Photoshop cs5 cho nhiếp ảnh gia part 58 pptx

359 ■ FILTERS Blurs Photoshop CS5 has an impressively long list of blurs, but we’ll cover only the ones that are particularly applicable to nature photographs. We find that Gaussian blurs, and occasionally lens blurs, are the main ones we use. You may want to explore other blurs, such as smart blurs, motion blurs, and zoom blurs as well. Gaussian Blurs Gaussian blurs produce a hazy effect and blur the image by an adjustable amount. They’re quite useful when you want to blur a section of your image. However, it’s important to remember that if you make a selection of the area you want to blur, a Gaussian blur considers that selection a general guideline, but not an absolute man- date, for the boundaries of the blur. This transition area between blurred and not blurred sections is more apparent the more blur you apply. At times it can create a glow around your subject, as it does in the photo in Figure 9.14. Figure 9.14 Although the background was selected when the Gaussian blur was applied, it included some of the pink from the spoonbill, resulting in a pleasant glow around the bird. Ph oto by EllE n Anon To apply a Gaussian blur, take the following steps: 1. Make a copy of your Background layer and convert the layer for a Smart Filter by choosing Filter > Convert for Smart Filter. 2. You may choose to first select the area to apply the blur to using any of the selection tools, or you may prefer to rely completely on painting a layer mask. 607343c09.indd 359 4/11/10 11:07:42 PM 360 c h a p t e r 9: CREATIVE EFFECTS ■ 3. Apply the blur to the copy layer by choosing Filter > Blur > Gaussian Blur. Using the preview as a guide, set the radius to determine how much blur you want. By using a Smart Filter, you can tweak the amount of blur at a later time if necessary. If you have made a selection first, the mask will reflect that selection. If you prefer to rely on a layer mask, it will be easier to begin by filling the filter mask with black by clicking on the mask and going to Edit > Fill > Use Black. Then make sure white is your foreground color in the Color Picker and paint the areas you want to appear as blurred. Using a reduced opacity with the brush will partially blur areas. Lens Blur The Lens Blur filter mimics the appearance of a reduced depth of field so that your subject remains in focus while the background fades away. With this filter, you specify part of the image as your subject that you want to remain in sharp focus and then set it to progressively blur other areas. You can also control the creation and appearance of specular highlights. Note: Although the Lens Blur filter can be helpful at times, it’s still more efficient to use the cor- rect aperture setting in the field. 1. Duplicate the Background layer (by dragging it to the Create a New Layer icon in the Layers panel). The key to the Lens Blur filter is creating a depth map. Don’t let the name intimidate you. This is where you define what parts of the image you want sharp and what parts to blur, as well as how much blur you want to add. The depth map is essentially a layer mask. There are two ways to create a depth map; one way is to use an alpha channel, and the other is to use a selection. The easiest way, and one that works well with scenics, is to create it from an alpha channel. Figure 9.15 shows an image in which the Lens Blur filter is being used to blur the trees in the background. An alpha channel with a gradient was created to tell the filter which parts of the image to keep sharp and which parts to blur. Note: An alpha channel is an additional channel located in Channels that stores any selections you’ve saved. In alpha channels, selected pixels are white, unselected pixels are black, and partially selected pixels are a shade of gray. 607343c09.indd 360 4/11/10 11:07:42 PM 361 ■ FILTERS Figure 9.15 The Lens Blur lter was used to blur the trees in the background. The depth map was based on a gradient on an alpha channel. Ph o to by EllEn An o n 2. To create a depth map based on a selection, skip to Step 3. To create a depth map using an alpha channel, follow these steps: a. Open the Channels panel, and create a new alpha channel by clicking the Create New Channel icon . Your preview becomes entirely black. b. Select the Gradient tool from the Tools panel. The gradient is used to define a gradual transition from black to white so that the blur tapers off gradually. c. On the tool Options bar, open the Gradient picker (click the arrow next to the first field), and then click the third option in the drop-down panel (see Figure 9.16). This produces a gradient from black to white. Set the gradient type to Linear by clicking the first icon to the right of the Gradient picker in the Options bar. Figure 9.16 Choose the black- to-white gradient to use as the basis of your depth map. 607343c09.indd 361 4/11/10 11:07:42 PM 362 c h a p t e r 9: CREATIVE EFFECTS ■ Note: You can use any style of gradient that works for your particular image. For example, a radial gradient may be effective if you want to have everything blur around your subject. d. After you apply the blur, wherever the gradient is black, the image will be sharp; where the gradient is white, the image will be blurred. So if you begin near the bottom of your image and drag the gradient toward the top, the blur affects the top of your image but not the bottom. Note that you can create this gradient anywhere in your image or invert it if desired. Later—in the Lens Blur Filter dialog box—you can also refine where it begins. e. Your alpha channel is now ready, containing the gradient that determines where the blur is strongest and weakest. Click the RGB channel, and then return to the Background copy layer in the Layers panel. Skip to Step 4. 