Photoshop cs5 cho nhiếp ảnh gia part 49 pps

299 ■ COMPOSITES 8 Ph o to b y Josh An o n Composites Many nature photographers are initially loath to consider making composites, believing that this is somehow “cheating” or “dishonest.” There is a clear need for photographers using Photoshop to be ethical and reveal when they have made changes to their images so that they no longer reflect the reality of what they saw and what existed. However, sometimes combining several images or elements from several pictures can create more impact and be more representative of an experience. Ironically, compositing techniques can actually enable photographers to more accurately and realistically depict what they saw in certain circumstances, such as with a panorama, an exposure composite, or a focus composite. Chapter Contents Creating Panoramas Expanding Dynamic Range Extending Depth of Field Combining Elements from Multiple Pictures 607343c08.indd 299 4/11/10 11:06:29 PM 300 c h a p t e r 8: COMPOSITES ■ Creating Panoramas The advent of the digital darkroom freed photographers from being tied to the con- straints of any one particular camera format, whether it is 35mm, medium format, or some other format. By using Photoshop or other software programs, you can stitch together a series of images to create a photograph of a particular shape that bet- ter suits the subject. An added benefit of stitching together several frames is that the larger file you create enables you to make prints that are substantially larger and more detailed than you could if you simply used a wider lens and cropped a single frame. Note: When photographing images to be combined into panoramas, using certain techniques while shooting enables you to stitch the images together with a minimum of headaches. Please refer to this book’s companion website, www.sybex.com/go/photoshopnature, for details on those techniques. Photomerge Photomerge makes it easy to stitch even 16-bit panoramas together. Photomerge automatically arranges and blends multiple images to create a panorama with just a few instructions from you. This is a tremendous time-saver and eliminates tediously stitching the images together manually as we did in versions of Photoshop prior to CS3. Since Photomerge can save the file in layers, we still have the option to tweak the image alignment when necessary, but Photomerge often does a surprisingly accu- rate job. There are two ways to get started with Photomerge: T• he easiest way to begin is to highlight the images you wish to use in Bridge— by holding the Ctrl/F key and clicking the images—and then choose Tools > Photoshop > Photomerge from Bridge’s menu. If these images are raw files, Pho- toshop automatically converts them using whatever default you have set within Adobe Camera Raw (ACR). If you have not made any changes to the default, Photoshop uses the Auto Adjust settings. I• f you prefer, select the images to use within Photoshop by going to File > Auto- mate > Photomerge. You need to set the source to use images you have previously opened, files you specify, or a folder. Check the box to have Photomerge automatically blend the files as well as to specify the type of layout you want it to use (see Figure 8.1). Most of the time we find it helpful to use the Geometric Distortion Correction option when it’s available. If the images show any signs of vignetting, you’ll want to check the option for Vignette Removal. Photomerge then creates a lay- ered file containing all the images, properly placed with layer masks applied. 607343c08.indd 300 4/11/10 11:06:29 PM 301 ■ CREATING PANORAMAS Figure 8.1 Instruct Photoshop which images to merge by specifying to open les or folders, and check the Blend Images Together box, along with the Vignette Removal and Geometric Distortion Correction options to have Photoshop automatically create the panorama. You have the following Layout options: U• se Auto to have Photomerge determine the best approach for the layout. It will read the metadata associated with the lens used and then choose which approach to use as well as apply any necessary geometric correction. Most of the time this is the choice you will use unless there is a specific reason to use one of the other options. C• hoose Perspective to have Photomerge apply corrective perspective distortion. This can be useful with some high dynamic range (HDR) alignments and other layouts with smaller angle compositions—that is, those shot with longer lenses. C• ylindrical can be used for wide-angle compositions, including 360° composi- tions. Photoshop first projects the images onto a cylinder and then unwraps them. S• pherical is also used with wide-angle compositions, particularly if the field of view is wide both horizontally and vertically. This is often the best choice (and what Auto will choose) when the images were taken with extremely wide-angle lenses, including fish-eye lenses. With fish-eyes and extreme wide-angle lenses, be sure to also select the option for geometric correction. C• hoose Reposition to have Photomerge create a canvas and align the images with no distortion applied. C• ollage is similar to Reposition but enables you to uniformly scale and rotate the images while arranging them. When Auto applies too much correction for our tastes, we often use Collage. 