Sử dụng photoshop cs5 part 1 ppsx

16 1 ter, you’ll launch the application and familiarize yourself with Photoshop color basics, such as displays, docu-ment color modes, and channels.Most important, before you start ed

IN THIS CHAPTER Launching Photoshop 1 Displays, modes, and channels 2 Introduction to color management 5 Setting a camera’s color space to Adobe RGB 5 Calibrating your display 7 Choosing a color space for

Photoshop 10 Synchronizing color settings 12 Customizing your color policies 13 Saving custom color settings 14 Acquiring printer profi les 14 Changing color profi les 16

1

ter, you’ll launch the application and

familiarize yourself with Photoshop

color basics, such as displays,

docu-ment color modes, and channels.Most

important, before you start editing images — and

also before outputting any files — you need to

incor-porate color management into your workflow You’ll

accomplish this by calibrating your display, choosing

color settings, and downloading the necessary printer

profiles

Launching Photoshop

To launch Photoshop in Windows:

Do one of the following:

In a 32-bit version of Windows, click the Start button

on the taskbar, choose All Programs, then click Adobe

Photoshop CS5

In a 64-bit version of Windows, click the Start button,

choose All Programs, then click Adobe Photoshop CS5

(64-bit)

Double-click a Photoshop file icon

To launch Photoshop in the Mac OS:

Do one of the following:

Click the Photoshop icon in the Dock (If you

haven’t created the icon yet, open the Adobe

Photoshop CS5 folder in the Applications folder, then

drag the Adobe Photoshop CS5 application icon into

the Dock.)

Open the Adobe Photoshop CS5 folder in the

Applications folder, then double-click the Adobe

Photoshop CS5 application icon

Double-click any Photoshop file icon

WANT TO SEE MORE ONSCREEN?

If you want to open a fi le quickly to make the screen

more “live” as you read through this chapter, navigate

to the Samples folder inside the Photoshop

applica-tion folder, then double-click a psd image fi le, such

as “Fish.psd.” (Don’t worry…you’ll soon learn how to

open photos and create documents.)

FINDING THE NEW STUFF

This symbol ★identifi es Photoshop features that are

new or improved

variables as the temperature of the display, the lighting in the room, and even the colors on your wall Moreover, many colors that you see in the natural world or that can be displayed onscreen can’t be printed (have no ink equivalents), and conversely, some printable colors can’t be displayed onscreen The color management techniques that

we outline in this chapter will help smooth out the kinks in the color workflow from digital input to display onscreen, then finally to print

➤ In Photoshop, you can choose colors using the Grayscale, RGB (red-green-blue), HSB (hue-saturation-brightness), CMYK (cyan-magenta-yellow-black), or Lab (lightness, a-component, and b-component) color model, and you can choose colors from a color matching system, such as PANTONE

Photoshop channels

All Photoshop images are composed of one, three,

or four channels (see the sidebar below) In an RGB image, for example, the three channels store the intensity of red, green, or blue at each pixel

as a level of gray Most likely you will work with images that store 256 levels of gray for each chan-nel Because the 256 gray levels are represented by

8 bits (short for “binary digits”) of computer data, the bit depth of such an image is said to be 8 bits per channel Files that have a higher bit depth of

16 or 32 bits per channel contain more color infor-mation (see page 19)

➤ Open an RGB Color image and display the Channels panel Click Red, Green, or Blue

on the panel to display only that channel, then click the topmost channel name on the panel

to restore the composite display Although you

Displays, modes, and channels

Onscreen, your Photoshop image is a bitmap —

a geometric arrangement, or mapping, of dots on

a rectangular grid Each dot, or pixel, represents a

different color or shade If you drag with a painting

tool, such as the Brush, across an area of a layer,

pixels below your pointer are recolored With a

high zoom level chosen for your document, you can

see (and edit) individual pixels.A Bitmap programs

like Photoshop are best suited for editing and

pro-ducing photographic, painterly, or photorealistic

images that contain subtle gradations of color,

which are called “continuous tones.” The images

you edit in Photoshop can originate from a digital

camera, from a photo print that you have scanned,

from a file saved in another application, or from

scratch using program features, such as painting

and cloning tools

To enable color images to be viewed onscreen,

your display projects red, green, and blue (RGB)

