Photoshop 6 for Windows Bible- P17

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Photoshop 6 for Windows Bible- P17:If you are reading this foreword, it probably means that you’ve purchased a copy of Adobe Photoshop 6.0, and for that I and the rest of the Photoshop team at Adobe thank you. If you own a previous edition of the Photoshop Bible, you probably know what to expect. If not, then get ready for an interesting trip.

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Chapter 10 ✦ Corrective Filtering 449 Soft Sharpened, Threshold: 20 Sharpened, Threshold: 0 Figure 10-14: The original Ike is a bit soft (left), a condition I can remedy with Unsharp Mask. Leaving the Threshold value set to 0 brings out the film grain (middle), but raising the value results in equally unattractive artifacts (right). While we wait for Photoshop to give us a better Threshold — one with a Fuzziness slider or similar control — you can create a better Threshold using a very simple masking technique. Using a few filters that I explore at greater length throughout this chapter and the next, you can devise a selection outline that traces the essen- tial edges in the image — complete with fuzzy transitions — and leaves the non- edges unmolested. So get out your favorite old vintage photograph and follow along with these steps. STEPS: Creating and Using an Edge Mask 1. Duplicate one of the color channels. Bring up the Channels palette and drag one of the color channels onto the little page icon. Ike is a grayscale image, so I duplicate the one and only channel. 2. Choose Filter ➪ Stylize ➪ Find Edges. As I explain in Chapter 11, the Find Edges filter automatically traces the edges of your image with thick, gooey outlines that are ideal for creating edge masks. 3. Press Ctrl+I. Or choose Image ➪ Adjust ➪ Invert. Find Edges produces black lines against a white background, but in order to select your edges, you need white lines against a black background. The Invert command reverses the lights and darks in the mask, as in the first example in Figure 10-15.
450 Part III ✦ Selections, Masks, and Filters Find Edges, Invert Sharpened edges Find edge mask Figure 10-15: I copy a channel, find the edges, and invert (left). I then apply a string of filters to expand and soften the edges (middle). After converting the mask to a selection outline, I reapply Unsharp Mask with winning results (right). 4. Choose Filter ➪ Noise ➪ Median. You need fat, gooey edges, and the current ones are a bit tenuous. To firm up the edges, choose the Median filter, enter a value of 2 (or thereabouts), and press Enter. 5. Choose Filter ➪ Other ➪ Maximum. The next step is to thicken up the edges. The Maximum filter expands the white areas in the image, serving much the same function in a mask as Select ➪ Modify ➪ Expand serves when editing a selection outline. Enter 4 for the Radius value and press Enter. 6. Choose Filter ➪ Blur ➪ Gaussian Blur. Unfortunately, the Maximum filter results in a bunch of little squares that don’t do much for our cause. You can merge the squares into a seamless line by choosing the Gaussian Blur command and entering 4, the same radius you entered for Maximum. Then press Enter. The completed mask is pictured in the second example of Figure 10-15. Though hardly an impressive sight to the uninitiated eye, you’re looking at the perfect edge mask — soft, natural, and extremely accurate. 7. Return to the standard composite view. Press Ctrl+tilde (~) in a color image. In a grayscale image, press Ctrl+1. 8. Convert the mask to a selection outline. Ctrl-click the mask name in the Channels palette. Photoshop selects the most essential edges in the image without selecting the grain.
