Photoshop 6 for Windows Bible- P28

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Photoshop 6 for Windows Bible- P28:If you are reading this foreword, it probably means that you’ve purchased a copy of Adobe Photoshop 6.0, and for that I and the rest of the Photoshop team at Adobe thank you. If you own a previous edition of the Photoshop Bible, you probably know what to expect. If not, then get ready for an interesting trip.

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Chapter 17 ✦ Mapping and Adjusting Colors 783 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. Note 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.
Chapter 17 ✦ Mapping and Adjusting Colors 785 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. Tip 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.
Chapter 17 ✦ Mapping and Adjusting Colors 787 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).
Chapter 17 ✦ Mapping and Adjusting Colors 789 ✦ 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. 0.50% Clips 2.50% Clips 9.99% Clips 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). Note 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),
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. Tip 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. Tip 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.
Chapter 17 ✦ Mapping and Adjusting Colors 791 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? Tip 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.
792 Part V ✦ Color for Print and the Web Brightness graph Brightness curve Eyedroppers Brightness bar Curve tools 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. Tip 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.
Chapter 17 ✦ Mapping and Adjusting Colors 793 ✦ Brightness bar: The horizontal brightness bar shows the direction of light and dark values in the graph. When the dark end of the brightness bar appears on the left — as by default when editing an RGB image — colors are measured in terms of brightness values. The colors in the graph proceed from black on the left to white on the right, as demonstrated in the left example of Figure 17-22. Therefore, higher values produce lighter colors. This is my preferred setting because it measures colors in the same direction as the Levels dialog box. If you click the brightness bar, white and black switch places, as shown in the second example of the figure. The result is that Photoshop measures the col- ors in terms of ink coverage, from 0 to 100 percent of the primary color. Higher values now produce darker colors. This is the default setting for grayscale and CMYK images. Brightness values Ink coverage Figure 17-22: Click the brightness bar to change the way in which the graph measures color: by brightness values (left) or by ink coverage (right). ✦ Curve tools: Use the curve tools to draw the curve inside the brightness graph. The point tool (labeled in Figure 17-23) is selected by default. Click in the graph with this tool to add a point to the curve. Drag a point to move it. To delete a point, Ctrl-click it.
794 Part 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 in the brightness graph. If the lines appear rough, you can soften them by clicking on the Smooth button. ✦ Input and Output values: The Input and Output values monitor the location of your cursor in the graph according to brightness values or ink coverage, depending on the setting of the brightness bar. You can modify the Input and Output values when working with the point tool. Just click the point on the graph that you want to adjust and then enter new values. The Input number rep- resents the brightness or ink value of the point before you entered the Curves dialog box; the Output number represents the new brightness or ink value. Tip You can change the Output value also by using the up and down arrow keys. Click the point you want to modify. Then press the up or down arrow key to raise or lower the Output value by 1. Press Shift+up or down arrow to change the Output value in increments of 10. Note that these techniques — and ones that follow — work only when the point tool is active. (You can’t change points with the pencil tool.) When editing multiple graph points from the keyboard, it’s helpful to be able to activate the points from the keyboard as well. To advance from one point
Chapter 17 ✦ Mapping and Adjusting Colors 795 to the next, press Ctrl+Tab. To select the previous point, press Ctrl+Shift+Tab. To deselect all points, press Ctrl+D. ✦ Load/Save: Use these buttons to load and save settings to disk. ✦ Smooth: Click the Smooth button to smooth out curves drawn with the pencil tool. Doing so leads to smoother color transitions in the image window. This button is dimmed except when you use the pencil tool. ✦ Auto: Click this button to automatically map the darkest pixel in your selec- tion to black and the lightest pixel to white. Photoshop throws in some addi- tional darkening and lightening according to the Clip percentages, which you can edit by Alt-clicking on the button. ✦ Eyedroppers: If you move the cursor out of the dialog box and into the image window, you get the standard eyedropper cursor. Click a pixel in the image to locate the brightness value of that pixel in the graph. A circle appears in the graph, and the Input and Output numbers list the value for as long as you hold down the mouse button, as shown in the first example in Figure 17-24. The other eyedroppers work as they do in the Levels dialog box, mapping pix- els to black, medium gray, or white (or other colors if you double-click the eye- dropper icons). For example, the second image in Figure 17-24 shows the white eyedropper tool clicking on a light pixel, thereby mapping that value to white, as shown in the highlighted portion of the graph below the image. Note Bear in mind that Photoshop maps the value to each color channel indepen- dently. So when editing a full-color image inside the Curves dialog box, you have to switch channels to see the results of clicking with the eyedropper. You can further adjust the brightness value of that pixel by dragging the corre- sponding point in the graph, as demonstrated in the last example of the figure. Tip The eyedropper tools aren’t the only way to add points to a curve from the image window. Photoshop offers two more keyboard tricks that greatly sim- plify the process of pinpointing and adjusting colors inside the Curves dialog box. Bear in mind, both of these techniques work only when the point tool is active: ✦ To add a color as a point along the Curves graph, Ctrl-click a pixel in the image window. Photoshop adds the point to the channel displayed in the dialog box. For example, if the RGB composite channel is visible, the point is added to the RGB 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, and blue graphs in the Curves dialog box. The RGB composite graph shows no change — switch to the individual chan- nels to see the new point.