607343c08.indd 301 4/11/10 11:06:29 PM 302 c h a p te r 8: COMPOSI T E S ■ The panorama results will vary depending on the layout you choose, as shown in Figure 8.2. If you have Photomerge apply a distortion in the layout, the processing time increases, particularly if you’re creating a panorama from numerous large 16-bit files. However, while you’re waiting for your computer to generate the panorama, remind yourself it’s a lot faster than doing it manually! Reposition only Using Auto Figure 8.2 Using some of the layouts applies distortion, particularly at the edges of the panorama. Notice the dierence between an image that was repositioned only and one where Auto was used. Usually Photomerge does a good job, but occasionally it fails. It’s a good idea to zoom in to ensure that Photomerge has done a good job of aligning each segment. If necessary, select a layer and use the Move tool to nudge a layer into place. Of course, moving one layer will make it likely that you’ll need to move the other layers as well. Note: If you are dealing with a difficult group of files to align and blend because an object, person, or animal significantly changed position between frames, it’s best to open the files in Photo- shop, apply a layer mask to block out the object wherever necessary, and then invoke Photomerge. Photomerge will respect the layer mask and know which frame should contain the moving thing. Otherwise, Photomerge may or may not do a good job with the alignment and blending. For Photoshop Elements Users: Using Photomerge To create a new panorama in Elements from Bridge, select your images just as you would in Photoshop CS5 but choose Tools > Photoshop Elements > Photomerge Panorama. If you are using Windows, select your images in the Organizer and choose File > New > Photomerge Panorama. To select the images from within Elements, first choose File > New > Photomerge Panorama. Use the Add Open Files button to add images that are currently opened in the Project Bin to the panorama, or click Browse to browse for your images. Within the Photomerge panel, there is no Advanced Blending option in Elements. For Photoshop Elements Users: Using Photomerge To create a new panorama in Elements from Bridge, select your images just as you would in Photoshop CS5 but choose Tools > Photoshop Elements > Photomerge Panorama. If you are using Windows, select your images in the Organizer and choose File > New > Photomerge Panorama. To select the images from within Elements, first choose File > New > Photomerge Panorama. Use the Add Open Files button to add images that are currently opened in the Project Bin to the panorama, or click Browse to browse for your images. Within the Photomerge panel, there is no Advanced Blending option in Elements. 607343c08.indd 302 4/11/10 11:06:35 PM 303 ■ CR E ATI N G PANOR A M A S Advanced Image Stitching In CS5 there is another way to stitch images together that can be useful with some tricky images, including HDR panoramas. To begin, in Photoshop choose File > Scripts > Load Files into Stack or in Bridge select the files, then go to Tools Photoshop > Load Files into Photoshop Layers. A dialog box appears in which you specify which images to stack. Photoshop will cre- ate a new file containing each image as a layer. Select all the layers, and then choose Edit > Auto-Align Layers. Locking a layer will set it as the center for any distortions. A dialog box appears in which you choose the layout; it’s similar to the Photomerge dialog box discussed earlier. This places each file into the correct alignment on a correctly sized new canvas. You can apply any type of distortion or transformation necessary to each layer, as well as apply layer masks to instruct Photoshop to remove part of a layer from the final composite. The last step is to choose Edit > Auto-Blend Layers to seamlessly blend the colors and exposures. We’ll discuss using the Extended Depth of Field option later in this chapter, but when creating a panorama, you would choose the Panorama option. In this step Photoshop adds layer masks that you can tweak, although the specific adjustments used in the blending are not available. Try It! Open the Pano1a, Pano1b, and Pano1c images on the companion website, www.sybex .com/go/photoshopnature , and practice stitching them together. If you prefer, use a series of your own images. We recommend starting with a panorama of no more than three or four sections. Matching the Exposures of Each Segment of the Panorama With earlier versions of Photoshop, we often had to manually create and blend our panoramas. This is rarely necessary now that the Auto-Align and Auto-Blend algo- rithms are so good in CS5, but it’s conceivable you might shoot a series of images that Photoshop can’t blend perfectly. We’ve seen this primarily in panoramas, including the sun at sunrise or sunset with auto white balance, as shown in Figure 8.3, or if a cloud suddenly obscured the sun in the midst of a series of manual exposures for a pan- orama that were calculated when the sun was shining. Figure 8.3 Unless you manually set the white balance and exposure for your panoramas, you’re likely to get some variation in colors and tonalities between the les. Advanced Image Stitching In CS5 there is another way to stitch images together that can be useful with some tricky images, including HDR panoramas. To begin, in Photoshop choose File > Scripts > Load Files into Stack or in Bridge select the files, then go to Tools Photoshop > Load Files into Photoshop Layers. A dialog box appears in which you specify which images to stack. Photoshop will cre - ate a new file containing each image as a layer. Select all the layers, and then choose Edit > Auto - Align Layers. Locking a layer will set it as the center for any distortions. A dialog box appears in which you choose the layout; it’s similar to the Photomerge dialog box discussed earlier. This places each file into the correct alignment on a correctly sized new canvas. You can apply any type of distortion or transformation necessary to each layer, as well as apply layer masks to instruct Photoshop to remove part of a layer from the final composite. The last step is to choose Edit > Auto - Blend Layers to seamlessly blend the colors and exposures. We’ll discuss using the Extended Depth of Field option later in this chapter, but when creating a panorama, you would choose the Panorama option. In this step Photoshop adds layer masks that you can tweak, although the specific adjustments used in the blending are not available. 607343c08.indd 303 4/11/10 11:06:36 PM 304 c h a p t e r 8: COMPOSITES ■ If you discover that the exposures of the various segments of the panorama do not match, follow these steps: 1. Click the layer containing the second segment of the panorama to make it active. 2. Zoom in to magnify the area where the first segment and the second segment overlap and where the differences in exposure are evident. 3. Click the Channels panel. 4. Select the Red channel by clicking the word Red. When viewed in grayscale, the differences between the two layers are usually easy to see, as shown in Figure 8.4. Figure 8.4 Viewing the overlapping area in each channel separately makes it much easier to see the dierences. 5. Choose Image > Adjustments > Levels on the menu bar. Note that this is one of the few times we’ll have you working directly on the pixels. Unfortunately, when you’re working within channels, you can’t readily use adjustment layers. 6. Click the Midpoint slider, and drag it to match up the gray tones in layer 2 with those in layer 1. When they appear the same, as in Figure 8.5, click OK. Figure 8.5 Adjusting the Midpoint slider in Levels within each channel enables you to easily match exposures. 607343c08.indd 304 4/11/10 11:06:37 PM 305 ■ CR E ATI N G PANOR A M A S 7. Repeat the same process for the Green and Blue channels, one at a time. 8. Repeat these steps for each frame you need to match to another until your final image matches in color and tonalities (see Figure 8.6). Figure 8.6 The nal image has consistent color across the various segments. Occasionally, a simple linear correction (which Levels applies) can’t resolve the changes in exposure between the segments, in which case you need to use Curves rather than Levels in each channel to accurately match up the different segments. This happens more often when the quality or quantity of the lighting is changing dramati- cally. Follow the same procedure as described in this section, but use Curves instead of Levels. For Photoshop Elements Users: Matching Exposures Unfortunately, Elements does not have a Channels panel and provides no easy way to see a specific color component of an image. However, thanks to the power of Undo (as well as a pencil and paper), it is possible to work around this limitation. This is recommended for advanced Ele- ments users only. To fix exposure mismatches in Elements panoramas, perform the following steps: 1. Follow Steps 1 and 2 from the Photoshop instructions earlier. 