Chapter 10 ✦ Corrective Filtering 451 9. Choose Filter ➪ Sharpen ➪ Unsharp Mask. In the last example in Figure 10-15, I applied the highest permitted Amount value, 500 percent, and a Radius of 2.0. 10. Whatever values you use, make sure the Threshold is set to 0. And always leave it at 0 from this day forward. In case Figures 10-14 and 10-15 are a little too subtle, I include enlarged views of the great general’s eyes in Figure 10-16. The top eyes show the result of using the Threshold value, the bottom eyes were created using the edge mask. Which ones appear sharper and less grainy to you? Figure 10-16: Enlarged views of the last examples from Figures 10-14 (top) and 10-15 (bottom). A good edge mask beats the Threshold value every time. Using the High Pass filter The High Pass filter falls more or less in the same camp as the sharpening filters but is not located under the Filter ➪ Sharpen submenu. This frequently overlooked gem enables you to isolate high-contrast image areas from their low-contrast counterparts. When you choose Filter ➪ Other ➪ High Pass, Photoshop offers a single option: the familiar Radius value, which can vary from 0.1 to 250.0. As demonstrated in Figure 10-17, high Radius values distinguish areas of high and low contrast only slightly. Low values change all high-contrast areas to dark gray and low-contrast areas to a slightly lighter gray. A value of 0.1 (not shown) changes all pixels in an image to a single gray value and is therefore useless.
452 Part III ✦ Selections, Masks, and Filters 100.0 50.0 35.0 20.0 10.0 5.0 3.5 2.0 1.0 Figure 10-17: The results of separating high- and low-contrast areas in an image with the High Pass filter set at eight different Radius values. Applying High Pass to individual color channels In my continuing series of color plates devoted to adding a bit of digital color to the ages-old game of chess, Color Plate 10-5 shows the results of applying the High Pass filter set to a Radius value of 5.0 to the various color channels. This application is a pretty interesting use for this filter. When applied to all channels at once, High Pass
Chapter 10 ✦ Corrective Filtering 453 has an irritating habit of robbing the image of color in the low-contrast areas, just where the color is needed most. But when you apply it to a single channel, there’s no color to steal. In fact, the filter adds color. For example, because there is almost no contrast in the dark shadows, High Pass elevates the black to gray in each of the affected color channels. The gray in the red channel appears red, the gray in the red channel mixed with the gray in the green channel appears yellow, and so on. As a result, the filter imbues each image with a chalky glow. Note I enhanced the High Pass effect slightly in Color Plate 10-5 by increasing the contrast of each affected color channel using the Levels command. Using the Input option boxes at the top of the Levels dialog box, I changed the first value to 65 and the third value to 190, thereby compressing the color space equally on both the black and white sides. Had I not done this, the images would appear a little more washed out. (Not a lot, but I figure that you deserve the best color I can deliver.) For detailed information on the Levels command, read Chapter 17. Converting an image into a line drawing The High Pass filter is especially useful as a precursor to Image ➪ Adjust ➪ Threshold, which converts all pixels in an image to black and white (again, covered in Chapter 17). As illustrated in Figure 10-18, the Threshold command produces entirely different effects on images before and after you alter them with the High Pass filter. In fact, applying the High Pass filter with a low Radius value and then issuing the Threshold command converts your image into a line drawing. In the second row of examples in the figure, I followed Threshold with Filter ➪ Blur ➪ Gaussian Blur (the subject of the next section). I set the Gaussian Blur Radius value to 1.0. Like the Threshold option in the Unsharp Mask dialog box, the Threshold command results in harsh transitions; Gaussian Blur softens them to produce a more natural effect. Why change your image to a bunch of slightly different gray values and then apply a command such as Threshold? One reason is to create a mask, as discussed at length in the “Building a Mask from an Image” section of Chapter 9. (In Chapter 9, I used Levels instead of Threshold, but both are variations on the same theme.) You might also want to bolster the edges in an image. For example, to achieve the last row of examples in Figure 10-18, I layered the images prior to applying High Pass, Threshold, and Gaussian Blur. Then I monkeyed around with the Opacity setting and the blend mode to achieve an edge-tracing effect. Note I should mention that Photoshop provides several automated edge-tracing filters — including Find Edges, Trace Contour, and the Gallery Effects acquisition, Glowing Edges. But High Pass affords more control than any of these commands and permits you to explore a wider range of alternatives. Also worth noting, several Gallery Effects filters — most obviously Filter ➪ Sketch ➪ Photocopy — lift much of their code directly from High Pass. Although it may seem at first glance a strange effect, High Pass is one of the seminal filters in Photoshop.
