Photoshop 6 for Windows Bible- P28 pptx

783 Chapter 17 ✦ Mapping and Adjusting Colors Consider the digital photograph featured in Color Plate 17-12. Snapped several years back in Boston’s Copley Square using a Kodak DC50 digital camera, the original image at the top of the color plate is drab and lifeless. If I used the Hue/Saturation command to pump up the saturation levels, a world of ugly detail rises out of the muck, as shown in the second example. (Obviously, I’ve taken the saturation a little too high, but only to demonstrate a point.) The detail would have faired no better if I had used the Variations command to boost the saturation. Unstable colors may be the result of JPEG compression, as in the case of the digital photo. Or you may have bad scanning or poor lighting to thank. In any case, you can correct the problem using our friends the Median and Gaussian Blur commands, as I explain in the following steps. If you find yourself working with heavily compressed images on a regular basis, you may want to record these steps with the Actions palette, as explained in Chapter B on the CD-ROM at the back of this book. Unlike the “Adjusting the Focus of Digital Photos” steps back in Chapter 10, you won’t want to apply these steps to every dig- ital photograph you take — or even most of them — but they come in handy more often than you might think. STEPS: Boosting the Saturation of Digital Photos 1. Select the entire image and copy it to a new layer. It seems like half of all Photoshop techniques begin with Ctrl+A and Ctrl+J. 2. Press Ctrl+U to display the Hue/Saturation dialog box. Then raise the Saturation value to whatever setting you desire. Don’t worry if your image starts to fall apart — that’s the whole point of these steps. Pay attention to the color and don’t worry about the rest. In the second example in Color Plate 17-12, I raised the Saturation to +80. 3. Choose Filter ➪ Noise ➪ Median. As you may recall from the last module, Median is the preeminent JPEG image fixer. A Radius value of 4 or 5 pixels works well for most images. You can take it even higher when working with resolutions of 200 ppi or more. I used 5. This destroys the detail, but that’s not important. The color is all that matters. 4. Choose Filter ➪ Blur ➪ Gaussian Blur. As always, the Median filter introduces its own edges. And this is one case where you don’t want to add any edges, so blur the heck out of the layer. I used a Radius of 4.0, just 1 pixel less than my Median Radius value. 5. Select Color from the blend mode pop-up menu in the Layers palette. Photoshop mixes the gummy, blurry color with the crisp detail underneath. I also lowered the Opacity to 70 percent to produce the third example in Color Plate 17-12. 784 Part V ✦ Color for Print and the Web My image was still a little soft, so I applied the digital-photo sharpening steps from Chapter 10. After flattening the image, I pressed Ctrl+A and Ctrl+J again to copy it to yet another new layer. Then I applied the Median, Gaussian Blur, and Unsharp Mask filters, flattened the image one last time, and sharpened the image to taste. The finished result appears at the bottom of Color Plate 17-12. Although a tad too colorful — Boston’s a lovely city, but it’s not quite this resplendent — the edges look every bit as good as they did in the original photograph, and in many ways better. Making Custom Brightness Adjustments The Lighter and Darker options in the Variations dialog box are preferable to the Lightness slider bar in the Hue/Saturation dialog box because you can specify whether to edit the darkest, lightest, or medium colors in an image. But neither command is adequate for making precise adjustments to the brightness and con- trast of an image. Photoshop provides two expert-level commands for adjusting the brightness levels in both grayscale and color images: ✦ The Levels command is great for most color corrections. It lets you adjust the darkest values, lightest values, and midrange colors with a minimum of fuss and a generous amount of control. ✦ The Curves command is great for creating special effects and correcting images beyond the help of the Levels command. Using the Curves command, you can map every brightness value in every color channel to an entirely dif- ferent brightness value. In the back rooms of some print houses and art shops, a controversy is brewing over which command is better, Levels or Curves. Based on a few letters I’ve received over the years, it seems that some folks consider Curves to be the command for real men and Levels suitable only for color-correcting wimps. Naturally, this is a big wad of hooey. Levels provides a histogram, which is abso- lutely essential for gauging the proper setting for black and white points. Meanwhile, Curves lets you map out a virtually infinite number of significant points on a graph. The point is, both commands have their