2. Select the first layer that is mismatched in the Layers panel and choose Enhance > Convert to Black and White. 3. In the Adjustment Intensity sliders, set the value for the channel you wish to see, such as Red, to 100, and set the other sliders to 0. Be careful with this step because the only way to see the current slider value is to hold the mouse over the slider knob and wait for the tooltip to appear; there is no way to see the value while moving the slider knob. The result will look similar to the image shown on the following page. Continues For Photoshop Elements Users: Matching Exposures Unfortunately, Elements does not have a Channels panel and provides no easy way to see a specific color component of an image. However, thanks to the power of Undo (as well as a pencil and paper), it is possible to work around this limitation. This is recommended for advanced Ele - ments users only. To fix exposure mismatches in Elements panoramas, perform the following steps: 1. Follow Steps 1 and 2 from the Photoshop instructions earlier. 2. Select the first layer that is mismatched in the Layers panel and choose Enhance > Convert to Black and White. 3. In the Adjustment Intensity sliders, set the value for the channel you wish to see, such as Red, to 100, and set the other sliders to 0. Be careful with this step because the only way to see the current slider value is to hold the mouse over the slider knob and wait for the tooltip to appear; there is no way to see the value while moving the slider knob. The result will look similar to the image shown on the following page. Continues If you discover that the exposures of the various segments of the panorama do not match, follow these steps: 1. Click the layer containing the second segment of the panorama to make it active. 2. Zoom in to magnify the area where the first segment and the second segment overlap and where the differences in exposure are evident. 3. Click the Channels panel. 4. Select the Red channel by clicking the word Red. When viewed in grayscale, the differences between the two layers are usually easy to see, as shown in Figure 8.4. Figure 8.4 Viewing the overlapping area in each channel separately makes it much easier to see the dierences. 5. Choose Image > Adjustments > Levels on the menu bar. Note that this is one of the few times we’ll have you working directly on the pixels. Unfortunately, when you’re working within channels, you can’t readily use adjustment layers. 6. Click the Midpoint slider, and drag it to match up the gray tones in layer 2 with those in layer 1. When they appear the same, as in Figure 8.5, click OK. Figure 8.5 Adjusting the Midpoint slider in Levels within each channel enables you to easily match exposures. 607343c08.indd 305 4/11/10 11:06:38 PM 306 c h a p t e r 8: COMPOSITES ■ For Photoshop Elements Users: Matching Exposures (Continued) 4. Repeat Step 3 for the layer you wish to match so that you are effectively looking at the Red channel in both layers. 5. Select the layer you wish to adjust, and choose Enhance > Adjust Lighting > Levels from the menu bar. 6. Change the pop-up to be the same as the channel you are working in, such as Red. 7. Click the Midpoint slider, and drag it to match up the grayer tones in layer 2 with those in layer 1. When they appear the same, as you saw in Figure 8.5, write down the value you used in the Levels dialog and click Cancel. 8. In the Undo History panel, select the step immediately before Convert to Black and White to restore your image to color. 9. Repeat Steps 3 through 8 for the Blue and Green channels. 10. With the image again in color, select the layer you wish to adjust and choose Enhance > Adjust Lighting > Levels from the menu bar. 11. Set the pop-up to each individual channel and type in the values that you wrote down in Step 7. Once finished, click OK to apply the changes. 607343c08.indd 306 4/11/10 11:06:38 PM 307 ■ CREATING PANORAMAS Joe McDonald, one of the foremost wildlife photographers, often creates com- posites. He offers the following thoughts. Composites by Joe McDonald Shooting digitally, my photography now has far fewer limitations. Think about it. The basic laws of optics normally restrict our vision, but for virtually my entire career I’ve been further limited not by what I couldn’t see, but by what my camera could capture. Limitations imposed by the depth of field or the angle of view or the exposure latitude all conspired to force me to make images not as I saw them but as I knew my medium could render them. We all lived with this and probably didn’t even think about it, for it was the reality of photography at the time. Digital has changed all of that for me: I now make images with the “reality” of the scene in mind. This can take any number of forms. Sometimes I simply have too much lens, but by