796 Part V ✦ Color for Print and the Web 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 Photoshop 6 Photoshop has long permitted you to apply a gradation as a Curves map, but Version 6 makes it easier than ever before. Just choose Image ➪ Adjust ➪ Gradient Map to display the dialog box pictured in Figure 17-25. Make sure the Preview check box is turned on. Then click the down-pointing arrowhead to the right of the gradi- ent preview to display the familiar gradient drop-down palette. Select a gradient other than Foreground To Background and watch the fireworks. In the psychedelic Color Plate 17-14, I cloned Constantine to a new layer and applied a heavy dose of Gaussian Blur. Then I used the Gradient Map command to apply each of three custom Curves maps. In the bottom row, I mixed these fantastic images with their underlying originals using the Color blend mode.
Chapter 17 ✦ Mapping and Adjusting Colors 797 Figure 17-25: Choose the Gradient Map command to apply a preset gradient as a Curves map. Color Plate 17-14 shows examples. What’s going on? As foreign as it may sound, any gradient can be expressed as a Curves graph, progressing through a variety of brightness values in each of the three (RGB) or four (CMYK) color channels. When applied as a gradient map, the begin- ning of the gradient maps black; the end of the gradient maps white. If you apply the Violet, Orange preset, for example, the dark colors in the image map to violet and the light colors map to orange. Noise-type gradients (introduced in the “Applying Gradient Fills” section of Chapter 6) produce especially interesting effects. Practical applications: continuous curves Note Due to the complex nature and general usefulness of the Curves dialog box, I spend this section and the next exploring practical applications of its many options, con- centrating first on the point tool and then on the pencil tool. These discussions assume that the brightness bar is set to edit brightness values, so that the gradation in the bar lightens from left to right. If you set the bar to edit ink coverage — where the bar darkens from left to right — you can still achieve the effects I describe, but you must drag in the opposite direction. For example, if I tell you to lighten colors by dragging upward, you would drag downward. When you first enter the Curves dialog box, the brightness curve appears as a straight line strung between two points, as shown in the first example of Figure 17-26, mapping every input level from black (the lower-left point) to white (the upper-right point) to an identical output level. If you want to perform seamless color corrections, the point tool is your best bet because it enables you to edit the levels in the bright- ness graph while maintaining a continuous curve.
798 Part V ✦ Color for Print and the Web Figure 17-26: Create a single point in the curve with the point tool (left) and then drag it upward (middle) or downward (right) to lighten or darken the image evenly. To lighten the colors, click near the middle of the curve with the point tool to cre- ate a new point and then drag the point upward, as demonstrated in the second example of Figure 17-26. To darken the image, drag the point downward, as in the third example. Create two points in the curve to boost or lessen the contrast between colors in the image. In the first example of Figure 17-27, I created one point very near the white point in the curve and another point very close to the black point. I then dragged down on the left point and up on the right point to make the dark pixels darker and the light pixels lighter, which translates to higher contrast. In the second example of the figure, I did just the opposite, dragging up on the left point to lighten the dark pixels and down on the right point to darken the light pix- els. As you can see in the second image, this lessens the contrast between colors, making the image more gray.