advantages, and both offer practical bene- fits for intermediate and advanced users alike. There’s no substitute for a good histogram, so I prefer to use Levels for my day-to- day color correcting. If you can’t quite get the effect you want with Levels, or you know that you need to map specific brightness values in an image to other values, use Curves. The Curves command is the more powerful function, but it is likewise more cumbersome. Note 785 Chapter 17 ✦ Mapping and Adjusting Colors The Levels command When you choose Image ➪ Adjust ➪ Levels (Ctrl+L), Photoshop displays the Levels dialog box shown in Figure 17-15. The dialog box offers a histogram, as explained in the “Threshold” section earlier in this chapter, as well as two sets of slider bars with corresponding option boxes and a few automated eyedropper options in the lower-right corner. You can compress and expand the range of brightness values in an image by manipulating the Input Levels options. Then you can map those bright- ness values to new brightness values by adjusting the Output Levels options. Figure 17-15: Use the Levels dialog box to map brightness values in the image (Input Levels) to new brightness values (Output Levels). The options in the Levels dialog box work as follows: ✦ Channel: Select the color channel that you want to edit from this pop-up menu. You can apply different Input Levels and Output Levels values to each color channel. However, the options along the right side of the dialog box affect all colors in the selected portion of an image regardless of which Channel option is active. ✦ Input Levels: Use these options to modify the contrast of the image by dark- ening the darkest colors and lightening the lightest ones. The Input Levels option boxes correspond to the slider bar immediately below the histogram. You map pixels to black (or the darkest Output Levels value) by entering a number from 0 to 255 in the first option box or by dragging the black slider triangle. For example, if you raise the value to 55, all colors with brightness values of 55 or less in the original image become black, darkening the image as shown in the first example of Figure 17-16. 786 Part V ✦ Color for Print and the Web You can map pixels at the opposite end of the brightness scale to white (or the lightest Output Levels value) by entering a number from 0 to 255 in the last option box or by dragging the white slider triangle. If you lower the value to 200, all colors with brightness values of 200 or greater become white, light- ening the image as shown in the second example of Figure 17-16. In the last example of the figure, I raised the first value and lowered the last value, thereby increasing the amount of contrast in the image. One of my favorite ways to edit the Input Levels values is to press the up and down arrow keys. Each press of an arrow key raises or lowers the value by 1. Press Shift with an arrow key to change the value in increments of 10. Figure 17-16: The results of raising the first Input Levels value to 55 (left), lowering the last value to 200 (middle), and combining the two (right). ✦ Gamma: The middle Input Levels option box and the corresponding gray triangle in the slider bar (shown highlighted in Figure 17-17) represent the gamma value, which is the brightness level of the medium gray value in the image. The gamma value can range from 0.10 to 9.99, with 1.00 being dead-on medium gray. Any change to the gamma value has the effect of decreasing the amount of contrast in the image by lightening or darkening grays without changing shadows and highlights. Increase the gamma value or drag the gray slider triangle to the left to lighten the medium grays (also called midtones), as in the first and second examples of Figure 17-18. Lower the gamma value or drag the gray triangle to the right to darken the medium grays, as in the last example in the figure. Tip 787 Chapter 17 ✦ Mapping and Adjusting Colors You can edit the gamma value also by pressing the up and down arrow keys. Pressing an arrow key changes the value by 0.01; pressing Shift+arrow changes the value by 0.10. I can’t stress enough how useful this technique is. I rarely do anything except press arrow keys inside the Levels dialog box anymore. Figure 17-17: To create the spotlighting effects you see here, I selected the circular areas, inversed the selection, and applied the values shown in this very dialog box. Figure 17-18: The results of raising (left and middle) and lowering (right) the gamma value to lighten and darken the midtones in an image. 