454 Part III ✦ Selections, Masks, and Filters 5.0 2.5 1.0 Threshold and Gaussian Blur Opacity: 45%, Overlay mode Figure 10-18: Several applications of the High Pass filter with low Radius values (top row), followed by the same images subject to Image ➪ Adjust ➪ Threshold and Filter ➪ Blur ➪ Gaussian Blur (middle). I then layered the second row onto the first and modified the Opacity and blend mode settings to create the third row.
Chapter 10 ✦ Corrective Filtering 455 Blurring an Image The commands under the Filter ➪ Blur submenu produce the opposite effects of their counterparts under the Filter ➪ Sharpen submenu. Rather than enhancing the amount of contrast between neighboring pixels, the Blur filters diminish contrast to create softening effects. Applying the Gaussian Blur filter The preeminent Blur filter, Gaussian Blur, blends a specified number of pixels incre- mentally, following the bell-shaped Gaussian distribution curve I touched on earlier. When you choose Filter ➪ Blur ➪ Gaussian Blur, Photoshop produces a single Radius option box, in which you can enter any value from 0.1 to 250.0. (Beginning to sound familiar?) As demonstrated in Figure 10-19, Radius values of 1.0 and smaller blur an image slightly; moderate values, between 1.0 and 5.0, turn an image into a rude approximation of life without my glasses on; and higher values blur the image beyond recognition. Moderate to high Radius values can be especially useful for creating that hugely amusing Star Trek Iridescent Female effect. This is the old Star Trek, of course. Captain Kirk meets some bewitching ambassador or scientist who has just beamed on board. He takes her hand in sincere welcome as he gives out with a lecherous grin and explains how truly honored he is to have such a renowned guest in his transporter room, and so charming to boot. Then we see it — the close-up of the fetching actress shrouded in a kind of gleaming halo that prevents us from discern- ing if her lips are chapped or perhaps she’s hiding an old acne scar, because some cockeyed cinematographer smeared Vaseline all over the camera lens. I mean, what wouldn’t you give to be able to recreate this effect in Photoshop? Unfortunately, I don’t have any images of actresses adorned in futuristic go-go boots, so Constantine cum Rambo will have to do in a pinch. The following steps explain how to make the colossal head glow as demonstrated in Figure 10-20. STEPS: The Captain Kirk Myopia Effect 1. Press Ctrl+A to select the entire image. If you only want to apply the effect to a portion of the image, feather the selection with a radius in the neighborhood of 5 to 8 pixels. 2. Choose Filter ➪ Blur ➪ Gaussian Blur. Enter some unusually large value into the Radius option box — say, 8.0 — and press Enter. 3. Press Ctrl+Shift+F to bring up the Fade dialog box. To achieve the effects shown in Figure 10-20, I reduced the Opacity value to 70 percent, making the blurred image slightly translucent. This way, you can see the hard edges of the original image through the filtered one.
456 Part III ✦ Selections, Masks, and Filters 4. You can achieve additional effects by selecting options from the Mode pop-up menu. For example, I created the upper-right example in the figure by selecting the Screen option, which uses the colors in the filtered image to lighten the original. I created the two bottom examples in the figure by applying the Darken and Lighten options. 0.3 0.6 1.0 1.5 2.0 3.5 5.0 10.0 50.0 Figure 10-19: The results of blurring an image with the Gaussian Blur filter using eight different Radius values, ranging from slightly out of focus to Bad Day at the Ophthalmologist’s Office.
Chapter 10 ✦ Corrective Filtering 457 Normal Screen Darken Lighten Figure 10-20: After blurring the image, I chose Edit ➪ Fade Gaussian Blur and changed the Opacity value to 70 percent. Then I applied the labeled blend modes to alter the image further. Color Plate 10-6 shows an image that’s more likely to interest Captain Kirk. It shows a young agrarian woman subject to most of the same settings I applied earlier to Constantine. Again, I applied the Gaussian Blur filter with a Radius of 8.0. Then I used Edit ➪ Fade Gaussian Blur to adjust the Opacity value and blend mode. The upper-left image shows the Normal mode, but the upper-right image shows the Luminosity mode. In this case, the Screen mode resulted in a washed-out effect, whereas Luminosity yielded an image with crisp color detail and fuzzy brightness values. As a result, there are some interesting places where the colors leap off her checkered dress. As in Figure 10-20, the bottom two images show the effects of the Darken and Lighten modes. You know, though, as I look at this woman, I’m beginning to have my doubts about her and Captain Kirk. I mean, she has Scotty written all over her.