shoot- ing a panorama, I still get the image size and detail I wanted while encompassing more of the habitat as well. On other occasions I’ll shoot focus composites, focusing on the foreground if it bears interest, and on the main subject so that the finished image lacks the unnatural dimen- sion typical of long-lens shots. If necessary, I’ll add some Gaussian blur to a background to draw more attention to the subject. Restrictions created by a broad exposure latitude have been signicantly reduced. Often I’ll “shoot for the middle,” knowing that I can convert a raw image twice, once biasing for the underexposure and once for the over. Usually I’ll cover myself for those shots by shooting two exposures, metering for each value. That way, if the exposure latitude was indeed too broad for a single image, I’ll have a good chance of recording the scene if I use two separate images. This has simply made my photography more fun because I’m not frustrated or stymied by past limitations. I’m free to try things, probably way more than I’ll ever have time to work with in the digital darkroom, but that’s secondary. The fun part is the shooting, and with digital, I feel I have the potential of capturing what I truly see. © Joe McDonald, www.hoothollow.com 607343c08.indd 307 4/11/10 11:06:39 PM 308 c h a p t e r 8: COMPOSITES ■ Expanding Dynamic Range Until recently, the dynamic range, or exposure latitude, that we could capture in a single image was limited by camera and film technology. Often, especially during the midday hours, there was too much contrast to be able to capture in a single shot. We had to choose to give up detail in the highlights, the shadows, or both. Photo- shop enables us to combine several images of the same subject, taken using different exposures, to retain detail in the highlights and shadows while simultaneously having the midtones properly exposed. It’s almost magical how we can create an image that reflects what we actually saw, no longer limited by the exposure latitude of film. There are two approaches that we’ll describe to extend the exposure latitude in an image. One, that we call the “Cookbook” approach, is partially manual. The other takes full advantage of the completely revised and impressive HDR tool in CS5. Although you could simply stack two images, a light one and a darker version of the same image, and use a layer mask to reveal whichever layer is better exposed, it’s rare in nature photography to encounter situations where that will be the best approach. That works only if the areas that are exposed differentially have discrete boundaries that are easy to mask. It’s better to use one of the two approaches we describe here. First we offer some hints on how best to photograph a contrasty situation so that you can easily combine the shots in Photoshop. Shooting to Expand Latitude When you encounter a situation in which there is too much contrast to capture detail in the entire scene in a single shot, take several shots at different exposure levels to combine later in Photoshop, and keep these suggestions in mind: U• se a tripod, and take your first shot, exposing for the shadow areas. Check your in-camera histogram to ensure that the shadow areas do not spike against the left side of the histogram. If they do, take another shot, adding more light to the exposure. Don’t worry about the highlights; the overall image is expected to be too light in this shot. Note: If you don’t have a tripod, try setting your camera to auto-bracket three exposures, each at least one stop different. Set your camera so that you can hold the shutter down to take the three shots as quickly as possible, without having to release the shutter button between shots, if possible. T• ake a series of shots, varying the exposure by changing the shutter speed, not the aperture (which would change the depth of field). If you use aperture prior- ity, then you simply need to dial in different exposure compensation amounts for each shot. V• ary the exposures by one to two f/stops each. Don’t try to bracket by small increments such as 1/3 to 1/2 stops. When making an HDR composite, you don’t need small differences in exposures. 607343c08.indd 308 4/11/10 11:06:39 PM . blending. For Photoshop Elements Users: Using Photomerge To create a new panorama in Elements from Bridge, select your images just as you would in Photoshop CS5 but choose Tools > Photoshop. Elements. For Photoshop Elements Users: Using Photomerge To create a new panorama in Elements from Bridge, select your images just as you would in Photoshop CS5 but choose Tools > Photoshop. S Advanced Image Stitching In CS5 there is another way to stitch images together that can be useful with some tricky images, including HDR panoramas. To begin, in Photoshop choose File > Scripts