788 Part V ✦ Color for Print and the Web ✦ Output Levels: Use these options to curtail the range of brightness levels in an image by lightening the darkest pixels and darkening the lightest pixels. You adjust the brightness of the darkest pixels — those that correspond to the black Input Levels slider triangle — by entering a number from 0 to 255 in the first option box or by dragging the black slider triangle. For example, if you raise the value to 55, no color can be darker than that brightness level (roughly 80 percent black), which lightens the image as shown in the first example of Figure 17-19. You adjust the brightness of the lightest pixels— those that correspond to the white Input Levels slider triangle—by entering a number from 0 to 255 in the second option box or by dragging the white slider triangle. If you lower the value to 200, no color can be lighter than that brightness level (roughly 20 percent black), darkening the image as shown in the second example of Figure 17-19. In the last example of the figure, I raised the first value and lowered the second value, thereby dramatically decreasing the amount of contrast in the image. You can fully or partially invert an image using the Output Levels slider trian- gles. Just drag the black triangle to the right and drag the white triangle to the left past the black triangle. The colors flip, whites mapping to dark colors and blacks mapping to light colors. Figure 17-19: The result of raising the first Output Levels value to 55 (left), lowering the second value to 200 (middle), and combining the two (right). 789 Chapter 17 ✦ Mapping and Adjusting Colors ✦ Load/Save: You can load and save settings to disk using these buttons. ✦ Auto: Click the Auto button to automatically map the darkest pixel in your selection to black and the lightest pixel to white, as if you had chosen Image ➪ Adjust ➪ Auto Levels. Photoshop actually darkens and lightens the image by an extra half a percent just in case the darkest and lightest pixels are statisti- cally inconsistent with the rest of the image. To enter a percentage of your own, Alt-click the Auto button (the button name changes to Options). This displays two additional options, Black Clip and White Clip. Enter higher values to increase the number of pixels mapped to black and white; decrease the values to lessen the effect. Figure 17-20 compares the effect of the default 0.50 percent values to higher values of 2.50 and 9.99 percent. As you can see, raising the Clip value produces higher contrast effects. Figure 17-20: The default effect of the Auto button (left) and the effect of the Auto button after raising the Clip values (middle and right). Any changes made in the Auto Range Options dialog box also affect the per- formance of the Auto Levels command. At all times, the effects of the Auto button and Auto Levels command are identical. ✦ Eyedroppers: Select one of the eyedropper tools in the Levels dialog box and click a pixel in the image window to automatically adjust the color of that pixel. If you click a pixel with the black eyedropper tool (the first of the three), Photoshop maps the color of the pixel and all darker colors to black. If you click a pixel with the white eyedropper tool (the last of the three), Note 0.50% Clips 2.50% Clips 9.99% Clips 790 Part V ✦ Color for Print and the Web Photoshop maps it and all lighter colors to white. Use the gray eyedropper tool (middle) to change the color you clicked to medium gray and adjust all other colors in accordance. For example, if you click a light pixel, all light pix- els change to medium gray and all other pixels change to even darker colors. One way to use the eyedropper tools is to color-correct scans without a lot of messing around. Include a neutral swatch of gray with the photograph you want to scan. (For those who own a Pantone swatch book, Cool Gray 5 or 6 is your best bet.) After opening the scan in Photoshop, choose the Levels com- mand, select the gray eyedropper tool, and click the neutral gray swatch in the image window. This technique won’t perform miracles, but it will help you to distribute lights and darks in the image more evenly. You then can fine-tune the image using the Input Levels and Output Levels options. By default, the eyedroppers map to white, gray, and black. But you can change that. Double-click any one of the three eyedroppers to display the Color Picker dialog box. For example, suppose you double-click the white eyedropper, set the color values to C:2, M:3, Y:5, K:0, and then click a pixel in the image win- dow. Instead of making the pixel white, Photoshop changes the clicked color — and all colors lighter than it — to C:2, M:3, Y:5, K:0, which is great for avoiding hot highlights and ragged edges. To give you a sense of how the Levels command works, the following steps describe how to improve the appearance of an overly dark, low-contrast image such as the first example in Color Plate 17-13. Thanks to natural lighting and the dark color of the stone, this statue of Thomas Jefferson is hardly recognizable. Luckily, you can bring out the highlights using Levels. STEPS: Correcting Brightness and Contrast with the Levels Command 1. Press Ctrl+L to display the Levels dialog box. The histogram for the Jefferson image appears superimposed in white in front of the great man’s chest. As you can see, most of the colors are clustered on the left side of the graph, showing that there are far more dark colors than light. 