Photoshop 6 for Windows Bible- P18 pps

479 Chapter 10 ✦ Corrective Filtering Averaging pixels with Median Another command in the Filter ➪ Noise submenu, Median removes noise by averaging the colors in an image, one pixel at a time. When you choose Filter ➪ Noise➪ Median, Photoshop produces a Radius option box. For every pixel in a selection, the filter averages the colors of the neighboring pixels that fall inside the specified radius — ignoring any pixels that are so different that they might skew the average — and applies the average color to the central pixel. You can now enter any value between 1 and 100. However, even at the old limit, 16, significant blurring occurs, as you can see from the bottom-right example in Figure 10-41 (in the preceding section). At the maximum Radius value, you wind up with a sort of soft, blurry gradient, with all image detail obliterated. As with Gaussian Blur, you can achieve some very interesting and useful effects by backing off the Median filter with the Fade command. But rather than creating a Star Trek glow, Median clumps up details, giving an image a plastic, molded quality, as demonstrated by the examples in Figure 10-42. To create every one of these images, I applied the Median Filter with a Radius of 5 pixels. Then I pressed Ctrl+Shift+F to display the Fade dialog box and lowered the Opacity value to 70 percent. The only difference between one image and the next is the blend mode. Another difference between Gaussian Blur and Median is that Gaussian Blur destroys edges and Median invents new ones. This means you can follow up the Median filter with Unsharp Mask to achieve even more pronounced sculptural effects. I sharpened every one of the examples in Figure 10-42 using an Amount value of 150 percent and a Radius of 1.5. Sharpening a compressed image Digital cameras are the hottest thing in electronic imaging. You can take as many images as you like, download them to your computer immediately, and place them into a printed document literally minutes after snapping the picture. In the next five years, I have little doubt that you — yes, you — will purchase a digital camera (if you haven’t already). Unfortunately, the technology is still very young. And if you’re using one of the mid- or low-priced cameras —read that, under $500 — even the slightest application of the Unsharp Mask filter sometimes results in jagged edges and unsightly artifacts. These blemishes stem from a stingy supply of pixels, heavy-handed compression schemes (all based on JPEG), or both. The situation is improving; cameras at the high end of the consumer price range ($700 and up) can produce 3-megapixel images and often enable you to store uncompressed images in the TIFF format. But as with all good things in life, it will take a while for those options to be available in moderately priced equipment. 6 Photoshop 6 480 Part III ✦ Selections, Masks, and Filters Figure 10-42: After applying the Median filter, I reversed the effect slightly using Edit ➪ Fade Median. Although I varied the blend mode — as labeled beneath the images — the Opacity value remained a constant 70 percent. In the meantime, firm up the detail and smooth out the color transitions in your digital photos by applying a combination of filters — Median, Gaussian Blur, and Unsharp Mask — to a layered version of the image. The following steps tell all. If you own a digital camera, I encourage you to record these steps with the Actions palette, as explained in Chapter B on the CD accompanying this book. This way, you can set Photoshop to open squads of images, batch-process them, and save them in a separate folder, leaving you free to do something fun, like read more of this book. Note Normal Screen Darken Lighten 481 Chapter 10 ✦ Corrective Filtering STEPS: Adjusting the Focus of Digital Photos 1. Select the entire image and copy it to a new layer. That’s Ctrl+A, Ctrl+J. Figure 10-43 shows the image that I intend to sharpen, a picture of a friend’s child. Figure 10-43: I captured this youthful fellow with a low-end digital camera equipped with a removable fish-eye lens. How innocent and happy he looks — obviously not a computer user. 2. Choose Filter ➪ Noise ➪ Median. After processing several thousand of these images, I’ve found that a Radius value of 2 is almost always the optimal choice. But if the image is particularly bad, 3 may be warranted. 