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Adjusting Color

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This chapter is from the book

Making Other Adjustments

As you've seen, Variations is the quick way to adjust color, but sometimes it doesn't give you enough control. Other times you just want to experiment. Maybe you have a picture that's mediocre, but if you play with the colors in it and beef up the contrast, you can make something out of it. These are the times when you'll want to work with individual adjustment settings.

Consulting the Histogram

Photoshop's Histogram palette was once a dialog box. It doesn't actually do anything by itself, but if you learn how to use it, you can save yourself lots of time. If you ever took a course in statistics, you already know that a histogram is a kind of graph. In Photoshop, it's a graph of the image reduced to grayscale, with lines to indicate the number of pixels at each step in the grayscale from 0 to 255.

You might wonder why this is important. The main reason is that you can tell by looking at the histogram whether there's enough contrast in the image to allow you to apply corrections successfully. If you have an apparently bad photo or a bad scan, studying the histogram will tell you whether it's worth working on or whether you should throw away the image and start over. If all the lines are bunched up tight at one end of the graph, and the image isn't supposed to be very dark or very light, you probably can't save the picture by adjusting it. If, on the other hand, you have a reasonably well-spread-out histogram, there's a wide enough range of values to suggest that the picture can be saved. Watch out for gaps in the middle of the graph, and for ends that cut off suddenly rather than tapering down to zero. Figure 5.4 shows the histogram for a reasonably well-exposed photo.

Figure 5.4

Figure 5.4 There are plenty of lights and darks in the picture this histogram represents.

The Histogram command has another use, which is to give you a sense of the tonal range of the image. This is sometimes referred to as the key type. An image is said to be low key, average key, or high key, depending on whether it has a preponderance of dark, middle, or light tones, respectively. A picture that is all medium gray would have only one line in its histogram, and it would fall right in the middle.

All you really need to know is that, when you look at the histogram, you should see a fairly even distribution across the graph, if the image is intended to be an average key picture. If the picture is high key, most of the lines in the histogram are concentrated on the right side with a few on the left. If it is low key, most of the values will be to the left with a few to the right.

Adjusting with the Levels Dialog Box

Adjusting levels is a method of changing the brightness of an image. As you can see in Figure 5.5, the Levels dialog box has a copy of the histogram, along with some controls that you can use to adjust the values.

Figure 5.5

Figure 5.5 Be sure to check the Preview box so that you can see the effect of your changes.

Setting the black point (the point at the left of the histogram that represents absolutely saturated black) to match the concentration of darkest levels in the image, and setting the white point (at the right, indicating completely unsaturated white) to match the concentration of the lightest levels in the image, forces the rest of the levels to reassign themselves more equitably. The photo I'm using in these examples happens to be quite dark, but there's still ample detail. (You can download the uncorrected image from the book's website; the file is called chinadoll.jpg.)

You can also use the Eyedroppers to adjust the levels. Click the white Eyedropper (on the right) and click the lightest part of your image. Then click the dark-tipped Eyedropper (on the left) to select it and click the darkest point on the image. If you're working on a grayscale image and there's an area in the image that seems to be right in the middle, click it with the midrange Eyedropper (in the middle). Avoid using the midrange Eyedropper in a color image unless it has an area that's supposed to be a neutral gray—neither reddish (warm) nor bluish (cool); if you click in an colored area, Photoshop will adjust all the image's colors so that the area you clicked in doesn't have any color.

Adjusting with the Curves Dialog Box

Adjusting curves is much like adjusting levels, although a bit subtler. You can use the Curves dialog box instead of the Levels dialog box to adjust the brightness. The big difference is that, instead of adjusting at only three points (black, middle, and white), you can adjust at any point (see Figure 5.7).

Figure 5.7

Figure 5.7 On this kind of graph, the zero point is in the middle.

When you open the Curves dialog box, you won't see a curve. Instead, you see a different kind of graph, one with a grid and a diagonal line. The horizontal axis of the grid represents the original values (input levels) of the image or selection, whereas the vertical axis represents the new values (output levels). When you first open the box, the graph appears as a diagonal line because no new values have been mapped. All pixels have identical input and output values. As always, be sure to check the Preview box before doing anything else so that you can see the effects of your changes.