458 Part III ✦ Selections, Masks, and Filters The preset blurring filters Neither of the two preset commands in the Filter ➪ Blur submenu, Blur and Blur More, can distribute its blurring effect over a bell-shaped Gaussian curve. For that reason, these two commands are less functional than the Gaussian Blur filter. However, just so you know where they stand in the grand Photoshop focusing scheme, Figure 10-21 shows the effect of each preset command and the nearly equivalent effect created with the Gaussian Blur filter. Figure 10-21: The effects of the two preset blurring filters (top row) compared with their Gaussian Blur equivalents (bottom row), which are labeled according to Radius values. Blur Blur More 0.3 0.7 Antialiasing an image If you have a particularly jagged image, such as a 256-color GIF file, there’s a better way to soften the rough edges than applying the Gaussian Blur filter. The best solution is to antialias the image. How? After all, Photoshop doesn’t offer an Antialias filter. Well, think about it. Back in the “Softening selection outlines” section of Chapter 8, I described how Photoshop antialiases a brushstroke or selection outline at twice its normal size and then reduces it by 50 percent and applies bicubic interpolation. You can do the same thing with an image. Choose Image ➪ Image Size and enlarge the image to 200 percent of its present size. Make sure that the Resample Image check box is turned on and set to Bicubic. (You can also experiment with Bilinear for a slightly different effect, but don’t use Nearest
Chapter 10 ✦ Corrective Filtering 459 Neighbor.) Next, turn right around and choose Image ➪ Image Size again, but this time shrink the image by 50 percent. The top-left example in Figure 10-22 shows a jagged image subject to this effect. I used Image ➪ Adjust ➪ Posterize to reduce Moses to four colors. It’s ugly, but it’s not unlike the kind of images you may encounter, particularly if you have access to an aging image library. To the right is the same image subject to Gaussian Blur with a very low Radius value of 0.5. Rather than appearing softened, the result is just plain fuzzy. Jagged original Gaussian Blur, 0.5 Antialiased Antialiased x 4 Figure 10-22: A particularly jagged image (top left) followed by the image blurred using a filter (top right). By enlarging and reducing the image one or more times (bottom left and right), I soften the pixels without making them appear blurry. The enlarged details show each operation’s effect on the individual pixels.
460 Part III ✦ Selections, Masks, and Filters However, if I instead enlarge and reduce the image with the Image Size command, I achieve a true softening effect, as shown in the lower-left example in the figure, commensurate with Photoshop’s antialiasing options. Even after enlarging and reducing the image four times in a row — as in the bottom-right example — I don’t make the image blurry, I simply make it softer. Directional blurring In addition to its everyday blurring functions, Photoshop provides two directional blurring filters, Motion Blur and Radial Blur. Instead of blurring pixels in feathered clusters like the Gaussian Blur filter, the Motion Blur filter blurs pixels in straight lines over a specified distance. The Radial Blur filter blurs pixels in varying degrees depending on their distance from the center of the blur. The following pages explain both of these filters in detail. Motion blurring The Motion Blur filter makes an image appear as if either the image or camera was moving when you shot the photo. When you choose Filter ➪ Blur ➪ Motion Blur, Photoshop displays the dialog box shown in Figure 10-23. You enter the angle of movement into the Angle option box. Alternatively, you can indicate the angle by dragging the straight line inside the circle on the right side of the dialog box, as shown in the figure. (Notice that the arrow cursor actually appears outside the circle. Once you begin dragging on the line, you can move the cursor anywhere you want and still affect the angle.) Figure 10-23: Drag the line inside the circle to change the angle of the blur.