3. Choose Filter ➪ Blur ➪ Gaussian Blur. Now that you’ve gummed up the detail a bit and rubbed out most of the compression, use the Gaussian Blur filter with a Radius of 1.0 to blur the gummy detail slightly. This softens the edges that the Median filter creates. (You don’t want any fake edges, after all.) 4. Choose Filter ➪ Sharpen ➪ Unsharp Mask. All this blurring demands some intense sharpening. So apply Unsharp Mask with a maximum Amount value of 500 percent and a Radius of 1.0 (to match the Gaussian Blur radius). This restores most of the definition to the edges, as shown in Figure 10-44. 5. Lower the layer’s Opacity value. By itself, the filtered layer is a bit too smooth. So mix the filtered floater with the underlying original with an Opacity value between 30 and 50 percent. I found that I could go pretty high —45 percent — with Cooper. Kids have clearly defined details that survive filtering quite nicely. 482 Part III ✦ Selections, Masks, and Filters Figure 10-44: Thanks to Median, Gaussian Blur, and Unsharp Mask, Cooper is a much smoother customer. In fact, he’s beyond smooth — he’s a gummy kid. 6. Merge the image. Press Ctrl+E to send the layer down. 7. Continue to correct the image as you normally would. The examples in Figure 10-45 show the difference between applying the Unsharp Mask filter to the original image (top) and the filtered mixture (bottom). In both cases, I applied an Amount value of 200 percent and a Radius of 1.0. The top photo displays an unfortunate wealth of artifacts — particularly visible in the magnified eye — while the bottom one appears smooth and crisp. These steps work well for sharpening other kinds of compressed imagery, including old photographs that you over-compressed without creating backups, and images that you’ve downloaded from the Internet. If applying the Unsharp Mask filter brings out the goobers, try these steps instead. Cleaning up scanned halftones Photoshop offers one additional filter in the Filter ➪ Noise submenu called Dust & Scratches. The purpose of this filter is to remove dust particles, hairs, scratches, and other imperfections that may accompany a scan. The filter offers two options, Radius and Threshold. As long as the offending imperfection is smaller or thinner than the Radius value and different enough from its neighbors to satisfy the Threshold value, the filter deletes the spot or line and interpolates between the pixels around the perimeter. 483 Chapter 10 ✦ Corrective Filtering Figure 10-45: Here you can see the difference between sharpening a digital photograph right off the bat (top) and waiting to sharpen until after you’ve prepared the image with Median, Gaussian Blur, and Unsharp Mask (bottom). But like so many automated tools, this one works only when conditions are favorable. I’m not saying that you shouldn’t ever use it — in fact, you may always want to give this filter the first crack at a dusty image. But if it doesn’t work (as it probably won’t), don’t get your nose out of joint. Just hunker down and eliminate the imperfections manually using the rubber stamp tool, as explained in the “Touching up blemishes” section of Chapter 7. 484 Part III ✦ Selections, Masks, and Filters Now, as I say, Dust & Scratches was designed to get rid of gunk on a dirty scanner. But another problem that the filter may be able to eliminate is moiré patterns. These patterns appear when scanning halftoned images from books and magazines. See, any time you scan a printed image, you’re actually scanning a collection of halftone dots rather than a continuous-tone photograph. In most cases, the halftone pattern clashes with the resolution of the scanned image to produce rhythmic and distracting moirés. When scanning published photographs or artwork, take a moment to find out if what you’re doing is legal. It’s up to you to make sure that the image you scan is no longer protected by copyright— most, but not all, works over 75 years old are considered free game — or that your noncommercial application of the image falls under the fair-use umbrella of commentary or criticism. The Dust & Scratches filter can be pretty useful for eliminating moirés, particularly if you reduce the Threshold value below 40. But this also goes a long way toward eliminating the actual image detail, as shown in Color Plate 10-7. This figure features an image scanned from a previous issue of Macworld magazine. (Because I created the original image, Macworld probably won’t sue me, but you shouldn’t try it.) The left half of Color Plate 10-7 shows the individual color channels in the image; the right