light Combined in their purest form, these

addi-tive primaries produce white light If you were to

send your Photoshop file to a commercial print

shop for four-color process printing, it would be

rendered with cyan (C), magenta (M), yellow (Y),

and black (K) inks Because computer displays use

the RGB model, they can only simulate the CMYK

inks that are used in commercial printing

The successful translation of a digital image to a

printed one isn’t as simple as you might think To

begin with, the same document may look

surpris-ingly different on different displays due to such

A In this extreme close-up of a photo in Photoshop, you

can see the individual pixels that the image is made of.

DEFAULT NUMBER OF CHANNELS FOR EACH IMAGE MODE

Grayscale Lab Duotone Multichannel Multichannel Indexed Color

can make adjustments to individual channels,

normally you will edit all the channels at once

while viewing the composite image

In addition to the core channels we just discussed,

you can add two other types of channels You can

save a selection as a mask in a grayscale (alpha)

channel, or add channels for individual spot

colors.A

The more channels a document contains, the

larger its file storage size is A document in RGB

Color mode, which contains three channels (Red,

Green, and Blue), will be three times larger than

it would be if converted to Grayscale, a

single-channel mode If you were to convert it to CMYK

Color mode, the file would contain four channels

(Cyan, Magenta, Yellow, and Black) and would be

larger still

Photoshop document color modes

A document can be converted to, displayed in,

and edited in any of these color modes: Bitmap,

Grayscale, Duotone, Indexed Color, RGB Color,

CMYK Color, Lab Color, or Multi channel The ones

you will work in the most are RGB Color and CMYK

Color To convert a document to a different mode,

use the Image > Mode submenu B If a mode is

dimmed on the menu, it means you must convert

B Use the Mode submenu to change the color mode of your document.

Continued on the following page

A An alpha channel A spot color channel

Main image channels

the file to a different mode first in order to make it available For example, a file must be in Grayscale mode to be converted to Duotone mode The avail-ability of some Photoshop commands and options will vary depending on the color mode of your document

Some mode conversions can cause noticeable color shifts For example, if you convert a file from RGB Color mode to CMYK Color mode, printable colors will be substituted for RGB colors The fewer times you convert a file, the better, as its color data is altered with each conversion change Some conversions flatten layers, such as a conversion

to Indexed Color, Multichannel, or Bitmap mode

Other conversions give you the option to preserve layers via a Don’t Flatten button in an alert dialog

Digital cameras and medium- to low-end scan-ners produce RGB images For faster editing, and in order to access all the filters in Photoshop, we rec-ommend keeping your files in RGB Color mode In fact, most desktop color inkjet printers, especially those that use six or more ink colors, can process RGB Color files directly from Photoshop

➤ To “soft-proof” your RGB document as a simu-lation of CMYK Color mode without perform-ing an actual mode change, see pages 404–405

details), the colors green to red, and the colors blue to yellow The lightness and color values can

be edited independently of one another Although Photoshop uses Lab Color to produce conversions between RGB and CMYK color modes internally, there’s rarely a need for Photoshop users like us to convert our files to Lab Color mode

Multichannel images contain multiple 256-level

grayscale channels If you convert an image from RGB Color to Multichannel mode, its Red, Green, and Blue channels are converted to Cyan, Magenta, and Yellow As a result, the image may become lighter and the contrast may be reduced Some Photoshop pros assemble individual channels from several images into a single composite image by using this mode, but this takes expertise

With this foundation in color basics, you’re ready to take the plunge into color management

The following is a brief summary of the color

modes that a document can be converted to in

Photoshop:

In Bitmap mode, pixels are either 100% black or

100% white, and no layers, filters, or adjustment

commands are available (To convert a file to this

mode, you must convert it to Grayscale mode first.)

