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### Laying the Groundwork for Applying Curves

In this chapter, we introduce you to Curves and provide you with a solid foundation on which you can build your expertise through practice with color correcting. Before you start working with the examples, though, take a moment to read through some of the groundwork upon which this chapter is built, so you'll have a better idea of where you're going and what you'll learn from the exercises. Here's a list of some of the basic principles and guidelines you should keep in mind when working through the exercises in this chapter:

• The discussion and sample images are limited to the RGB color space (most of our readers use RGB). Although the basic principles of using Curves apply to all color spaces, the characteristics of each color space deserve a study beyond the scope of one chapter. The RGB color space is big enough for all-purpose work and is ideal for digital images. If you plan to output your images (film, print, and so on), you might find the need to develop a different approach to correcting color than what is suggested here.

• The goal of color correcting is to improve the image's tonal range and color, not to reproduce the actual colors at the scene or of the scanned photograph. We don't always know or remember the actual colors in the scene. Say, for example, I shot a picture of a spectacular sunset with my royal blue yacht in the foreground, and you offer to color correct the scan of the image. You know that the boat is royal blue; therefore, you make it royal blue. But I disagree with the red in the sky; it's not the hue of red that I saw. Because you have no way of knowing the true colors in the scene, you correct for the known color(s) and move the rest into an acceptable range.

• You'll use two methods to determine the Curves adjustments: numerical values of specific areas in the image (using the Eyedropper and the Info palette) and what the colors look like on your monitor. Each method is acceptable, depending on the intended use of your photo. For example, if you will view a particular image only on your monitor, correct the colors as you see them on your monitor.

• Each of the six stepped procedures in this chapter uses a different image, and each image contains its own unique problems. The solutions to those problems progress from a basic correction to more advanced techniques.

• Making numerous trips to the Curves command to correct numerous images is the best way to learn how to use Curves. As the story goes, a tourist in New York City asked a native how to get to Carnegie Hall. The response was, “Practice, practice, practice.”

• Using Photoshop's Adjustment Layers is the preferred method for making image corrections. An Adjustment Layer works like a filter on a camera lens, and the corrections are placed into this layer, leaving the original pixels unchanged. Each change you make to the original pixels degrades the quality. Adjustment Layers also allow you to modify your settings indefinitely, without harming innocent pixels.

• The Adobe 1998 profile is the preferred default color space for all-around, general-purpose imaging work. When you're working with the files in the Examples/Chap12 folder, if you receive a Mismatching Profile message box, press Ctrl()+Shift+K, and change the RGB Working Space to Adobe RGB 1998. Then, in the Color Management Policies section, make sure Preserve Embedded Profiles is the choice in all drop-down boxes. Also, make sure all the Ask When Opening check boxes are unchecked. See Chapter 2, “The Critically Important Color and Gamma Calibration Chapter,” for more information on the Adobe 1998 profile.

Warning

Producing histograms If you want to produce accurate histograms, we strongly recommended that you uncheck the Use Cache for Histograms option in the Memory & Image Cache section of Photoshop's Preferences. Using the cache to calculate histograms (used in commands such as Variations, Levels, and Curves) is a quick but much less precise method of producing histograms. Unchecking this preference setting makes histograms more accurate!

• Perception of color can be very subjective. All of us are influenced by personal preferences and our own ability to perceive colors, so you might not agree with some of the color settings given in the exercises. You might see a particular yellow that you would describe as a traffic-light yellow, whereas someone else might see it as a lemon yellow. You might prefer the colors in a photograph to have a pastel quality, whereas the guy next to you might prefer bold, fully saturated colors. We address the issue of individual color perception and how Photoshop CS evaluates color in “Using the Color Sampler Tool,” later in this chapter.

• An image tends to look complete if it has a full range of tones from black to white. Without a black point and white point, the photo will look flat—lacking contrast. There can be exceptions to this rule, but this is the philosophy we'll adopt when correcting most of the photos in this chapter. To achieve that “complete” look in our photos, we'll take these steps:

• Correct for the known colors.

• Adjust the remaining colors to fit into an acceptable range.

• Create a full range of tones.

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