Photoshop cs5 cho nhiếp ảnh gia part 38 doc

231 ■ EXPOSURE ADJUSTMENTS 6 Exposure Adjustments Nature photography—and all photography, for that matter—is about light and creating a proper exposure that records that light. Once you’ve captured the optimal exposure, you can use Photoshop to make the most of the information you’ve captured. As you’ve already seen, we make most of our exposure adjustments in Adobe Camera Raw (ACR). In this chapter, we’ll guide you through methods to fine-tune the exposure for your images in Photoshop, many of which are quite similar to those found in ACR, and then discuss how to limit those tonal corrections to specific parts of your image. Chapter Contents Shooting for Optimal Exposure Using the Adjustments Panel Tonal Adjustments with Levels Targeting Adjustments Using a Layer Mask Curves Creating a Virtual Split Neutral-Density Filter Safe Dodge and Burn Layers The Shadows/Highlights Adjustment Emphasizing Your Subject 607343c06.indd 231 4/12/10 11:42:38 PM 232 c h a p t e r 6: EXPOSURE ADJUSTMENTS ■ Shooting for Optimal Exposure The ability to perform exposure adjustments in imaging software leads some photog- raphers to feel they can be a little less careful during the original capture. We strongly advise you against believing that. Creating the very best images in a digital workow requires that you start with the very best quality. Therefore, focus on creating the best exposures in the field, and select only your very best exposures to work on in Photo- shop (see Figure 6.1). By ensuring that you have captured an appropriate exposure in the original capture, you’ll achieve maximum detail in the image. Your adjustments can then focus on revealing the maximum amount of detail possible and emphasizing particular areas of your image, as we’ll discuss in this chapter. Figure 6.1 Achieving optimal exposure is an important rst step for any photograph. It is especially important when you need to preserve detail in both shadow and highlight areas, such as in this scene. Ph o to by EllEn An o n 607343c06.indd 232 4/12/10 11:42:39 PM 233 ■ USING THE CS5 ADJUSTMENTS PANEL As we discussed in Chapter 3, “Adobe Camera Raw,” in Photoshop CS5 you can make most, if not all, your adjustments in ACR not only for raw files, but also for JPEGs and TIFFs. However, there are times you’ll choose to use the original tools within Photoshop. Although the exposure tools in ACR and Photoshop are very simi- lar, sometimes they differ in significant ways that will make you favor one over the other. In addition, you may want to use Photoshop to create an adjustment to apply to just one part of your image. When considering the best exposure, keep in mind Michael Reichmann’s advice back in Chapter 1, “Thinking Digitally,” to “expose to the right” in the camera. Using the CS5 Adjustments Panel In Photoshop we make adjustments using adjustment layers rather than making the adjustments directly on the pixels themselves. This is beneficial in several ways. It allows more exibility in the adjustments so that you can tweak them repeatedly if necessary. Additionally, it often results in a higher-quality image because the pixels themselves are not changed until the image is output. Before we talk about any of the specific adjustments—including the exposure adjustments as well as the color adjust- ments that we’ll cover in Chapter 7, “Color Adjustments,”—you need to understand how the Adjustments panel works. CS5 has an Adjustments panel and a Masks panel that share a panel group. You can access these directly by going to Window > Adjustments and Window > Masks. We’ll talk about the Masks panel later in the chapter. If you click the Adjustment icon at the bottom of the Layers panel the way you did in earlier versions of Photoshop, the Adjustments panel will open, set to the specific adjustment you’ve chosen. When you first view the Adjustments panel, it will appear as shown in Fig- ure 6.2. Hover your cursor over the icons to see the name of each adjustment, then click on one to access that specific adjustment. Although you can choose among spe- cific default presets, we rarely find them useful. Figure 6.2 Use the Adjustments panel to access adjustments. 607343c06.indd 233 4/12/10 11:42:39 PM 234 c h a p te r 6: E X P OS U R E A DJ UST M EN TS ■ Once you open any of the adjustments, the specific dialog will be customized according to the particular adjustment, but the icons on the bottom, as shown in Figure 6.3, are common to all the adjustments. At the left of that row of icons is an arrow . Click it to return to the main adjustment panel to choose other adjust- ments. Next is the icon, which you can click to enlarge the dialog box or return it to standard size. The icon toggles between making the adjustment layer affect all layers beneath it or just the layer immediately underneath it. Most of the time you’ll want it to affect all the layers beneath it, but occasionally it’s helpful to clip an adjust- ment to the layer immediately beneath it. The eye icon toggles the visibility of the adjustment layer. Toggling this icon is helpful so you can compare the image with and without the adjustment. Next is the icon that lets you preview the previous state. This is helpful when you’re tweaking an adjustment and want to see whether