2. Press Ctrl+1 to examine the red channel. Assuming that you’re editing an RGB image, Ctrl+1 displays a histogram for the red channel. The channel-specific his- tograms appear below Jefferson, colorized for your viewing pleasure. 3. Edit the black Input Levels value as needed. Drag the black slider triangle to below the point at which the histogram begins. In the case of Jefferson, you can see a spike in the histogram about a half pica in from the left side of the graph. I dragged the black triangle directly underneath that spike, changing the first Input Levels value to 14, as you can see in the red histogram on the right side of Color Plate 17-13. Tip Tip 791 Chapter 17 ✦ Mapping and Adjusting Colors 4. Edit the white Input Levels value. Drag the white slider triangle to below the point at which the histogram ends. In the color plate, the histogram features a tall spike on the far right side. This means a whole lot of pixels are already white. I don’t want to create a flat hot spot, so I leave the white triangle alone. 5. Edit the gamma value. Drag the gray triangle to the gravitational center of the histogram. Imagine that the histogram is a big mass, and you’re trying to bal- ance the mass evenly on top of the gray triangle. Because my histogram is weighted too heavily to the left, I had to drag the gray triangle far to the left until the middle Input Levels value changed to 2.40, which represents a radi- cal shift. 6. Repeat Steps 2 through 5 for the green and blue channels. Ctrl+2 takes you to the green channel; Ctrl+3 takes you to blue. Your image probably has a sig- nificant preponderance of red about it. To correct this, you need to edit the green and blue channels in kind. The graphs on the right side of Color Plate 17-13 show how I edited my histograms. Feel free to switch back and forth between channels as much as you like to get everything just right. 7. Press Ctrl+tilde (~) to return to the composite RGB histogram. After you get the color balance right, you can switch back to the composite mode and fur- ther edit the Input Levels. I typically bump up the gamma a few notches — to 1.2 or so — to account for dot gain. You may notice that your RGB histogram has changed. Although the histograms in the individual color channels remain fixed, the composite histogram updates to reflect the red, green, and blue modifications. I’ve superimposed the updated histogram in white on the corrected Jefferson on the right side of Color Plate 17-13. As you can see, the colors are now better distributed across the bright- ness range. 8. Press Enter to apply your changes. Just for fun, press Ctrl+Z a few times to see the before and after shots. Quite the transformation, eh? If you decide after looking at the before and after views that you could do a better job, undo the color correction and press Ctrl+Alt+L to bring up the Levels dialog box with the previous settings intact. Now you can take up where you left off. The Curves command If you want to be able to map any brightness value in an image to absolutely any other brightness value — no holds barred, as they say—you want the Curves com- mand. When you choose Image ➪ Adjust ➪ Curves (Ctrl+M), Photoshop displays the Curves dialog box, shown in Figure 17-21, which offers access to the most complex and powerful color correction options on the planet. Tip 792 Part V ✦ Color for Print and the Web Figure 17-21: The Curves dialog box lets you distribute brightness values by drawing curves on a graph. Quickly, here’s how the options work: ✦ Channel: Surely you know how this option works by now. You select the color channel that you want to edit from this pop-up menu. You can apply different mapping functions to different channels by drawing in the graph below the pop-up menu. But, as is always the case, the options along the right side of the dialog box affect all colors in the selected portion of an image regardless of which Channel option is active. ✦ Brightness graph: The brightness graph is where you map brightness values in the original image to new brightness values. The horizontal axis of the graph represents input levels; the vertical axis represents output levels. The bright- ness curve charts the relationship between input and output levels. The lower- left corner is the origin of the graph (the point at which both input and output values are 0). Move right in the graph for higher input values and up for higher output values. Because the brightness graph is the core of this dialog box, upcoming sections explain it in more detail. By default, a trio of horizontal and vertical dotted lines crisscross the bright- ness graph, subdividing it into quarters. For added precision, you can divide the graph into horizontal and vertical tenths. Just Alt-click inside the graph to toggle between tenths and quarters. Tip Brightness curveBrightness graph Brightness bar Curve tools Eyedroppers [...]