Chapter 10 ✦ Corrective Filtering 461 You then enter the distance of the movement in the Distance option box. Photoshop permits any value between 1 and 999 pixels. The filter distributes the effect of the blur over the course of the Distance value, as illustrated by the examples in Figure 10-24. Original 50 pixels 100 pixels 200 pixels 300 pixels 500 pixels Figure 10-24: A single black rectangle followed by five different applications of the Motion Blur filter. Only the Distance value varied, as labeled. A 0-degree Angle value was used in all five examples. Note Mathematically speaking, Motion Blur is one of Photoshop’s simpler filters. Rather than distributing the effect over a Gaussian curve — which one might argue would produce a more believable effect — Photoshop creates a simple linear distribution, peaking in the center and fading at either end. It’s as if the program took the value you specified in the Distance option, created that many clones of the image, offset half the clones in one direction and half the clones in the other — all spaced 1 pixel apart — and then varied the opacity of each.
462 Part III ✦ Selections, Masks, and Filters Using the Wind filter The problem with the Motion Blur filter is that it blurs pixels in two directions. If you want to distribute pixels in one absolute direction or the other, try the Wind filter, which you can use either on its own or in tandem with Motion Blur. When you choose Filter ➪ Stylize ➪ Wind, Photoshop displays the Wind dialog box shown in Figure 10-25. You can select from three methods and two directions to distribute the selected pixels. Figure 10-26 compares the effect of the Motion Blur filter to each of the three methods offered by the Wind filter. Notice that the Wind filter does not blur pixels. Rather, it evaluates a selection in 1-pixel-tall horizontal strips and offsets the strips randomly inside the image. Figure 10-25: Use the Wind filter to randomly distribute a selection in 1-pixel horizontal strips in one of two directions. To get the best results, try combining the Motion Blur and Wind filters with a translu- cent selection. For example, to create Figure 10-27, I cloned the entire image to a new layer and applied the Wind command twice, first selecting the Stagger option and then selecting Blast. Next, I applied the Motion Blur command with a 0-degree angle and a Distance value of 30. I then set the Opacity option in the Layers palette to 80 percent and selected Lighten from the blend mode pop-up menu.
Chapter 10 ✦ Corrective Filtering 463 The result is a perfect blend between two worlds. The motion effect in Figure 10-27 doesn’t obliterate the image detail, as the Wind filter does in Figure 10-26. And the motion appears to run in a single direction — to the right — something you can’t accomplish using Motion Blur on its own. Motion Blur Wind Blast Stagger Figure 10-26: The difference between the effects of the Motion Blur filter (upper left) and the Wind filter (other three). In each case, I selected From the Right from the Direction radio buttons. Radial blurring Choosing Filter ➪ Blur ➪ Radial Blur displays the Radial Blur dialog box shown in Figure 10-28. The dialog box offers two Blur Method options: Spin and Zoom.
464 Part III ✦ Selections, Masks, and Filters Figure 10-27: The result of combining the Wind and Motion Blur filters with a translucent selection. Figure 10-28: Drag inside the Blur Center grid to change the point about which the Radial Blur filter spins or zooms the image. If you select Spin, the image appears to be rotating about a central point. You spec- ify that point by dragging in the grid inside the Blur Center box (as demonstrated in the figure). If you select Zoom, the image appears to rush away from you, as if you were zooming the camera while shooting the photograph. Again, you specify the central point of the Zoom by dragging in the Blur Center box. Figure 10-29 features examples of both settings.
Chapter 10 ✦ Corrective Filtering 465 Spin, Draft Spin, Best Zoom, Draft Zoom, Best Figure 10-29: Four examples of the Radial Blur filter set to both Spin and Zoom, subject to different Quality settings (left and right). I specified Amount values of 10 pixels for the Spin examples and 30 for the Zooms. Each effect is centered about the right eye (your right, that is). After selecting a Blur Method option, you can enter any value between 1 and 100 in the Amount option box to specify the maximum distance over which the filter blurs pixels. (You can enter a value of 0, but doing so merely causes the filter to waste time without producing an effect.) Pixels farthest away from the center point move the most; pixels close to the center point barely move at all. Keep in mind that large values take more time to apply than small values. The Radial Blur filter, incidentally, qualifies as one of Photoshop’s most time-consuming operations.