Chapter 17 ✦ Mapping and Adjusting Colors 799 In the previous example, in Figure 17-27, I bolstered the contrast with a vengeance by dragging the right point down and to the left. This has the effect of springing the right half of the curve farther upward, thus increasing the brightness of the light pixels in the image. Figure 17-27: Create two points in the curve to change the appearance of contrast in an image, whether by increasing it mildly (left), decreasing it (middle), or boosting it dramatically (right). Practical applications: arbitrary curves You can create some mind-numbing color variations by adjusting the brightness curve arbitrarily, mapping light pixels to dark, dark pixels to light, and in-between pixels all over the place. In the first example of Figure 17-28, I used the point tool to achieve an arbitrary curve. By dragging the left point severely upward and the right point severely downward, I caused dark and light pixels alike to soar across the spectrum.
800 Part V ✦ Color for Print and the Web If you’re interested in something a little more subtle, try applying an arbitrary curve to a single channel in a color image. Color Plate 17-15, for example, shows an image subject to relatively basic color manipulations in the red and green channels, followed by an arbitrary adjustment to the blue channel. Although you can certainly achieve arbitrary effects using the point tool, the pencil tool is more versatile and less inhibiting. As shown in the second example of Figure 17-28, I created an effect that would alarm Carlos Castaneda just by zigzagging my way across the graph and clicking on the Smooth button. Figure 17-28: These arbitrary brightness curves were created using the point tool (left) and the pencil tool (right). In fact, the Smooth button is an integral part of using the pencil tool. Try this little experiment: Draw a bunch of random lines and squiggles with the pencil tool in the brightness graph. As shown in the first example of Figure 17-29, your efforts will most likely yield an unspeakably hideous and utterly unrecognizable effect. Next, click the Smooth button. Photoshop automatically connects all portions of the curve, miraculously smoothing out the color-mapping effect and rescuing some semblance of your image, as shown in the second example of the figure. If the effect is still too radical, you can continue to smooth it by clicking the Smooth button additional times. I clicked on the button twice more to create the right image in Figure 17-29. Eventually, the Smooth button restores the curve to a straight line.
Chapter 17 ✦ Mapping and Adjusting Colors 801 Figure 17-29: After drawing a series of random lines with the pencil tool (left), I clicked on the Smooth button once to connect the lines into a frenetic curve (middle) and then twice more to even out the curve, thus preserving more of the original image (right). Adjustment Layers Every one of the commands I’ve discussed in this chapter is applicable to a single layer at a time. If you want to correct the colors in multiple layers, you have to cre- ate a special kind of layer called an adjustment layer. Adjustment layers are layers that contain mathematical color correction information. The layer applies its cor- rections to all layers beneath it, without affecting any layers above. You can create an adjustment layer in one of two ways: ✦ Choose Layer ➪ New Adjustment Layer. This displays a submenu of color adjustment commands, ranging from Levels and Curves to Invert, Threshold, and Posterize. ✦ Click the half black/half white circle at the bottom of the Layers palette, as shown in Figure 17-30. The first three options — Solid Color, Gradient, and Pattern Layer — are dynamic fill layers, as discussed in Chapter 14. Choose any one of the remaining 11 options to make a new adjustment layer.
802 Part V ✦ Color for Print and the Web Click here Figure 17-30: Click the black-and-white circle to display a pop-up menu of dynamic fill and adjustment layers. If you choose a command from the Layer ➪ New Adjustment Layer submenu, Photo- shop displays the New Layer dialog box, which permits you to name the layer, assign a color, and set the blend mode. If you choose an option from the black-and-white cir- cle in the Layers palette (labeled in Figure 17-30), Photoshop bypasses the New Layer dialog box and heads straight to the selected correction. Choosing Curves Layer, for example, displays the Curves dialog box. (Invert Layer is the only option that pro- duces no dialog box whatsoever.) Change the settings as desired and press Enter as you normally would. Regardless of the color adjustment you select, it appears as a new layer in the Layers palette. In Figure 17-31, for example, I’ve added a total of three adjustment layers. Photoshop marks adjustment layers with special icons that look like minia- ture versions of their respective dialog boxes. This way, you can readily tell them apart from image layers.