... equally ready to help Photoshoppers on both PC and Mac platforms, but many will take your Photoshop file and run it through a Mac Nothing is wrong with this — Photoshop is nearly identical on the two platforms — but cross-platform problems may crop up Whenever possible, be sure your service bureau knows how to address cross-platform incompatibilities and has a general working knowledge of Windows ✦ Commercial... to paint the correction back in Note In fact, if a selection is active when you create a new adjustment layer, Photoshop automatically creates a layer mask according to the selection outline For example, in Color Plate 17- 16, I selected the topiary dinosaur before creating the Levels layer Photoshop thoughtfully converted my selection into a layer mask, as labeled in Figure 17-31 And like any layer... without the pain Photoshop Chapter 17 ✦ Mapping and Adjusting Colors 6 ✦ Change one adjustment to another: After applying one kind of adjustment layer, you can convert it to another kind of adjustment layer For example, you could swap an existing Levels adjustment for a Curves adjustment To do so, choose the desired color adjustment from the Layer ➪ Change Layer Content submenu Photoshop doesn’t try... (dynamic link library, a basic component of Windows) with a later printer driver If you encounter a Windows- related printing problem, your first cry for help should be to your printer manufacturer’s Web site or tech support line If those sources don’t have the answer, check online forums and newsgroups Your service bureau can also be an excellent source for technical advice Chances are, you’re not... the new point 795 7 96 Part V ✦ Color for Print and the Web Photoshop Figure 17-24: Use the standard eyedropper cursor to locate a color in the brightness graph (left) Click with one of the eyedropper tools from the Curves dialog box to map the color of that pixel in the graph (middle) You then can edit the location of the point in the graph by dragging it (right) Gradient maps 6 Photoshop has long permitted... each printout to a plate, which is used in the actual reproduction process ✦ Duotone: A grayscale image in Photoshop can contain as many as 2 56 brightness values, from white on up to black A printer can convey significantly fewer shades A laser printer, for example, provides anywhere from 26 to 65 shades An imagesetter provides from 150 to 200 shades, depending on resolution and screen frequency And... options available for printing composite images Later in this chapter, I cover color separations and duotones Like any Windows application, Photoshop can print composite images to nearly any output device you can hook up to your computer Assuming your printer is turned 811 812 Part V ✦ Color for Print and the Web on, properly attached, and in working order, printing a composite image from Photoshop is a... V ✦ Color for Print and the Web The pencil tool lets you draw free-form curves simply by dragging inside the graph, as illustrated in Figure 17-23 This pencil works much like Photoshop s standard pencil tool This means you can draw straight lines by clicking one location in the graph and Shift-clicking a different point Pencil tool Point tool Figure 17-23: Use the pencil tool to draw free-form lines... Rather than communicating directly with the output device, Photoshop describes the image to the system software Under Windows 98, Me, NT, and 2000, set spooling options via the Printer control panel Choose Settings ➪ Printers, right-click the icon for your specific printer, and choose Properties from the pop-up menu 809 810 Part V ✦ Color for Print and the Web Inside the printer’s Properties dialog... composite curve If the Red channel is visible, Photoshop adds the point to the red graph and leaves the green and blue graphs unchanged ✦ To add a color to all graphs, regardless of which channel is visible in the Curves dialog box, Ctrl+Shift-click a pixel in the image window In the case of an RGB image, Photoshop maps the red, green, and blue brightness values for that pixel to each of the red, green, . to apply your changes. Just for fun, press Ctrl+Z a few times to see the before and after shots. Quite the transformation, eh? If you decide after looking at the before and after views that you. the command for real men and Levels suitable only for color-correcting wimps. Naturally, this is a big wad of hooey. Levels provides a histogram, which is abso- lutely essential for gauging the. advantages, and both offer practical bene- fits for intermediate and advanced users alike. There’s no substitute for a good histogram, so I prefer to use Levels for my day-to- day color correcting. If