466 Part III ✦ Selections, Masks, and Filters Select a Quality option to specify your favorite time/quality compromise. The Good and Best Quality options ensure smooth results by respectively applying bilinear and bicubic interpolation (as explained in the “General preferences” section of Chapter 2). However, they also prolong the amount of time the filter spends calculating pixels in your image. The Draft option diffuses an image, which leaves a trail of loose and randomized pixels but takes less time to complete. I used the Draft setting to create the left-hand images in Figure 10-29; I selected the Best option to create the images on the right. Blurring with a threshold The purpose of the Filter ➪ Blur ➪ Smart Blur is to blur the low-contrast portions of an image while retaining the edges. This way, you can downplay photo grain, blemishes, and artifacts without harming the real edges in the image. (If you’re familiar with Filter ➪ Pixelate ➪ Facet, it may help to know Smart Blur is essentially a customizable version of that filter.) The two key options inside the Smart Blur dialog box (see Figure 10-30) are the Radius and Threshold slider bars. As with all Radius options, this one expands the number of pixels calculated at a time as you increase the value. Meanwhile, the Threshold value works just like the one in the Unsharp Mask dialog box, specifying how different two neighboring pixels must be to be considered an edge. Figure 10-30: The Smart Blur filter lets you blur the low-contrast areas of an image without harming the edges.
Chapter 10 ✦ Corrective Filtering 467 But the Threshold value has a peculiar and unexpected effect on the Radius. The Radius value actually produces more subtle effects if you raise the value beyond the Threshold. For example, take a look at Figure 10-31. Here we have a grid of images subject to different Radius and Threshold values. (The first value below each image is the radius.) In the top row of the figure, the 5.0 radius actually produces a more pronounced effect than its 20.0 and 60.0 cousins. This is because 5.0 is less than the 10.0 threshold, while 20.0 and 60.0 are more. 5.0, 10.0 20.0, 10.0 60.0, 10.0 5.0, 30.0 20.0, 30.0 60.0, 30.0 5.0, 80.0 20.0, 80.0 60.0, 80.0 Figure 10-31: Combinations of different Radius (first number) and Threshold (second) values. Notice that the most dramatic effects occur when the radius is equal to about half the threshold.
468 Part III ✦ Selections, Masks, and Filters The Quality settings control the smoothness of the edges. The High setting takes more time than Medium and Low, but it looks smoother as well. (I set the value to High to create all the effects in Figure 10-31.) The two additional Mode options enable you to trace the edges defined by the Threshold value with white lines. Overlay Edge shows image and lines, while Edge Only shows just the traced lines. About the only practical purpose for these options is to monitor the precise effect of the Threshold setting in the preview box. Otherwise, the Edge options are clearly relegated to special effects. Frankly, I’m not convinced that Smart Blur is quite ready for prime time. You already know what I think of the Threshold option, and it hasn’t gotten any better here. Without control over the transitions between focused and unfocused areas, things are going to look pretty strange. Tip The better way to blur low-contrast areas is to create an edge mask, as I explained back in the “Sharpening grainy photographs” section. Just reverse the selection by choosing Select ➪ Inverse and apply the Gaussian Blur filter. Figure 10-32 shows how the masking technique compares with Smart Blur. In the first image, I applied Unsharp Mask with a Threshold of 20. Then I turned around and applied Smart Blur with a Radius of 2.0 and a Threshold of 20.0, matching the Unsharp Mask value. The result makes Ike look like he has dandruff coming out of every pore in his face. Figure 10-32: The difference between relying on Photoshop’s automated Threshold capabilities (left) and sharpening and blurring with the aid of an edge mask (right). Despite the advent of computers, a little manual labor still wins out over automation.