3. An alternate approach to creating the depth map is to create a selection first and use this selection as the basis for the depth map. This approach is fre- quently useful with a discrete subject such as an animal or bird that you want to separate from the background: a. Create a selection using any of the selection methods to define the area you want to blur. b. Save the selection by choosing Select > Save Selection. Do not feather the selection. c. In the Save Selection dialog box (shown in Figure 9.17), do the following: Figure 9.17 Save your selection with an easily recognizable name as a new channel. i. Leave the channel set to New. ii. Enter a name that will allow you to easily recognize your selection. In this example, we used “whitepeacock.” iii. Under Operation, leave New Channel selected. iv. Click OK. d. Deselect the selection by choosing Select > Deselect. e. To feather the selection, go to the Channels panel, and click the channel you saved to make it visible. It appears as a black-and-white version of your image. f. Choose Blur > Gaussian Blur, and using your mask as a preview, determine how soft the edge of the mask should be. g. Click the RGB channel, and return to your Background copy. 607343c09.indd 362 4/11/10 11:07:43 PM 363 ■ FILTERS 4. Now, regardless of how you created your blur depth map, choose Filter > Blur > Lens Blur. 5. At the right of the Lens Blur dialog box, under Depth Map, set the source for the depth map to Alpha Channel 1 (shown in Figure 9.18) or to the selection, depending on which method you have followed. Figure 9.18 Choose the alpha channel to use as the basis for your depth map (if you created a depth map using a gradient on an alpha channel) or the name of the selection (if you made a selection to serve as the basis of the map). 6. Set the preview to Faster initially to generate previews to help you select your settings. Then change it to More Accurate when you have made your final choices to preview the effect. 7. The Blur Focal Distance slider allows you to fine-tune where the blur begins. (It’s similar to setting your camera at a certain focal distance.) To use it, click the part of the image you want to remain sharp. Photoshop sets the Blur Focal Distance automatically for you. 8. Drag the Radius slider to define how much blur to add, checking the preview (see Figure 9.19). Figure 9.19 Preview the amount and placement of the blur. Note that this image uses a saved selection in the alpha channel as the basis of the depth map. Ph o to by EllEn An o n 607343c09.indd 363 4/11/10 11:07:43 PM 364 c h a p t e r 9: CREATIVE EFFECTS ■ 9. Once you’ve set your Source and Blur Focal Distance settings, adjust the other options to get the look you want, using the preview to see how the settings interact: T• he Iris settings allow you to specify the shape and size of specular highlights. Some readers will appreciate the fine control this offers, while others may prefer to use the default settings. If your image doesn’t have any specular highlights, then don’t worry about setting the Iris values. T• he Specular Highlights settings enable you to determine which values should be used as specular highlights. The Brightness setting allows you to specify how bright to make the specular highlights, while the Thresh- old setting specifies which values are to be used as specular highlights. (You can choose from 0 to 255.) True specular highlights should have a value of 255, but you may want to create specular highlights by using a slightly lower setting. Many images have no specular highlights. Some people choose to add some noise to simulate the appearance of film grain. If you choose to add noise, check the box to make it monochromatic. (Adding color noise will look like digital noise, which we try to eliminate!) Usually the Gaussian distribution appears more natural than uniform. 10. When you are satisfied with your settings, click OK to perform the blur. 11. If you find that you blurred areas you didn’t intend to, you can modify them by adding a layer mask to your blurred image layer. Use as soft a brush as possible on the layer mask. Note: To reduce the effect of any filter immediately after applying it, choose Edit > Fade, and reduce the effect by adjusting the slider. This option exists only immediately after applying the filter. The Liquify Filter The Liquify filter can be a lot of fun. It’s like finger-painting with the pixels but with much more control and much cleaner hands! You can stretch, push, pull, pucker, or bloat any area to create subtle or dramatic distortions. When working with people, the Liquify filter can be used to create digital plastic surgery, nipping and tucking and enhancing the person’s contours. With nature photography, the effects are often more creative and less realistic. This is one of our favorite filters to use to create artistic effects with flowers (see Figure 9.20). 