This final section in this chap- ter explains every step required to create a mask for a complex image. Here’s how to select the image you never thought you could select, complete with wispy little details such as hair. Take a gander at Figure 9-28 and see what I mean. I chose this subject not for her good looks or her generous supply of freckles, but for that hair. I mean, look at all that hair. Have you ever seen such a frightening image-editing subject in your life? Not only is this particular girl blessed with roughly 15 googol strands of hair, but every one of them is leaping out of her head in a different direction and at a differ- ent level of focus. Can you imagine selecting any one of them with the magnetic lasso or magic wand? No way. As demonstrated by the second example of Figure 9-28, these tools lack sufficient accuracy to do any good. Furthermore, you’d be fit for an asylum by the time you finished selecting the hairs with the pen tools, and the edges aren’t definite enough for Select➪ Color Range to latch onto. Tip Tip 420 Part III ✦ Selections, Masks, and Filters Figure 9-28: Have you ever wanted to select wispy details, such as the hair shown on left? You certainly aren’t going to make it with the magnetic lasso (right) or other selection tools. But with masks, it’s a piece of cake. So, what’s the solution? Manual masking. Although masking styles vary as widely as artistic style, a few tried-and-true formulas work for everyone. First, you peruse the channels in an image to find the channel that lends itself best to a mask. You’re looking for high degrees of contrast, especially around the edges. Next, you copy the channel and boost the level of contrast using Image ➪ Adjust ➪ Levels. (Some folks prefer Image➪ Adjust ➪ Curves, but Levels is more straightforward.) Then you paint inside the lines until you get the mask the way you want it. The only way to get a feel for masking is to try it out for yourself. The following steps explain exactly how I masked this girl and pasted her against a different background. The final result is so realistic, you’d think she was born there. STEPS: Selecting a Monstrously Complicated Image Using a Mask 1. Browse the color channels. Press Ctrl+1 to see the red channel, Ctrl+2 for green, and Ctrl+3 for blue. (This assumes you’re working inside an RGB image. You can also peruse CMYK and Lab images. If you’re editing a grayscale image, you have only one channel from which to choose— Black.) 421 Chapter 9 ✦ Masks and Extractions Figure 9-29 shows the three channels in my RGB image. Of the three, the red channel offers the most contrast between the hair, which appears very light, and the background, which appears quite dark. Figure 9-29: Of the three color channels, the red channel offers the best contrast between hair and background. 2. Copy the channel. Drag the channel onto the little page icon at the bottom of the Channels palette. (I naturally copy the red channel.) Now you can work on the channel to your heart’s content without harming the image itself. 3. Choose Filter ➪ Other ➪ High Pass. The next thing you want to do is to force Photoshop to bring out the edges in the image so you don’t have to hunt for them manually. And when you think edges, you should think filters. All of Photoshop’s edge-detection prowess is packed into the Filter menu. Several edge-detection filters are available to you— Unsharp Mask, Find Edges, and many others that I discuss in Chapter 10. But the best filter for finding edges inside a mask is Filter ➪ Other ➪ High Pass. High Pass selectively turns an image gray. High Pass may sound strange, but it’s quite useful. The filter turns the non-edges completely gray while leaving the edges mostly intact, thus dividing edges and non-edges into different brightness camps, based on the Radius value in the High Pass dialog box. Unlike in most filters, a low Radius value produces a more pronounced effect than a high one, in effect locating more edges. Red Blue Green 422 Part III ✦ Selections, Masks, and Filters Figure 9-30 shows the original red channel on left with the result of the High Pass filter on right. I used a Radius of 10, which is a nice, moderate value. The lower you go, the more edges you find and the more work you make for your- self. A Radius of 3 is accurate, but it’ll take you an hour to fill in the mask. Granted, 10 is less accurate, but if you value your time, it’s more sensible. Figure 9-30: After copying the red channel (left), I apply the High Pass filter with a Radius value of 10 to highlight the edges in the image (right). 