half shows the full-color image. I’ve blown up a detail in each image so that you can better see the pixels in the moiré pattern. The top example in the color plate shows the original scanned image with its awful moirés. (Actually, I’ve slightly exaggerated the moirés to account for any printing anomalies; but believe me, with or without enhancement, the image is a mess on screen.) The middle example shows the same image subject to the Dust & Scratches filter with a Radius of 2 and a Threshold value of 20. The moirés are gone, but the edges have all but disappeared as well. I’m tempted to describe this artwork using adjectives such as “soft” and “doughy,” and them are fightin’ words in the world of image editing. But what about that bottom example? How did I manage to eliminate the moirés and preserve the detail that is shown here? Why, by applying the Gaussian Blur, Median, and Unsharp Mask filters to individual color channels. The first step is to examine the channels independently (by pressing Ctrl+1, Ctrl+2, and Ctrl+3). You’ll likely find that each one is affected by the moiré pattern to a dif- ferent extent. In the case of this scan, all three channels need work, but the blue channel — the usual culprit — is the worst. The trick, therefore, is to eliminate the patterns in the blue channel and draw detail from the red and green channels. To fix the blue channel, I applied both the Gaussian Blur and Median commands in fairly hefty doses. I chose Filter ➪ Blur ➪ Gaussian Blur and specified a Radius value of 1.5 pixels, rather high considering that the image measures only about 300 pixels tall. Then I chose Filter ➪ Noise ➪ Median and specified a Radius of 2. Caution 485 Chapter 10 ✦ Corrective Filtering The result was a thickly modeled image with no moirés but little detail. To firm things up a bit, I chose Filter ➪ Sharpen ➪ Unsharp Mask and entered 200 percent for the Amount option and 1.5 for the Radius. I opted for this Radius value because it matches the Radius that I used to blur the image. When correcting moirés, a Threshold value of 0 is almost always the best choice. A higher Threshold value not only prevents the sharpening of moiré pattern edges but also ignores real edges, which are already fragile enough as it is. The green and red channels required incrementally less attention. After switching to the green channel, I applied the Gaussian Blur filter with a Radius of 1.0. Then I sharpened the image with the Unsharp Mask filter set to 200 percent and a Radius value of 0.5. In the red channel (Ctrl+1), I applied Gaussian Blur with a Radius value of 0.5. The gradual effect wasn’t enough to warrant sharpening. When you’re finished, switch back to the RGB view (Ctrl+0) to see the combined result of your labors. (Or keep an RGB view of the image up on screen by choosing Window➪ New Window.) The focus of the image will undoubtedly be softer than it was when you started. You can cure this to a limited extent by applying very dis- creet passes of the Unsharp Mask filter, say, with an Amount value of 100 percent and a low Radius value. Keep in mind that oversharpening may bring the patterns back to life or even uncover new ones. One last tip: Always scan halftoned images at the highest resolution available to your scanner. Then resample the scan down to the desired resolution using Image ➪ Image Size, as covered in Chapter 3. This step by itself goes a long way toward eliminating moirés. ✦✦✦ Tip Full-Court Filtering Destructive Filters Corrective filters enable you to eliminate image flaws and apply special effects. Destructive filters, on the other hand, are devoted solely to special effects. Even though Photoshop offers nearly twice as many destructive filters as corrective counterparts, destructive filters are less frequently used and ultimately less useful. Don’t get me wrong— these filters are a superb bunch. But because of their more limited appeal, I don’t explain each and every one of them. Rather, I concentrate on the ones that I think you’ll use most often, breeze over a handful of others, and let you discover on your own the ones that I ignore. In addition to explaining the commands found on the Filter menu, this chapter also explains the new Liquify command, which probably ought to be on the Filter menu but isn’t. Liquify enables you to shove pixels around your image by dragging them, providing a means for freeform, interactive distortion. A million wacky effects Oh heck, I guess I can’t just go and ignore half of the com- mands on the Filter menu — they’re not completely useless, after all. It’s just that you aren’t likely to use them more than once every lunar eclipse. So here are the briefest of all pos- sible descriptions of these filters: ✦ Color Halftone: Located under the Filter ➪ Pixelate sub- menu, this command turns an image into a piece of Roy Lichtenstein artwork, with big, comic-book halftone dots. Although scads of fun, the filter is ultimately a novelty that takes about a year and a half to apply. 