Tài liệu Photoshop cs5 by Dayley part 56 pptx

381 CHAPTER Lighting and Color Adjustments IN THIS CHAPTER Adjusting lighting and exposure Changing color balance Applying lens filter effects to photos Making specific color and tone adjustments to images Creating custom black and white photos Making colors pop out of images Adjusting levels in images to restore detail T he most common edit that you will perform on photos is correcting the lighting and color. Photoshop provides a number tools that cor- rect the color and lighting in different ways. As you become more familiar with these tools, you can adjust problems in images such as overex- posure, underexposure, and color casts. You also can make minute adjust- ments to images that make a big difference in the overall appearance. This chapter discusses most of the tools available in the Image ➪ Adjustments menu and the Adjustments panel. Many of these tools have overlapping functionality, so you are not locked into one specific tool to adjust an image. Try all the tools we discuss in this chapter, and then use the tools that work best for you. Note Remember that most of the techniques you learn in this chapter can be applied as an Adjustment layer. That means you can use a selection to create the Adjustment layer and then apply the color adjustments only to that specific area of the image. This allows you to be much more aggressive with the changes you make because you aren’t modifying the rest of the image. n Applying Quick Adjustments to Light and Color Photoshop provides several tools that allow you to make quick adjustments to the lighting and color in images. In the background, these tools are simply adjusting the level values in the color channels of the image. However, these tools provide a nice interface to adjust them in specific ways. I like to think of the adjustment tools as “canned” solutions to simple color and lighting issues. 20_584743-ch13.indd 38120_584743-ch13.indd 381 5/3/10 10:34 AM5/3/10 10:34 AM Part IV: Enhancing, Correcting, and Retouching 382 The following sections discuss using Photoshop’s adjustment tools to fix lighting and color prob- lems and make subtle adjustments that enhance the appearance of photos. These tools work well for most of the problems you encounter in images. Later in this chapter, we discuss using the Levels and Curves tools to make more complex adjustments that the simple tools can’t do. Brightness and contrast versus exposure One of the most common problems you may encounter with photos is that they are either too dark or to light due to lighting or exposure problems. Photoshop provides two tools to quickly fix light- ing problems in your images: the Brightness/ Contrast tool and the Exposure tool. To understand how these tools work, first look at the reason a photo is too dark or too light. Photos are too dark because not enough light was received by the camera, either because the aper- ture was too small or the exposure time was too short. The end result is that too many pixels are in the low levels of all color channels, making the image dark with limited details. The opposite is true for photos that are too light. Both the Brightness/ Contrast tool and the Exposure tool can be used to correct photos that have been overexposed or underexposed. However, they work a bit differently and produce different results. The biggest difference between the two tools is that the Contrast and Brightness tool works with the color space that exists in the image and the Exposure tool works with a linear color space called gamma 1.0. Because the Exposure tool is not limited to the current color space, it can make more dramatic lighting corrections. The downside of the Exposure tool is that when working out- side the color space in the image, some data loss occurs in the form of more abrupt changes between tones. Tip The Exposure tool was designed to be used in HDR images with much greater tonal ranges, even though it does work with 8-bit and 16-bit images. A good rule to follow is to use the Contrast and Brightness tool when working with 8-bit images and the Exposure tool when working with HDR images. Then, if you can’t get the lighting cor- rection you need with the Contrast and Brightness tool, you can use the Exposure tool to get a better result. n Using the Brightness/ Contrast tool to adjust lighting The Brightness/ Contrast tool, shown in the Adjustments panel of Figure 13.1, allows you to adjust both the brightness and contrast levels in an image. Here’s how: l Brightness: Adjusting the brightness up increases the level values of all color channels in an image, making the image lighter. Adjusting the brightness down decreases the level val- ues of all color channels in an image, making the image darker. l Contrast: Adjusting the contrast up spreads the level values out, generating more contrast between the levels in the image giving. Adjusting the contrast down contracts the level values more tightly, giving less contrast. 20_584743-ch13.indd 38220_584743-ch13.indd 382 5/3/10 10:34 AM5/3/10 10:34 AM Chapter 13: Lighting and Color Adjustments 383 Typically, to correct an image that is underexposed, you need to increase the brightness first and then increase the contrast to bring back some of the detail lost by increasing the brightness. To correct an image that is overexposed, you need to decrease the brightness and then increase the contrast to bring back the detail. Figure 13.1 shows the effects of adjusting the brightness and contrast on a photo that was underex- posed. Notice that by increasing the brightness and contrast, we can see more details in the photo. FIGURE 13.1 Increasing the brightness and contrast on an underexposed image reveals more of the detail. On the Web Site The image shown in Figure 13.1 can be found on this book’s Web site as Figure 13-1.psd. You can open it in Photoshop and try adjusting the brightness and contrast. n Using the Exposure tool to adjust lighting The Exposure tool, shown in the Adjustments panel of Figure 13.2, allows you to adjust the expo- sure values of the image, increasing or decreasing the lighting and contrast. The Exposure tool allows you to set the following values to adjust the lighting and contrast: l Exposure: This adjusts the highlight end of the tonal scale. Adjusting the exposure up lightens the lighter pixels. Adjusting the exposure down darkens the lighter pixels. This setting has only a minimal effect in the darkest pixels of the image. l Offset: This adjusts the darker and middle end of the tonal scale. Adjusting the offset up lightens the darker pixels. Adjusting the offset down darkens the midtone and darker pix- els. This setting has only a minimal effect in the lightest pixels of the image. l Gamma Correction: This applies gamma correction to the image. Adjusting the gamma value down (between 1 and 0) darkens the image and adjusting the gamma up (between 1 and 10) lightens the image. 