Tài liệu Photoshop cs5 by Dayley part 64 pot

Part IV: Enhancing, Correcting, and Retouching 448 FIGURE 14.10 The Smart Sharpen filter allows you to fine-tune the filter to set the amount of sharpening that takes place in the highlights range. Using Blur Filters to Soften Images Blurring applies the opposite effect to images that Sharpening does. Instead of finding edges and adding contrast, blurring reduces the contrast, making edges softer. Photoshop has 11 Blur filters. Caution Blurring images is done by smoothing out some of the details. The detail is permanently lost. You likely want to apply the blurring filters on a separate duplicate layer to avoid data loss problems. n Each Blur filter reduces the contrast at different levels and in different ways. If you choose a Gaussian Blur, for example, each pixel is compared to pixels around it in an even radius, and pix- els that are closer receive higher weight than pixels that are farther away. Choosing the Blur filter softens the edges in your image by blurring only those pixels that are in high contrast areas .If you choose a Box Blur, each pixel is compared to pixels around it in a box shape, giving the end result an edgier appearance. If you really want an interesting result, choose a Shape Blur, where you can choose from dozens of shapes to use for the pixel comparison. Automatic Blur filters The first three Blur filters on the Filter ➪ Blur menu are automatic Blur filters, meaning that they don’t require any input from the user. These filters are Average, Blur, and Blur More. 21_584743-ch14.indd 44821_584743-ch14.indd 448 5/3/10 10:35 AM5/3/10 10:35 AM Chapter 14: Sharpness, Blur, and Noise Adjustments 449 l Average: Takes the average color of the frame (or selected area) and fills the entire frame with that color. It’s not a great photo enhancer, but it could be useful for creating match- ing backgrounds when placing odd-sized photos in a video file. l Blur: Automatically smoothes the color transitions in an image to soften the edges. l Blur More: Works the same as the Blur filter by smoothing the color transitions in an image to soften the edges. The Blur More filter is three or four times stronger than the Blur filter, although it is still very subtle. Shape Blur filters The Gaussian Blur, Box Blur, and Shape Blur filters blur all the pixels throughout an image or selection rather than selected pixels in high contrast areas, as the Blur and Blur More filters do. The pixels are blurred by reducing the contrast between each pixel and surrounding pixels. The sur- rounding pixels are determined by which one of these filters you use and the Radius setting. Gaussian Blur The Gaussian Blur compares the pixels in an even radius around each pixel and applies a weighted aver- age to each pixel to reduce its contrast to the surrounding pixels. Its effects are a general softening of the image. You can apply a Gaussian Blur filter by choosing Filter ➪ Blur ➪ Gaussian Blur to open a dialog box that allows you to set the radius of the blur. The radius, of course, is the number of pixels around each pixel that it is compared to. Figure 14.11 shows the effect of creating a selection around the subject and then applying a Gaussian Blur filter. Notice that the Gaussian Blur is a very smooth blur. FIGURE 14.11 A Gaussian Blur has been liberally applied to the background to clearly demonstrate the effect. Box Blur A Box Blur compares the pixels in a box shape rather than the feathering out comparison of the Gaussian Blur. The result is a blur with edges. The Box Blur can be applied by choosing Filter ➪ Blur ➪ Box Blur. This filter has the same dialog box as the Gaussian Blur, consisting of a preview 21_584743-ch14.indd 44921_584743-ch14.indd 449 5/3/10 10:35 AM5/3/10 10:35 AM Part IV: Enhancing, Correcting, and Retouching 450 window and a Radius setting, as shown in Figure 14.12. With the Radius setting turned up to 80, you can clearly see the difference in the blur filters. Figure 14.12 also illustrates one of the down sides to the Box Blur. Notice that the area around the boy and in particular between the boy’s arm and his body is not very blurred. This is because of the radius setting. The larger the radius setting, the less bluring that occurs around the edges of the selection or mask. FIGURE 14.12 The Box Blur gives the background an edgy look. Shape Blur As if having a soft blur or an edgy blur weren’t enough, Photoshop gives you the choice of literally dozens of shapes to use when comparing pixels. This works in just the same way as the Gaussian Blur and Box Blur, except the pixels are compared to one another in the shape chosen. Maybe someone at Adobe had too much time on his hands, but the result can create some very interesting blur effects. Open the Shape Blur dialog box by choosing Filter ➪ Blur ➪ Shape Blur. You can see in Figure 14.13 that the dialog box is full of all sorts of fun shapes you can use in the Blur filter. Click the triangle next to the list of shapes to choose from a menu of all the shapes available. Of course, the preview window and the Radius setting are part of the dialog box as well. The higher you set the Radius setting, the more likely you are to see a real difference in the effects created by each shape. Figure 14.13 is an example of what the arrow shape does for this blur effect. On the Web Site The project file used to create the image shown in Figures 14.11, 14.12, and 14.13 can be found on this book‘s Web site as Figure 14-11.psd. You can open it in Photoshop to see the effects of the Blur filters. Each of the Gaussian, box, and shape filters is in its own Smart Object layer, so you can turn the blurs on and off to see the different effects. n 21_584743-ch14.indd 45021_584743-ch14.indd 450 5/3/10 10:35 AM5/3/10 10:35 AM Chapter 14: Sharpness, Blur, and Noise Adjustments 451 FIGURE 14.13 The Shape Blur, with a radius of 200 just like the previous examples, has a completely different look than either the Gaussian Blur or the Box Blur. Direction Blur filters The Motion Blur and Radial Blur filters create the illusion of motion in your image. These filters are very useful in adding a motion effect either to the entire image or a specific selection. A Motion Blur adds directional blur that moves across the 2D plane of the image. A Radial Blur adds blurring that radiates outward from a central point in the image. Adding a Motion Blur to an image The Motion Blur simulates movement in a straight path, determined by setting the angle in the dialog box. The following example takes you through the process of adding a Motion Blur to an image: 1. Open the image in Photoshop. 