Tài iệu Photoshop cs5 by Dayley part 123 pdf

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.. Working Spa

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

FIGURE 29.3

The Color Settings dialog box allows you to configure the color workspaces and the color management

policies

l Newspaper: Use this setting for images that are intended for output to newspaper The

CYMK workspace is set to U.S Newsprint, and the Gray and Spot colors are set to use a

25 percent Dot Grain that works well for printing to newspaper-type material

l Prepress: Use this setting for images that are intended for output to a printer The RGB

workspace is set to Adobe RGB, which provides a good range of colors for printing; the CYMK workspace is set to U.S Web Coated (SWOP) v2, which works generally well for printing

l Web/Internet: Use this setting for images that are intended to be displayed on the Web

This option sets the RGB workspace to sRGB, which is the best for supporting a variety of computer monitors; the Gray workspace is set to Gray Gamma 2.2, which works best for displaying grayscale images on a variety of monitors

You also can save any custom configuration that you define using the Save button and then load it later, even on another computer, by hitting the Load button

Working Spaces

The Working Spaces settings allow you to configure the ICC color profiles that the RGB, CYMK, Grayscale, and Duotone models use to display the images on your display while you are editing them Using the appropriate color model helps you edit and adjust your images so they look as good as possible when they are viewed on the output medium

The following list describes some of the profiles available in each of the workspaces:

l RGB: Although there are many RGB color profiles, you likely will work with only two or

three The most common ones are the Adobe RGB and the sRGB IEC61966-2.1 (sRGB)

The difference between the two is that the sRGB has reduced the gamut of colors it allows around the outer edges This reduces the number of colors that can exist in the image so the colors are supported on the widest range of computer displays possible That way, the image looks exactly the same on all displays

Another RGB color profile you may end up using is the Monitor RGB It sets the RGB working space to the current monitor space, which causes Photoshop to behave as if color management was turned off This is actually handy if you are outputting the images to a medium that doesn’t support color management, such as a video or a presentation application

l CYMK: The CYMK color model is typically used for printed images Therefore, each of

the available CYMK color profiles actually corresponds to a specific ink and paper combination When you convert an image from RBG to CYMK using the Image ➪ Mode ➪ CYMK color option, the CYMK color profile is used as a basis for the conversion between the two color models

The most common profile you will use is U.S Web Coated (SWOP) v2 Other color profiles may be provided by your printing press or by a printer manufacturer

l Gray: The Gray color profiles define the dot grain used to display images converted into

grayscale using the Image ➪ Mode ➪ Grayscale option There are two basic options: One is

to set the percent of dot grain, and the other is to use a gamma option that uses the gamma setting of your monitor to define the brightness of the midtones in the grayscale image The most commonly used gamma option is Gray Gamma 2.2 because it supports most of the current monitors

l Spot: This specifies the dot grain to use when displaying spot color channels and duotones.

Color Management Policies

The Color Management Policies section of the Color Settings dialog box provides control over how Photoshop manages the RGB, CYMK, and grayscale images that are opened Many images already contain ICC color profiles embedded in them, and the settings in this panel allow you to define how Photoshop uses those files in relation to the color profiles defined in the Working Spaces section

For each of the three color modes, you can set the following options:

l Off: When Off is selected, color management is disabled in images that you open or

create If you open an image with an embedded color profile, the color profile is ignored

You should be careful if you use this option while copying and pasting from one image to another, because although the color data is preserved, the colors may look different

l Preserve Embedded Profiles: This is the default option and is the best option to ensure

the most consistent colors between images that are edited on different computers When

l Convert to Working Profile: When this option is selected, Photoshop uses the color

profile in the image to convert the data in the image to use the working color profile The working color profile is then embedded in the image when it is saved

The Color Management Policies also provide check boxes that allow you to turn on dialog boxes that pop up if you open or paste data into an image that has a color profile embedded that mismatches the working profile or is missing The dialog box warns you and allows you to determine at that time how to handle color management for that image, as shown in Figure 29.4

FIGURE 29.4

Enabling the Ask When Opening and Ask When Pasting options in the Color Settings dialog box presents

notifications that allow you to handle images that either do not have an embedded color profile or have a

color profile that does not match the current working color space

Note

Photoshop allows you to open multiple images that use different color profiles This can be useful if you are

working on projects with images that are destined for different outputting However, you should be careful if

you need to share pixels between images—for example, cutting and pasting or selecting colors from one image

that you want to be used in another image or sharing channels n

Conversion Options

Photoshop also provides control over conversion between color profiles when you click the More Options button in the Color Settings dialog box Figure 29.5 shows the Conversion Options and the Advanced Controls settings