6 Photoshop 6 11 11 CHAPTER ✦✦✦✦ In This Chapter Capsule descriptions of Photoshop’s special effects filters Clever ways to use the Pixelate filters Putting the Mezzotint filter to good use Applying the edge- enhancement filters, including Emboss and Find Edges Creating metallic effects with Bas Relief, Plastic Wrap, and Chrome Exploring new worlds with the help of the distortion filters Tugging at images with the Liquify filter Designing specialized gradations and other abstractions Transforming images in 3D space Changing a picture’s atmosphere using Clouds The complete inner workings of Lighting Effects ✦✦✦✦ 488 Part III ✦ Selections, Masks, and Filters ✦ Fragment: Ooh, it’s an earthquake! This lame filter repeats an image four times in a square formation and lowers the opacity of each to create a sort of jiggly effect. You don’t even have any options to control it. It’s quite possible I’m missing the genius behind Filter ➪ Pixelate ➪ Fragment. Then again, maybe not. ✦ Lens Flare: Found in the Render submenu, this filter adds sparkles and halos to an image to suggest light bouncing off the camera lens. Even though pho- tographers work their behinds off trying to make sure that these sorts of reflections don’t occur, you can add them after the fact. You can select from one of three Lens Type options, adjust the Brightness slider between 10 and 300 percent (though somewhere around 100 is bound to deliver the best results), and move the center of the reflection by dragging a point around inside the Flare Center box. In addition, you now can Alt-click inside the preview to position the center point numerically. If you want to add a flare to a grayscale image, first convert it to the RGB mode. Then apply the filter and convert the image back to grayscale. The Lens Flare filter is applicable to RGB images only. Here’s another great tip for using Lens Flare. Before choosing the filter, create a new layer, fill it with black, and apply the Screen blend mode (Shift+Alt+S with a non-painting tool selected). Now apply Lens Flare. You get the same effect as you would otherwise, but the effect floats above the background image, protecting your original image from harm. You can even move the lens flare around and vary the Opacity value, giving you more control over the final effect. ✦ Diffuse: Located in the Stylize submenu — as are the three filters that follow — Diffuse dithers the edges of color, much like the Dissolve brush mode dithers the edges of a soft brush. Diffuse is moderately useful but not likely to gain a place among your treasured few. ✦ Solarize: This single-shot command is easily Photoshop’s worst filter. It’s really just a color-correction effect that changes all medium grays in the image to 50 percent gray, all blacks and whites to black, and remaps the other colors to shades in between. (If you’re familiar with the Curves command, the map for Solarize looks like a pyramid.) It really belongs in the Image➪ Adjust sub- menu or, better yet, on the cutting room floor. ✦ Tiles: This filter breaks an image up into a bunch of regularly sized but ran- domly spaced rectangular tiles. You specify how many tiles fit across the width and height of the image — a value of 10, for example, creates 100 tiles—and the maximum distance each tile can shift. You can fill the gaps between tiles with foreground color, background color, or an inverted or normal version of the original image. A highly intrusive and not particularly stimulating effect. ✦ Extrude: The more capable cousin of the Tiles filter, Extrude breaks an image into tiles and forces them toward the viewer in three-dimensional space. The Pyramid option is a lot of fun, devolving an image into a collection of spikes. Tip 6 Photoshop 6 [...]