Tài iệu Photoshop cs5 by Dayley part 122 pdf

C H A P T E R Printing and Color Management IN THIS CHAPTER Understanding color management Embedding color profiles in images Color calibrating devices Configuring color management in P

Part IX

Advanced Output

Techniques

IN THIS PART

Chapter 29

Printing and Color Management

Chapter 30

Creating Images for the Web and Mobile Devices

Chapter 31

Digital Workflow and Automation

C H A P T E R

Printing and Color

Management

IN THIS CHAPTER

Understanding color management Embedding color profiles in images

Color calibrating devices Configuring color management in Photoshop Hard and soft proofing images for different devices

Using color management to print accurate colors Adding crop marks when printing images

Color is one of the most important aspects in digital images In fact,

the look of most images is completely dependent upon the color composition Unfortunately, color is not consistent as you move from device to device, so it is difficult to guarantee that the color corrections

you make on one computer will match what you see on another or when the

image is printed out

Color management solves these problems by assigning color profiles that

describe the colors in a device and then using those profiles to convert the

image data as it is transferred from device to device This chapter discusses

color management and how Photoshop uses it to ensure the colors in your

images are consistent as they are transferred to other devices and printed

Importance of Color Accuracy

and Consistency

Few things are more frustrating that spending hours editing an image only to

find out that the finished product looks terrible when you print it

Differences in monitor quality and even just the age difference between two

monitors can result in severe variations in color in images Additionally,

differences in printers, ink, and paper also result in a high variance of color

output A good color management workflow helps you overcome these

problems and gives you the best chance of matching the edited color with

the final results when the image is outputted

The following list describes a good color management workflow that helps

you ensure accuracy when editing, distributing, and outputting image:

Part IX: Advanced Output Techniques

1 Calibrate your monitor using either a software application or a hardware calibration

device

Because the pixels in your monitor fade with age, you may need to calibrate your monitor monthly or at least at the start of any big projects

2 Add color profiles that describe how color will appear on the output devices you

are using

Output devices can be specific monitors, portable devices, or printers

3 Set up color management in the Adobe software

Photoshop provides proofing options to preview the way that images will appear when they are outputted

4 Save the color management data with the edited document

This ensures that the edited document will contain the information you expect to use to output the image

Understanding ICC color profiles

Color profiles mathematically define the way that a device interprets the level values that define color in an image ICC (International Color Consortium) color profiles define the gamut (range) of colors that a device is capable of reproducing, because not all devices can produce the same color ranges

Color Management Modules (CMMs), also called Color Matching Modules, like Apple’s ColorSync and Microsoft’s Windows Color System (WCS), utilize the ICC color profiles to match or convert the color levels between input and output sources CMMs work by utilizing the source ICC color profile provided along with the original file and the destination ICC color profile for the output device to convert the colors in the original file to the appropriate values that will give the most consistent color result in the output

ICC profiles are typically provided by hardware manufacturers of the monitors, printers, and other devices Although these files are typically good enough for most needs, you also may want to develop your own profiles that take into account factors such as ambient lighting in your workspace, age of the monitor, and other variable conditions Many high-end printing facilities provide profiles that allow you to accurately preview the final output from Photoshop before delivering the finished documents

Embedding color profiles in image files

ICC profiles can be embedded into most of the common image file types, such as PSD, JPEG, EPS, TIFF, and PSB Embedding the color profiles inside the actual document ensures that the images are displayed correctly when they are transferred between different devices

To embed a color profile in an image, simply select the ICC Profile option, shown in Figure 29.1, when you use the File ➪ Save As option from the main menu in Photoshop The ICC Profile option displays only if you have added a color profile to the image and if the image file type supports color profiles

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FIGURE 29.1

Embedding a color profile in an image is done by selecting the ICC Profile option in the Save As

dialog box

You also can embed a color profile in an image when you are using the File ➪ Save for Web

& Devices option When you select a file type that supports color profiles in the Save for Web &