4. Choose Image ➪ Adjust ➪ Levels (Ctrl+L). After adding all that gray to the image, follow it up by increasing the contrast. And the best command for enhancing contrast is Levels. Although I discuss this command in-depth in Chapter 17, here’s the short version: Inside the Levels dialog box, raise the first Input Levels value to make the dark colors darker, and lower the third Input Levels value to make the light colors lighter. (For now you can ignore the middle value.) Figure 9-31 shows the result of raising the first Input Levels value to 110 and lowering the third value to 155. As you can see in the left-hand image, this gives me some excellent contrast between the white hairs and black back- ground. 423 Chapter 9 ✦ Masks and Extractions To demonstrate the importance of the High Pass command in these steps, I’ve shown what would happen if I had skipped Step 3 in the right-hand image in Figure 9-31. I applied the same Levels values as in the left image, and yet the image is washed out and quite lacking in edges. Look at that wimpy hair. It simply is unacceptable. Figure 9-31: Here are the results of applying the Levels command to the mask after the High Pass step (left) and without High Pass (right). As you can see, High Pass has a pronounced effect on the edge detail. 5. Use the lasso tool to remove the big stuff you don’t need. By way of High Pass and Levels, Photoshop has presented you with a complex coloring book. From here on, it’s a matter of coloring inside the lines. To simplify things, get rid of the stuff you know you don’t need. All you care about is the area where the girl meets her background— mostly hair and arms. Everything else goes to white or black. For example, in Figure 9-32, I selected a general area inside the girl by Alt-click- ing with the lasso tool. Then I filled it with white by pressing Ctrl+Delete. I also selected around the outside of the hair and filled it with black. At all times, I was careful to stay about 10 to 20 pixels away from the hair and other edges; these I need to brush in carefully with the eraser. (Be sure to press Ctrl+D to eliminate the selection before continuing to the next step.) 424 Part III ✦ Selections, Masks, and Filters Figure 9-32: To tidy things up a bit, I selected the general areas inside and outside the girl with the lasso tool and filled them with white or black (left). Then I painted inside the lines with the block eraser (right). 6. Erase inside the lines with the block eraser. This is the most time-consuming part. You now have to paint inside the lines to make the edge pixels white (selected) or black (not). I like to use the block eraser because it’s a hard-edged block. See, Photoshop has already presented me with these lovely and accurate edges. I don’t want to gum things up by introducing new edges with a soft paint- brush or airbrush. The block eraser is hard, you can easily see its exact bound- aries, and it automatically adjusts as you zoom in and out — affecting fewer pixels at higher levels of magnification, which is what you need. When working in a mask, the eraser always paints in the background color. So, use the X key to toggle the background color between white and black. The second example in Figure 9-32 shows the fruits of my erasing. As you can see, I make a few judgment calls and decide — sometimes arbitrarily — where the hair gets so thick that background imagery won’t show through. You may even disagree with some of my eraser strokes. But you know what? It doesn’t matter. Despite whatever flaws I may have introduced, my mask is more than accurate enough to select the girl and her unruly hair, as I soon demonstrate. 7. Switch to the color composite view. Press Ctrl+tilde (~). Or if you’re working in a grayscale image, press Ctrl+1. By the way, now is a good time to save the image if you haven’t already done so. 425 Chapter 9 ✦ Masks and Extractions 8. Ctrl-click the mask channel to convert it to a selection. This mask is ready to go prime time. 9. Ctrl-drag the selection and drop it into a different image. Figure 9-33 shows the result of dropping the girl into a background of rolling California hills. Thanks to my mask, she looks as natural in her new environment as she did in her previous one. In fact, an uninitiated viewer might have difficulty believ- ing this isn’t how she was originally photographed. But if you take a peek at Figure 9-29, you can confirm that Figure 9-33 is indeed an artificial composite. I lost a few strands of hair in the transition, but she can afford it. Figure 9-33: Thanks to masking, our girl has found a new life in Southern California. Now she’s ready to finally put on those sunglasses. The grayscale Figure 9-33 looks great but, in all honesty, your compositions may not fare quite so well in color, as illustrated by the first girl in Color Plate 9-3. Her hair is fringed with blue, an unavoidable holdover from her original blue background. 