... in Chapter 7 And finally, for complete information on the Custom and Displace filters, crack open Chapter A on the CD-ROM at the back of this book As for the other filters in the Filter ➪ Distort, Pixelate, Render, and Stylize submenus, stay tuned to this chapter to discover all the latest and greatest details Third-party filters In addition to using the filters provided by Photoshop, you can purchase... dramatically affects the performance of the filter For example, if you apply Mezzotint in the Lab mode, you again whittle the colors down to eight, but a very different eight — black, cyan, magenta, green, red, two muddy blues, and a muddy rose — as shown in the top-middle example of Color Plate 11-3 If you’re looking for bright happy colors, don’t apply Mezzotint in the Lab mode 495 4 96 Part III ✦ Selections,... searching for high-contrast edges (just like the Sharpen Edge and High Pass filters), highlighting the edges with black or white pixels, and then coloring the low-contrast portions with medium gray When you choose Filter ➪ Stylize ➪ Emboss, Photoshop displays the Emboss dialog box shown in Figure 11 -6 The dialog box offers three options: ✦ Angle: The value in this option box determines the angle at which Photoshop. .. Mask dialog box You should therefore set the value according to the resolution of your image — 1 for 150 ppi, 2 for 300 ppi, and so on 499 500 Part III ✦ Selections, Masks, and Filters 1, 50% 3, 50% 5, 50% 1, 200% 3, 200% 5, 200% 1, 500% 3, 500% 5, 500% Figure 11-8: Examples of different Height settings (first value) and Amount settings (second value) The Angle value used for each image was 135 degrees... Distortion Filters For the most part, commands in the Distort submenu are related by the fact that they move colors in an image to achieve unusual stretching, swirling, and vibrating effects They’re rather like the transformation commands from the Layer menu in that they perform their magic by relocating and interpolating colors rather than by altering brightness and color values 505 5 06 Part III ✦ Selections,... textures to the image Texturizer provides access to several scalable textures and permits you to load your own (as long as the pattern is saved in the Photoshop format), as demonstrated in Figure 11-1 The one dud is Stained Glass, which creates polygon tiles like Photoshop s own Crystallize filter, only with black lines around the tiles 489 490 Part III ✦ Selections, Masks, and Filters Burlap Canvas Sandstone... filters from other companies In fact, Photoshop supports its own flourishing cottage industry of third-party solutions from wonderful companies such as Extensis, Alien Skin, Andromeda, and others 491 492 Part III ✦ Selections, Masks, and Filters CrossReference The CD-ROM at the back of this book includes sample versions of some of my favorite filters For complete information on the specific filters and... lights the image in relief For example, if you enter a value of 90 degrees, you light the relief from the bottom straight upward The white pixels therefore appear on the bottom sides of the edges, and the black pixels appear on the top sides Figure 11-7 shows eight reliefs lit from different angles I positioned the images so that they appear lit from a single source Figure 11 -6: The Emboss dialog box... deliver the most successful results (For a preview of these effects, sneak a peek at Figure 11-2.) The following steps explain how to create a Crystal Halo, using the images in Figures 11-2 and 11-3 as an example STEPS: Creating the Crystal Halo Effect 1 Select the foreground element around which you want to create the halo Then choose Select ➪ Inverse to deselect the foreground element and select the... Other ➪ Minimum As I explained in Chapter 10, this filter enables you to increase the size of the deselected area around the foreground element The size of the Radius value depends on the size of the halo you want to create I entered 15 because I wanted a 15-pixel halo (Photoshop 6 no longer limits the Radius value to a measly 10 pixels; you can now enter values as high as 100.) 4 Choose Filter ➪ Blur . uncompressed images in the TIFF format. But as with all good things in life, it will take a while for those options to be available in moderately priced equipment. 6 Photoshop 6 480 Part III ✦ Selections,. ultimately a novelty that takes about a year and a half to apply. 6 Photoshop 6 11 11 CHAPTER ✦✦✦✦ In This Chapter Capsule descriptions of Photoshop s special effects filters Clever ways to use the Pixelate. image into tiles and forces them toward the viewer in three-dimensional space. The Pyramid option is a lot of fun, devolving an image into a collection of spikes. Tip 6 Photoshop 6 489 Chapter 11