FIGURE 29.5

The More Options button extends the Color Settings dialog box and allows you to configure conversion

and advanced controls for color management

In the Conversion Options section, you can configure the following options:

l Engine: This allows you to specify the CMM that will be used to manage conversion

between color profiles Typically, you have two options: Adobe ACE is provided by Adobe and is available on both Windows and Apple; the other option is the default CMM that is provided with your operating system—for example, Microsoft ICM on Windows or Apple CMM on Apple

l Intent: This option allows you to select one of the following options that determine how

the CMM interprets colors between color spaces:

l Perceptual: When this option is selected, all colors in the source color profile are

compressed to fit in the destination color profile’s gamut Neighboring pixels are taken into consideration so the colors are adjusted proportionally This provides a better perceptual translation because the relationship between the pixel and its neighbors is more important than finding the closest matching color

l Saturation: When this option is selected, colors in the source color profile that do not

exist in the destination color profile’s gamut are changed to the closest color value in the destination color profile without considering neighboring pixel values This can result in a color shift that increases saturation in the image Typically, this option is used only for images with lots of solid colors and not for photographs

l Relative Colorimetric: When this option is selected, colors are translated between

profiles by mapping white in the source color profile with white in the destination color profile and then using that mapping to adjust the rest of the colors This option usually works very well; however, if you are converting a smaller color space to a larger color space (CYMK to RGB, for example), a banding and dithering effect can result in the darker areas of the image

l Absolute Colorimetric: When this option is selected, Photoshop maps the colors

between the two spaces by mapping between the absolute lab coordinates in each color profile This option is used for hard proofing and simulating output on a specific printer

l Use Black Point Compensation: This simulates the entire dynamic range of the printer

to ensure that the shadow details in the image are preserved This option should be selected if you plan on using black point compensation when printing the image

l Use Dither: When this option is selected, Photoshop mixes colors in the destination color

profile to simulate colors in the source color profile This helps reduce blocky and banding artifacts that can otherwise occur

l Compensate for Scene-referred Profiles: This compares the video contrast when

converting from scene to output color profiles, similar to color management in After Effects This option is specific to working with video files in Photoshop

Advanced Controls

In addition to the Conversion Options described in the previous section, Photoshop provides more Advanced Controls options when the More Options button is clicked In the Advanced Controls section, you can configure the following options:

l Desaturate Monitor Colors By: This specifies a percentage to desaturate colors when

they are displayed on the monitor Selecting this option helps you visualize the full range

of color spaces with a similar gamut of the monitor However, this can result in color mismatches between monitor display and output Deselecting this option can result in two distinct colors appearing as the same color on the monitor

l Blend RGB Colors Using Gamma: This controls how RGB colors in the image are

blended together to produce composite data, such as blending layers or painting Selecting this option blends the RGB colors in the color space based on the gamma setting specified

A gamma of 1.00 is considered “colorimetrically correct” and likely provides the fewest edge artifacts

Note

When you use Blend RGB Colors Using Gamma, layered documents look different when viewed in other

applications than they appear in Photoshop n

Assigning color profiles to images

Photoshop allows you to assign color profiles to images If the image already contains an embedded color profile, that color profile is replaced with the newly assigned color profile, but the level values in the image do not change

To assign a color profile to an image, open the image in Photoshop and select Edit ➪ Assign Profile from the main menu A dialog box similar to the one shown in Figure 29.6 is displayed, and you can set the following options:

Caution

Because layer adjustments, filters, and blending modes are based on the original colors, assigning a color

profile to the image may alter the appearance of the layers You should always assign a color profile to the

image before you begin editing it if possible n

l Don’t Color Manage This Document: This removes any color profiles from the document

that currently exist, and Photoshop displays the image according to the current working color space

l Working [Color Model] [Color Profile]: This adds the current working color profile to

the image and uses that profile to display it while editing

l Profile: This allows you to select a color profile from a drop-down list that is embedded

in the image Which color profile is used to display the image depends on the color management settings described earlier

FIGURE 29.6

Using the Edit ➪ Assign Profile option, you can add a color profile to an image or replace the currently

embedded color profile

Converting images to other color profiles

Photoshop allows you to convert images from one color profile to another If the image already contains an embedded color profile, you likely want to keep the colors intact when moving from one profile to the next Converting color profiles uses the color profile in the image to convert the color levels to match a new color profile and then embeds the new color profile in the image

To convert an image from one color profile to another, open the image in Photoshop and select Edit ➪ Convert to Profile from the main menu A dialog box similar to the one shown in Figure 29.7 is displayed Clicking the advanced option expands the dialog box; you can set the following options:

l Source Space: This displays the source color space that was already embedded in the

image

l Destination Space: In the basic dialog box, this option allows you to select the ICC

profile to convert the image In the Advanced dialog box, this option allows you to select the color mode and color profile to use when converting the image This option often is a better method to change the color mode because it gives you direct control over both the color mode and color profile

l Conversion Options: The Engine, Intent, Use Black Point Compensation, and Use Dither

options were discussed earlier in this chapter The Flatten Image to Preserve Appearance option is provided to overcome the problem of blending layers The problem with blending layers is that converting the layers individually and then flattening results in a different pixel color than flattening first and then converting This can be a tough choice if you are relying on using the layers later

FIGURE 29.7

Using the Edit ➪ Convert to Profile option, you can use the currently embedded color profile in an image

to convert the image to another color profile and embed that color profile

Proofing images using color management

In addition to embedding color profiles in images and setting the working color management set-tings, Photoshop provides quick proofing of images to see how they will appear in some of the

common color profiles This process is known as soft proofing.

To set up the proofing color space, select View ➪ Proof Setup and then select the color space from the main menu The selected color space is used when proofing Selecting View ➪ Proof Setup ➪ Custom displays the Customize Proof Condition dialog box, shown in Figure 29.8, where you can set the following customized color proofing options:

l Device to Simulate: This allows you to select the color or device profile to use when

proofing the colors in the image