426 Part III ✦ Selections, Masks, and Filters The solution is to brush in the color from her new background. Using the paint- brush tool set to the Color brush mode, you can Alt-click in the Background layer to lift colors from the new background and then paint them into the hair. I also took the liberty of erasing a few of the more disorderly hairs, especially the dark ones above her head. (I used a soft paintbrush-style eraser, incidentally, not the block.) After a minute or two of painting and erasing, I arrived at the second girl in the color plate. Now if that isn’t compositing perfection, I don’t know what is. ✦✦✦ Corrective Filtering Filter Basics In Photoshop, filters enable you to apply automated effects to an image. Though named after photographers’ filters, which typically correct lighting and perspective fluctuations, Photoshop’s filters can accomplish a great deal more. You can slightly increase the focus of an image, introduce random pixels, add depth to an image, or completely rip it apart and reassemble it into a hurky pile of goo. Any number of special effects are made available via filters. At this point, a little bell should be ringing in your head, telling you to beware of standardized special effects. Why? Because everyone has access to the same filters that you do. If you rely on filters to edit your images for you, your audi- ence will quickly recognize your work as poor or at least unremarkable art. Imagine this scenario: You’re wasting away in front of your TV, flipping aimlessly through the channels. Just as your brain is about to shrivel and implode, you stumble across the classic “Steamroller” video. Outrageous effects, right? Peter Gabriel rides an imaginary roller coaster, bumper cars crash playfully into his face, fish leap over his head. You couldn’t be more amused or impressed. As the video fades, you’re so busy basking in the glow that you neglect for a split second to whack the channel-changer. Before you know it, you’re midway through an advertisement for a monster truck rally. Like the video, the ad is riddled with special effects — spinning letters, a reverberating voice-over slowed down to an octave below the narrator’s normal pitch, and lots of big machines filled with little men filled with single brain cells working overtime. 10 10 CHAPTER ✦✦✦✦ In This Chapter An overview of corrective, destructive, and effects filters Mixing a filtered image with the original Fixing the focus of an image with Unsharp Mask Enhancing a grainy photograph using a custom edge mask Highlighting edges with the High Pass filter Creating glowing images with Gaussian Blur Feathering a selection using Maximum and Gaussian Blur A complete guide to the filters in the Noise submenu Sharpening images with lots of compression artifacts Reducing moiré patterns in scanned images ✦✦✦✦ 428 Part III ✦ Selections, Masks, and Filters In and of themselves, these special effects aren’t bad. There was probably even a time when you thought that spinning letters and reverberating voice-overs were hot stuff. But sometime after you passed beyond preadolescence, you managed to grow tired of these particular effects. You’ve come to associate them with raunchy, local car-oriented commercials. Certainly these effects are devoid of substance, but, more importantly, they’re devoid of creativity. This chapter and the next, therefore, are about the creative application of special effects, as is Chapter A on the CD at the back of this book. Rather than trying to show an image subject to every single filter — a service already performed quite adequately by the manual included with your software— these chapters explain exactly how the most important filters work and offer some concrete ways to use them. You also learn how to apply several filters in tandem and how to use filters to edit images and selection outlines. My goal is not so much to teach you what filters are available — you can find that out by tugging on the Filter menu — but how and when to use filters. A first look at filters You access Photoshop’s special effects filters by choosing commands from the Filter menu. These commands fall into two general camps — corrective and destructive. Corrective filters Corrective filters are workaday tools that you use to modify scanned images and prepare an image for printing or screen display. In many cases, the effects are subtle enough that the viewer won’t even notice that you applied a corrective filter. As demonstrated in Figure 10-1 and Color Plate 10-1, these filters include those that change the focus of an image, enhance color transitions, and average the colors of neighboring pixels. Find these filters in the Filter ➪ Blur, Noise, Sharpen, and Other submenus. Many corrective filters have direct opposites. Blur is the opposite of Sharpen, Add Noise is the opposite of Median, and so on. This is not to say that one filter entirely removes the effect of the other; only reversion functions such as the History palette provide that capability. Instead, two opposite filters produce contrasting effects. Corrective filters are the subject of this chapter. Although they number fewer than their destructive counterparts, I spend more time on them because they represent the functions you’re most likely to use on a day-to-day basis. [...]