607343c09.indd 364 4/11/10 11:07:43 PM 365 ■ FILTERS Figure 9.20 Using the Liquify lter transforms a bland picture of orchids into a striking ne-art image. Liquify can be used with 16-bit or 8-bit images, but not on a Smart Object layer. Unfortunately, it’s not available as a Smart Filter. To use the Liquify filter, cre- ate a Stamp Visible layer by clicking on the top layer. Hold down the Alt/Option key and continue to hold it while choosing Layers > Merge Visible. Don’t release the Alt/ Option key until you see the new layer appear on top of the others. (If all the layers disappear, you released the Alt/Option key too soon!) Be aware that unless you have a fast computer with a lot of memory, process- ing the Liquify effects may be slow. For that reason, you may want to convert a copy of your image to 8-bit and use the filter on that version. Once you have established effective settings for your image, you can save them and then apply them to a 16-bit version if you prefer. Don’t forget to work on a copy of your Background layer or the Stamp Visible layer, both for safety and so you can apply a layer mask or reduce the opacity of the layer. Perhaps more than any other filter in Photoshop, this is one you have to play with to use effectively. Let’s look at the Liquify dialog box, which you open by choos- ing Filter > Liquify. A variety of tools appear in the toolbox column on the left, as shown in Figure 9.21. Some of these tools apply the distortions, while others, such as the Freeze tool, enable you to apply a quick mask to certain areas to “freeze” the effects. The Hand and Zoom tools work as usual. The primary tool we tend to use is the Warp tool, although it’s worth experimenting with the others. 607343c09.indd 365 4/11/10 11:07:44 PM 366 c h a p t e r 9: CREATIVE EFFECTS ■ Forward Warp tool Reconstruct tool Twirl Clockwise (Alt/Option-click to Pucker tool Bloat tool Push Left tool Mirror tool Turbulence Freeze Mask Thaw Mask Hand tool Zoom tool twirl counterclockwise) Figure 9.21 The Liquify dialog box oers several tools. On the right side of the Liquify dialog box (shown in Figure 9.22) are options for using the tools: Figure 9.22 On the right side of the Liquify dialog box are the controls for the various tools. Brush Size Is as expected; it refers to the size of the brush and can be controlled by the bracket keys on your keyboard or via the setting in the dialog box. Brush Density Controls how the brush is feathered at the edges. The effect is strongest in the center of the brush and lighter at the edges. Brush Pressure Controls how quickly the distortions are applied when you drag a tool across your preview image. Using too large a pressure may make it difficult to stop exactly where you want. Brush Rate Controls how quickly distortions are applied when you use a tool that can be held stationary, such as bloat or twirl. Turbulent Jitter Sets how tightly the Turbulence tool scrambles the pixels. 607343c09.indd 366 4/11/10 11:07:45 PM 367 ■ FILT ER S Reconstruct Mode Offers additional choices for ways to reconstruct the image. Some are similar to those offered in the Reconstruction Options section, while others are in addition to those options. If you just want to return to the original state, choose Revert. The other options create further distortions. Reconstruct Options T hese options allow you, with the Reconstruct tool selected, to spec- ify a mode for the reconstruction, which can either create further distortions or revert to the original image. When you have achieved the desired effect, if you’re working on a full- resolution image, you can simply click OK to apply your work to the picture. If you are using a small-file version of your image as we suggested at the start of this section, click Save Mesh. Another dialog box appears in which you can name the effect and specify where to save it (see Figure 9.23). Figure 9.23 After you are satised with the eect, save the mesh to apply to your full-sized le. Once the mesh is saved, open your full-sized file, choose Filter > Liquify, and click Load Mesh. Choose the mesh you just saved, and click OK to perform the distor- tion. If you are feeling adventurous, apply a saved mesh to an unrelated image—some- times serendipity comes into play, and you create something unexpected but wonderful! For Photoshop Elements Users: Liquify The Elements Liquify filter is quite similar to the one in Photoshop. Access it from Filter > Dis- tort > Liquify. The Elements version lacks Freeze and Thaw tools, but has specific tools for Twirl Counterclockwise and Reflection. Elements does not have options for Brush Density, Brush Rate, or Reconstruction. In addition, you cannot save the mesh to apply on other images. Try It! Open the image called Liquify from this book’s companion website, www.sybex .com/go/photoshopnature , or open one of your own images, and see what you can create with it. Be sure to vary the settings and tools to get different effects. Using the Filter Gallery Recent versions of Photoshop (CS and newer, as well as Elements) contain a filter gal- lery (Filter > Filter Gallery) rather than just a simple list of individual filters. This gallery enables you to preview the effects of a variety of filters, as well as to preview the effects For Photoshop Elements Users: Liquify The Elements Liquify filter is quite similar to the one in Photoshop. Access it from Filter > Dis - tort > Liquify. The Elements version lacks Freeze and Thaw tools, but has specific tools for Twirl Counterclockwise and Reflection. Elements does not have options for Brush Density, Brush Rate, or Reconstruction. In addition, you cannot save the mesh to apply on other images. 607343c09.indd 367 4/11/10 11:07:45 PM . 359 ■ FILTERS Blurs Photoshop CS5 has an impressively long list of blurs, but we’ll cover only the ones that are particularly applicable to nature photographs. We. your Background layer and convert the layer for a Smart Filter by choosing Filter > Convert for Smart Filter. 2. You may choose to first select the area to apply the blur to using any of. depth map. Don’t let the name intimidate you. This is where you define what parts of the image you want sharp and what parts to blur, as well as how much blur you want to add. The depth map is