As with the Levels dialog box, you can click Auto or use the Eyedroppers to adjust the values. Because the Curves method gives you so much more control, you might as well take full advantage of it. Hold down the mouse button and drag the cursor over the portion of the image that needs adjusting. You'll see a circle on the graph at the point representing the pixel where the cursor is. If there are points on the curve that you don't want to change, click them to lock them down. For instance, if you want to adjust the midtones while leaving the darks and lights relatively untouched, click the light and dark points on the curve to mark the points at which you want to stop making changes. Then, drag the middle of the curve until the image looks right to you. Dragging up lightens tones, whereas dragging down darkens them. Figure 5.8 shows what this actually looks like (this figure is also shown in the Color Gallery). To get rid of a point that you have placed, click and drag it off the grid.

Figure 5.8

Figure 5.8 You can add up to 16 points on the curve.

Adjusting with the Color Balance Dialog Box

To really understand color balance, you have to look at the color wheel. In case you don't remember the order of the color wheel, just flip to the Color Gallery and take a look at the example provided.

Every color on the wheel has an opposite. If you follow the line from one color through the center of the wheel, you reach its opposite. Cyan is opposite to red; green is opposite to magenta; and yellow is opposite to blue. When you use the Color Balance dialog box to adjust colors in a picture, you're adding more of the color opposite to the one you want to reduce. Increasing the cyan reduces red. Increasing red reduces cyan, and so on, around the wheel.

Figure 5.9 shows the Color Balance dialog box. Color Balance is intended to be used for general color correction rather than for correcting specific parts of an image, although you can use it that way by selecting only the part to correct. It's especially helpful if you have a scanned image that is off-color, such as an old, yellowed photograph. It's very simple to apply the Color Balance tools to remove the yellow without altering the rest of the picture.

Figure 5.9

Figure 5.9 Move the sliders in the direction of the color you want to add.

In addition to Color Balance, you can use the sliders to adjust tone balance. As with the Variations dialog box described earlier, you can concentrate your efforts on adjusting shadows, midtones, or highlights by clicking the appropriate button.

Adjusting with the Hue/Saturation Dialog Box

The Hue/Saturation dialog box is a very powerful tool with a slightly misleading name. Sure, it lets you adjust the hue (colors in the image) and the saturation (the intensity of the colors), but it also gives you control over the lightness.

First, look at the controls in the Hue/Saturation dialog box (see Figure 5.10). The first pop-up Edit menu lets you select either a single color to adjust or the Master setting, which adjusts all the colors in the image or selection at once. For now, work with the Master setting. Check Preview so that you can see the effects of your changes in the picture you're working on.

Figure 5.10

Figure 5.10 Small adjustments to Lightness and Saturation are usually all that's needed.

There are three sliders: Hue, Saturation, and Lightness. The Hue slider moves around the color wheel. With Master selected, you can move all the way from red (in the middle of the slider), left—through purple to blue or blue-green—or right through orange to yellow and to green.

The Saturation slider takes you from 0%, in the center, to 100% saturated (pure color, with no gray) on the right, or 100% unsaturated (no color) on the left.

The Lightness slider lets you increase or decrease the brightness of the image, from zero in the center, to +100 on the right, or –100 on the left.

As you move these sliders, watch the two spectrum strips at the bottom of the window, as well as the image itself. The upper strip represents the current status of the image, and the lower one changes according to the slider(s) you move. If you move the Hue slider to +60, for example, you can see that the reds in the picture turn quite yellow and the blues turn purple. In effect, what you are doing is skewing the color spectrum by that amount. If you move the Saturation slider to the left, you'll see the lower spectrum strip become less saturated. If you move the Lightness slider, you'll see its effects reflected in the lower spectrum strip as well.