... apply the next filter Therefore, you may find it more helpful to copy a selection to a separate layer (Ctrl+J) before applying a filter This way, you can perform other operations, and even apply many filters in a row, before mixing the filtered image with the underlying original Chapter 10 ✦ Corrective Filtering Filtering inside a border And here’s another reason to layer before you filter: If your... value of 1.0 The edges will look a little thick on-screen, but they’ll print fine ✦ For high-resolution images — around 300 ppi — try a Radius of 2.0 Because Photoshop prints more pixels per inch, the edges have to be thicker to remain nice and visible Tip If you’re looking for a simple formula, I recommend 0.1 of Radius for every 15 ppi of final image resolution That means 75 ppi warrants a Radius of... must occur for Photoshop to recognize them as an edge Suppose that the brightness values of neighboring pixels are 10 and 20 If you set the Threshold value to 5, Photoshop reads both pixels, notes that the difference between their brightness values is more than 5, and treats them as an edge If you set the Threshold value to 20, however, Photoshop passes them by A low Threshold value, therefore, causes... menu, Photoshop applies the filter to the selected portion of the image on the current layer If no portion of the image is selected, Photoshop applies the filter to the entire image Therefore, if you want to filter every nook and cranny of the current layer, press Ctrl+D to cancel any existing selection outline and then choose the desired command External plug-ins Some filters are built into the Photoshop. .. inside this latest folder, Photoshop sees through your clever ruse and displays the exact same filters you always see under their same submenus in the Filter menu The only purpose of the subfolders is to keep things tidy, so that you don’t have to look through a list of 6, 000 files Chapter 10 ✦ Corrective Filtering Previewing filters For years, the biggest problem with Photoshop s filters was that... predict the outcome of an effect You just had to tweak your 15,000 meaningless settings and hope for the best But today, life is much better Photoshop 3 introduced previews, Version 4 made them commonly available to all but the most gnarly filters, and Versions 5 and 6 had the good sense to leave well enough alone Photoshop offers two previewing capabilities: ✦ Dialog box previews: Labeled in Figure 10-4,... applicable to color images only, so I had to convert Constantine to the RGB mode before applying the filter Destructive filters produce way-cool effects, and many people gravitate toward them when first experimenting with Photoshop But the filters invariably destroy the original clarity and composition of the image Granted, every Photoshop function is destructive to a certain extent, but destructive filters... shown in Figure 10 -6 — you don’t want Photoshop to factor the border into the filtering operation To avoid this, select the image inside the border and press Ctrl+J to layer it prior to applying the filter The reason is that most filters take neighboring pixels into consideration even if they are not selected By contrast, when a selection floats, it has no neighboring pixels, and therefore the filter... Layered Motion Blur Unsharp Mask Not layered Figure 10 -6: The results of applying two sample filters to images surrounded by borders In each case, only the image was selected; the border was not Layering the right examples prevented the borders from affecting the performance of the filters 437 438 Part III ✦ Selections, Masks, and Filters Figure 10 -6 shows the results of applying two filters discussed... the late Jurassic, pre -Photoshop epoch) Chapter 10 ✦ Corrective Filtering Even folks like me who used to operate stat cameras professionally never had the time to delve into the world of unsharp masking In addition — and much to the filter’s credit — Unsharp Mask goes beyond traditional camera techniques To understand Unsharp Mask — or Photoshop s other sharpening filters, for that matter — you first . want to do is to force Photoshop to bring out the edges in the image so you don’t have to hunt for them manually. And when you think edges, you should think filters. All of Photoshop s edge-detection. blend modes, Lighten and Overlay, with the Opacity value restored to 100 percent. 6 Photoshop 6 Tip Tip 4 36 Part III ✦ Selections, Masks, and Filters Figure 10-5: Press Ctrl+Shift+F to mix the. style, a few tried-and-true formulas work for everyone. First, you peruse the channels in an image to find the channel that lends itself best to a mask. You’re looking for high degrees of contrast,