Devices dialog box, the embed color profile option is available

Note

Most images automatically use the sRGB color profile because the Web is the most common outlet of images,

and that is the profile used for Web production n

Device-independent color profiles

A problem can occur with CMMs using the ICC color profiles: The RGB and CYMK colors can vary between different devices That means you can get inaccurate translation between the two color modes

To solve that problem, the Commission Internationale d’Elairage developed a set of device-independent color models The CIE XYZ and CIE LAB color spaces are two of those device-independent color models These color spaces are used as interim spaces when converting between the different color models

Part IX: Advanced Output Techniques

Color Calibrating Monitors and Printers

The most important step in color management is to calibrate the monitor on the computer where you are editing images Without the monitor calibrated, you could end up spending hours to get the perfect color tones in the image only to find that your monitor was off and the colors don’t really look that good elsewhere

Two methods are used for calibrating a monitor The simplest, although least accurate, is to use software to manually adjust the gamma, brightness, contrast, and color that the system uses for the display On Windows 7 systems, you can calibrate the monitor by selecting Start ➪ Control Panel ➪ Hardware and Sound ➪ Display ➪ Calibrate Color to bring up the calibration utility shown

in Figure 29.2 On Apple systems, you can calibrate the monitor by using the Display Calibrator Assistant found in the Displays pane of the System Preferences

The most accurate method of calibrating a monitor is to attach a device called a calorimeter flat to the display surface The calorimeter and display must be shielded from all ambient light Then calibration software that comes with the calorimeter sends a series of color signals to the display and compares the values seen by the calorimeter with known expected values This establishes the current offsets in the color display, and ICC profiles can be created and the display’s brightness, contrast, and RGB settings can be adjusted

FIGURE 29.2

Calibrating color on the display in Windows is a process of adjusting the gamma, brightness, contrast, and

colors

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Because ink and paper quality affect printer output so much, you cannot adjust the settings on a printer to calibrate color output Instead, printers use ICC profiles that are created by printing a test sample with known output gamma, brightness, contrast, and color outputs The sample test print is then analyzed by a photometer (sometimes called a spectrophotometer) to determine the actual output with known CYMK colors Software that comes with the photometer then uses the difference between the two to create the ICC profile Although the cost of the photometer and software is expensive, you can typically find an ICC profile for your printer/ink combination on the Internet for reasonable prices (usually about $20–$30)

Using Color Management in Photoshop

Now that we have discussed the theory of color profiles, you are ready to configure and use the color management settings in Photoshop The following sections discuss how to configure the color management settings in Photoshop, assign color profiles to images, and proof images using different color profiles

Configuring color settings in Photoshop

The color settings in Photoshop are configured using the Color Settings utility, shown in Figure 29.3

Launch the color settings dialog box by pressing Ctrl/Ô+Shift+K on the keyboard or selecting Edit ➪ Color Settings from the main menu At first appearance, the dialog box may seem a bit unfamiliar and daunting The next few sections discuss each of the options available in the Color Settings dialog box and hopefully dispel any apprehension of using them

Tip

If you save your color settings as a preset file, you can use that preset in Adobe Bridge’s Suite Color Settings

dialog box (launched by pressing Ctrl/Ô+Shift+K in Bridge) Bridge’s Suite Color Settings utility allows you to

synchronize the color management profiles between Creative Suite applications n

Settings

The Settings menu option offers a list of preset color configurations that set the color options for the workspace and management policies for general purposes If you really don’t want to take the time to set up your own custom color configuration, you can use one of these presets The presets list contains presets for North America, Europe, and Japan that fall into the following categories:

l Monitor Color: Use this setting if you plan to use the images in a video or onscreen

presentation This setting uses the Monitor RGB option, which uses the current monitor’s color space and in effect acts like color management is turned off in Photoshop

l General Purpose: Use this setting if you need to use the image for both print and

onscreen viewing This setting uses the sRGB color profile that best supports most monitors

as well as the U.S Web Coated (SWOP) v2 color profile for CYMK that works well for printing