2. Select the area of the image where you want to add the Motion Blur, and use Ctrl (Ô) + C to copy the selection to the clipboard. 3. Add a new layer to the image using the Layers menu. 4. Paste the contents of the clipboard into the newly created layer, as shown in Figure 14.14. 5. Right-click the new layer, and select Convert to Smart Object. 6. Select Filter ➪ Blur ➪ Motion Blur from the main menu to apply a Motion Blur filter to the Smart Object. The Motion Blur dialog box is displayed, as shown in Figure 14.15. 21_584743-ch14.indd 45121_584743-ch14.indd 451 5/3/10 10:35 AM5/3/10 10:35 AM Part IV: Enhancing, Correcting, and Retouching 452 FIGURE 14.14 Paste the clipboard contents into the new layer. FIGURE 14.15 The Motion Blur filter allows you to set the angle and direction of the blur that is applied to the image. 7. Adjust the Angle to match the relative direction of the motion you want in the image. In the example, we adjusted the angle to 10 to match the slope of the field. 21_584743-ch14.indd 45221_584743-ch14.indd 452 5/3/10 10:35 AM5/3/10 10:35 AM Chapter 14: Sharpness, Blur, and Noise Adjustments 453 8. Adjust the Distance to the desired number of pixels. A small number of pixels blurs the image only slightly. Adjusting the Distance up a larger amount increases the amount of movement in the subject and makes the image more blurry. In the example, we increased the distance to 50 to make the runner look like he’s moving faster. 9. Click the OK button to apply the Motion Blur filter to the image. In the final image in Figure 14.16, notice that the runner now looks like he’s moving quickly while the background remains stationary. FIGURE 14.16 Adding a Motion Blur filter to an image can give the appearance that an object is in motion or, in this case, in faster motion than the original image. On the Web Site The project file used to create the image shown in Figure 14.16 can be found on this book’s Web site as Figure 14-16.psd. You can open it in Photoshop to see the effects of the Motion Blur filter. n Radial Blur The Radial Blur filter allows you to add blurs that radiate outward from a center point. To apply a Radial Blur, select Filter ➪ Blur ➪ Radial Blur from the main menu and set the following options, as shown in Figure 14.17: l Amount: Specifies the amount of blur to apply to the layer. l Spin: Gives the image the illusion that it is spinning in a circular motion. l Zoom: Blurs the edges of the image a greater amount than the center, creating the illusion that the image is moving rapidly toward or away from the viewer. 21_584743-ch14.indd 45321_584743-ch14.indd 453 5/3/10 10:35 AM5/3/10 10:35 AM Part IV: Enhancing, Correcting, and Retouching 454 l Quality: Allows you to specify either Draft, Good, or Best. The better the quality, the bet- ter the results look; however, the Radial Blur filter takes lots of processing power, so you should try it out in Draft mode first and then increase the quality after you get the desired results. l Blur Center: Allows you to drag the center of the blur to any location in the image. The lines show the amount of blurring that will take place. FIGURE 14.17 The Radial Blur has several possibilities with the Spin and Zoom options available. On the Web Site The project file used to create the image shown in Figure 14.17 can be found on this book’s Web site as Figure 14-17.psd. You can open it in Photoshop to see the effects of the Radial Blur filter and play around with the direction and amount of the blur. n Surface Blur The Surface Blur filter is the opposite of the Blur and Blur More filters. Rather than softening the edges, the Surface Blur works by softening the midtones, leaving the edges sharp and crisp. This is perfect for smoothing out slight imperfections or noise in an image without losing the crispness of the file. Smart Blur The Smart Blur allows you to blur with more precision using radius and threshold settings that allow you to specify the number of pixels involved and what the difference in the pixels should be before the filter is applied to them. To apply a Smart Blur, select Filter ➪ Blur ➪ Smart Blur from the main menu and set the following options, as shown in Figure 14.18: l Radius: Specifies the area of pixels searched to determine whether a pixel is dissimilar to its neighbors and should be blurred. l Threshold: Specifies the amount of dissimilarity a pixel must have with its neighbors before it is considered dissimilar. 21_584743-ch14.indd 45421_584743-ch14.indd 454 5/3/10 10:35 AM5/3/10 10:35 AM . adding contrast, blurring reduces the contrast, making edges softer. Photoshop has 11 Blur filters. Caution Blurring images is done by smoothing out some of the details. The detail is permanently. More filters do. The pixels are blurred by reducing the contrast between each pixel and surrounding pixels. The sur- rounding pixels are determined by which one of these filters you use and. the Radius setting are part of the dialog box as well. The higher you set the Radius setting, the more likely you are to see a real difference in the effects created by each shape. Figure 14.13