the change you just made was helpful. Click the icon to reset the adjustment to its default values. Click the trashcan icon to delete the adjustment layer entirely. Figure 6.3 Each adjustment shares common tools along the bottom of the panel. The amount of control that’s immediately accessible from within the Adjust- ments and Masks panels is impressive! We’ll give examples of how to use these new panels as we progress through this chapter. For Photoshop Elements Users: Adjustment Layers Elements users should also make their adjustments using layers rather than directly on the pixels. To access adjustment layers in Elements, click the in the Layers panel and choose the desired adjustment. This will automatically create an adjustment layer and open the Adjust- ments panel. In Elements, the Adjustments panel contains options and settings for the selected adjustment, but does not include the ability to create other adjustment layers. For Photoshop Elements Users: Adjustment Layers Elements users should also make their adjustments using layers rather than directly on the pixels. To access adjustment layers in Elements, click the in the Layers panel and choose the desired adjustment. This will automatically create an adjustment layer and open the Adjust - ments panel. In Elements, the Adjustments panel contains options and settings for the selected adjustment, but does not include the ability to create other adjustment layers. 607343c06.indd 234 4/12/10 11:42:40 PM 235 ■ TONAL ADJUSTMENTS WITH LEVELS Tonal Adjustments with Levels The Levels adjustment provides good basic control over tonal adjustments for your images, with the capability to adjust contrast by independently controlling shadows and highlights within your image, as well as to adjust the overall brightness. In ACR you can make similar adjustments by setting the Exposure, Blacks, and Brightness sliders. However, there are still times you may choose to use Levels within Photoshop, particularly if you want to make changes to only one area of your image. We’ll talk about making localized adjustments later in the chapter, but first we’ll cover how to use Levels to make a global adjustment. We recommend using Levels to adjust contrast and brightness rather than the adjustment called Brightness and Contrast because the Levels adjustment offers far more accurate control of your settings. In addition, you may opt to use Curves to increase the contrast in a particular range of tonalities rather than throughout the entire tonal range. We’ll talk about Curves later in this chapter. The primary component of the Levels dialog box is a histogram display (shown earlier in Figure 6.3) that charts the distribution of tonal values within your image. Those values are represented from black at the extreme left to white at the extreme right. This gradation of tonal values appears as a gradient bar along the bottom of the histogram chart. The shape of the histogram chart tells you about the distribution of tonal values within the image. For example, histogram data that is shifted toward the left indicates that the image is generally dark. However, that doesn’t necessarily tell you anything about the quality of the image; it may simply be a dark scene. Similarly, a brighter image has a histogram shifted toward the right. The key things to watch out for on the Levels histogram are clipping and gap- ping. Clipping is an indication that information has been lost in the highlights or shad- ows of your image. Gapping is represented by gaps in the histogram and indicates tonal values that are not represented in your image. Clipping is indicated on the histogram display by data running off the end of the chart. Clipping may be displayed in two ways. One is as a thin spike at one end of the chart. This is most commonly seen at the highlight end and is often caused by specular highlights within your image, such as reections from water, glass, or metal. In other words, it isn’t necessarily a major problem within the image because you don’t expect to see detail in such highlights. Note: As we mentioned in Chapter 1, clipping seen in a luminosity histogram always indicates that some pixels in your image are pure black or pure white, but clipping in an RGB histogram can occur when one or more channels has a value of 0 or 255. In such cases, there may or may not be black or white pixels in your image. For example, pure red would have RGB values of 255, 0, 0 and would indicate potential clipping at both ends of the histogram, even though the pixels are pure red, not black or white. The histogram in Levels shows RGB information or individual histograms for each of the channels. 607343c06.indd 235 4/12/10 11:42:40 PM . n 607343c06.indd 232 4/12/10 11:42:39 PM 233 ■ USING THE CS5 ADJUSTMENTS PANEL As we discussed in Chapter 3, “Adobe Camera Raw,” in Photoshop CS5 you can make most, if not all, your adjustments. for JPEGs and TIFFs. However, there are times you’ll choose to use the original tools within Photoshop. Although the exposure tools in ACR and Photoshop are very simi- lar, sometimes they differ. Exposure, Blacks, and Brightness sliders. However, there are still times you may choose to use Levels within Photoshop, particularly if you want to make changes to only one area of your image. We’ll