20_584743-ch13.indd 38320_584743-ch13.indd 383 5/3/10 10:34 AM5/3/10 10:34 AM Part IV: Enhancing, Correcting, and Retouching 384 l Black eyedropper: When you use the black eyedropper to select a pixel in the image, the Offset value is adjusted by setting the selected pixel to zero. l White eyedropper: When you use the white eyedropper to select a pixel in the image, the Exposure value is adjusted by setting the selected pixel to white. White is 1.0 for HDR images and 0.0 for non-HDR images. l Midtone eyedropper: When you use the midtone eyedropper to select a pixel in the image, the Exposure value is adjusted by setting the selected pixel to midtone gray. Note You also can select a preset exposure value of minus 1.0, minus 2.0, plus 1.0, plus 2.0, or a custom value from the Exposure drop-down menu shown in Figure 13.3. This allows you to create a custom exposure setting that can be saved using the Save Exposure Preset option in the Adjustments panel menu. The custom exposure can then be applied to several different images that had the same exposure problems. n Follow these steps to use the Exposure tool to adjust the lighting and contrast of an image in Photoshop: 1. Select Window ➪ Adjustments from the main menu to load the Adjustments panel (refer to Figure 13.2). 2. Click the Exposure button (refer to Figure 13.2) to add an Exposure adjustment layer to the image. The Exposure dialog box, shown in Figure 13.3, appears, allowing you to adjust the exposure settings. FIGURE 13.2 Selecting the Exposure button from the Adjustment panel home pane 20_584743-ch13.indd 38420_584743-ch13.indd 384 5/3/10 10:34 AM5/3/10 10:34 AM Chapter 13: Lighting and Color Adjustments 385 3. Try to use the eyedroppers to set a baseline for setting the exposure. Use the black eyedropper to select an item in the image that should be black, the white eye- dropper to select a white pixel, and the midtone eyedropper to select a gray pixel. On many photos, the eyedroppers simply don’t work; if they don’t work, just move to the next step. 4. Adjust the Exposure to get the overall light pixels in the image to show as much detail as possible. Don’t worry if the image looks a bit faded out at this point. 5. Adjust the Offset, typically in the opposite direction than you adjusted the Exposure, until the image is less faded. 6. Adjust the Gamma Correction until the image looks better. 7. Tweak the Exposure, Offset, and Gamma Correction settings until you get the best overall lighting and contrast in the image. Figure 13.3 shows the effects of adjusting the Exposure, Offset, and Gamma Correction settings on a photo that was severely underexposed. Notice that increasing the Exposure allows you to see much more details in the image. However, the image is now a bit grainy because we adjusted the values outside the tonal range of the image. FIGURE 13.3 Increasing the Exposure and decreasing the Offset on an underexposed image in the Exposure tool reveals much more of the detail in the image. Black eyedropper Mid-tone eyedropper White eyedropper Exposure drop-down menu 20_584743-ch13.indd 38520_584743-ch13.indd 385 5/3/10 10:34 AM5/3/10 10:34 AM Part IV: Enhancing, Correcting, and Retouching 386 On the Web Site The image shown in Figure 13.3 can be found on this book’s Web site as Figure 13-3.psd. You can open it in Photoshop and try adjusting the exposure. n Changing the color balance The Color Balance Adjustment tool allows you to adjust the balance between each color in the color channels with its complementary color. Changing the color balance adjusts the overall hue of the color channel. This allows you to quickly fix a single color that is out of place or adjust all the colors in the image. Tip The Color Balance tool is extremely useful when you are trying to add color to a black and white image. You can select specific areas of the image and adjust the color balance to those areas to create color tones. n l Tone: A really nice feature of the Color Balance Adjustment tool, shown in the Adjustments panel of Figure 13.5, is the ability to specify whether you want to adjust the color balance for the pixels in the highlights, midtones, or shadows range. Separating the color balance into tonal ranges allows you to focus in on one specific tonal range, fixing the color for that range before moving on. l Color Sliders: To adjust the color balance, simply drag the color sliders to the left or right to adjust the balance between each color and its complementary color. Adjusting the bal- ance shifts the hue of the color, for example, from red to cyan or blue to yellow. l Preserve Luminosity: You can specify whether to preserve the luminosity, which typi- cally is the best idea. Preserving the luminosity forces the color balance adjustments to change so that the luminosity stays the same. This keeps the color balance adjustments from washing out the image. The following example demonstrates how to use the Color Balance Adjustment tool to fix the col- ors in an image that has been overloaded with a single tone: 1. Open the image in Photoshop, as shown in Figure 13.4. The orange leaves of the background have really added a yellow hue to the entire image, and none of the colors really pop out. 2. Select Window ➪ Adjustments from the main menu to load the Adjustments panel shown in Figure 13.5. 3. Click the Color Balance button shown in Figure 13.5 to add a Color Balance Adjustment layer to the image. The Color Balance pane appears, allowing you to adjust the color balance settings. 20_584743-ch13.indd 38620_584743-ch13.indd 386 5/3/10 10:34 AM5/3/10 10:34 AM . 38120_584743-ch13.indd 381 5/3/10 10:34 AM5/3/10 10:34 AM Part IV: Enhancing, Correcting, and Retouching 382 The following sections discuss using Photoshop s adjustment tools to fix lighting and color. AM5/3/10 10:34 AM Part IV: Enhancing, Correcting, and Retouching 384 l Black eyedropper: When you use the black eyedropper to select a pixel in the image, the Offset value is adjusted by setting the. 10:34 AM Part IV: Enhancing, Correcting, and Retouching 386 On the Web Site The image shown in Figure 13.3 can be found on this book’s Web site as Figure 13-3.psd. You can open it in Photoshop