Instead of selecting Master from the pop-up menu, if you select a color, the dialog box changes slightly, as you can see in Figure 5.11. The Eyedroppers are now active, enabling you to select colors from the image, and adjustable range sliders are centered on the color you have chosen to adjust. You can move these back and forth to focus on as broad or narrow a range within that color as you want. This might not seem like a big deal, but it's really very powerful, especially if you want to create a pink tiger, or maybe a blue one.

Figure 5.11

Figure 5.11 Click and drag to move the sliders. You can extend the range of colors to be affected by dragging the edges of the range selector between the two color bars.

Adjusting with the Brightness/Contrast Dialog Box

Photoshop CS3's Brightness/Contrast function isn't new, but it's definitely improved. If you need to make a simple adjustment to the tonal range of an image that scanned too dark, the Brightness/Contrast dialog box (choose Image>Adjustments>Brightness/Contrast) seems like an easy way to accomplish just that (see Figure 5.12), right? However, in all previous versions of Photoshop, Brightness/Contrast applied the same correction throughout the image, meaning that if you made the image brighter, you ended up with gray shadows and stark white highlights along with your nice, bright midtones. Now, however, that's all changed; Brightness/Contrast now separately corrects the dark, middle, and light values.

Figure 5.12

Figure 5.12 Use the sliders to adjust the brightness and contrast.

Although the Brightness/Contrast dialog box doesn't give you the same control that you would have if you made the adjustments using Levels or Curves, or even the Variations dialog box, it's quick and easy. Sometimes it's all you need. Many images are improved by just raising the brightness and contrast by a couple of points. As always, be sure to check the Preview box so that you can see the effect your changes have on the image.

Dragging the sliders to the right of the middle point increases brightness or contrast. Dragging them to the left decreases it. If you're not happy with the results you get with this tool, undo your changes and use the Variations dialog box, or Levels or Curves, to adjust the brightness and contrast.

If you encounter a situation in which you want to make everything in your picture lighter or darker, you can revert temporarily to the old version of the Brightness/Contrast function by clicking the Legacy check box.

Correcting the Shadows and Highlights

One of the coolest features in Photoshop is the Shadow/Highlight dialog box. It allows you to control the amount of highlight and shadow on an image without changing the contrast. If you apply it to the tiger photo, you can let her sit in deeper shade without changing the intensity of her stripes, or turn up the sunlight without washing the color out of her pale cream fur. Be sure to check the Show More Options box to open the full set of sliders, as shown in Figure 5.13. See the corrected tiger in Color Plate 5.12, and compare her to the original picture in Color Plate 5.6.

Figure 5.13

Figure 5.13 Experiment with these sliders on both high-contrast and low-contrast images.

Photo Filters

When a photographer wants a special effect, he or she might use a colored filter over the camera lens. With this feature, you can do the same thing to any image, whether from a camera, scanned, or created from scratch. In Figure 5.14, I have expanded the list of filters so you can see the many options available. Serious photographers will recognize the numbers after the warming and cooling filters, because they are the same as on the glass filters you might buy at a good camera store. Use the slider to control the strength of the filter. Typically, you would use no more than 10–20% to warm up daylight or to take the excess yellow out of an indoor shot. To open the Photo Filter dialog box, follow this path: Image>Adjustments>Photo Filter.

Figure 5.14

Figure 5.14 You can also use any color as a filter.

Other Menu Options

It's almost time to wrap up your tour of the Adjustments submenu. Here's a look at a few commands we haven't covered yet that you might find useful.

Auto Contrast is occasionally helpful. It automatically maps the darkest and lightest pixels in the image to black and white, causing highlights to appear lighter and shadows darker. It might not be the best way to make the necessary adjustments, but, if you are in a hurry, it can save you some time.

There's another Auto tool: Auto Color. This tool, quite simply, analyzes the color in an image and makes an educated guess as to what it should be. If you're easily satisfied, it might be all the correction you ever need. As for me, I like things perfect, and Photoshop's sense of color is often different than mine.

Desaturate removes all of the color from an image, without changing the color mode. If you want a quick look at how something will reproduce in black and white, this is the command to use. Then, simply undo it to go back to the colored version.

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