In Grayscale mode, pixels are black, white, or

up to 254 shades of gray (a total of 256) If you

convert a file from a color mode to Gray scale mode

and then save and close it, its luminosity (light and

dark) values will be preserved, but its color

infor-mation will be deleted permanently In Chapter 13,

we’ll show you how to convert a layer to grayscale

without changing the document color mode

To produce a duotone, two or more extra plates

are added to a grayscale image to enhance its

rich-ness and tonal depth This requires special

prepara-tory steps in Photoshop and expertise on the part

of your commercial printer

Files in Indexed Color mode contain a single

channel, as well as an 8-bit color table (which

con-tains a maximum number of 256 colors or shades)

When you optimize a file in the GIF format via

the Save for Web & Devices dialog, the file is

con-verted to this color mode automatically (see pages

423–424)

and the one you’ll use most often It’s the mode in

which digital cameras save your photos, the only

mode in which all the Photoshop tool options and

filters are accessible, the mode of choice for online

output, and the mode of choice for export to video

and multimedia programs

In Photoshop, although you can display and edit

your files in CMYK Color mode, Bwe recommend

editing them in RGB Color mode, then converting

a copy of them to CMYK Color mode only when

required for commercial printing or for export to

a page layout application Exceptions to this rule

are images that are saved by high-end scanners

in CMYK Color mode; keep them as CMYK to

preserve their original color data

Lab Color is a three-channel mode that was

developed for the purpose of achieving

consis-tency among various devices, such as printers and

displays Lab Color files are device-independent,

meaning their color definitions stay the same

regardless of how each output device defines

color The channels represent lightness (the image

A Because the mode of this document is RGB Color, it contains three channels.

B We converted the document to CMYK Color mode; now it contains four channels.

Introduction to color management

Problems with color inconsistency can arise due

to the fact that hardware devices and software

packages read or output color differently If you

were to compare how an image looks in an

assort-ment of imaging programs and Web browsers, the

colors might look completely different in each case,

and worse still, may not match the picture you

originally shot with your digital camera Print the

image, and you’ll probably find the results are

dif-ferent yet again In some cases, these differences

might be slight and unobjectionable, but in other

cases such color shifts can wreak havoc with your

design or turn a project into a disaster!

A color management system can prevent most

color discrepancies by acting as a color interpreter

It knows how each particular device and program

interprets color, and adjusts those colors when

necessary The result is that the colors in your files

will display and output more consistently as the

files are shuttled among various programs and

devices Applications in Adobe Creative Suite 5 use

standardized ICC (International Color Consortium)

profiles, which tell your color management system

how each specific device defines color

Each particular device ca n capture and

repro-duce only a limited range (gamut) of colors, which

in the jargon of color management is known as

the color space The mathematical description of

the color space of each device, in turn, is called

its color profile Furthermore, each input device,

such as a camera, attaches its own profile to the

files it produces Photoshop will use that profile in

order to display and edit the colors in your

docu-ment; or if the document doesn’t contain a profile,

Photoshop will use the current working space (a

color space you choose for Photoshop) instead

Color management is especially important when

the same image is used for multiple purposes, such

as for online output and print output Note: For

print output, be sure to consult with your prepress

service provider or commercial printer (if you’re

using one) about color management to ensure that

your color management setup works smoothly with

theirs

The “meat” of this chapter consists of instruc-tions for choosing color management opinstruc-tions, which we strongly recommend you follow before editing your images in Photoshop Our instructions are centered on using Adobe RGB as the color space for your image-editing work to create color consis-tency throughout your workflow We’ll show you how to set the color space of your digital camera to Adobe RGB, calibrate your display, specify Adobe RGB as the color space for Photoshop, acquire the proper profiles for your inkjet printer and paper type, and assign Adobe RGB as the profile of choice for files that don’t use that color space

You’ll need to focus on color management again when you prepare your file for printing In Chapter

25 (Print), you will create a soft-proof setting for your particular inkjet printer and paper using the acquired profiles, and then use it to view a soft proof of your document onscreen The profile will also be used for outputting files to a color inkjet printer, a device that expects files to be in RGB color Finally, we’ll show you how to use the appro-priate profiles when outputting either to the Web

or to a commercial press

The first step in color management is to estab-lish Adobe RGB as the color space for your camera

Setting a camera’s color space to Adobe RGB

Most high-end, advanced amateur digital cam-eras and digital SLR camcam-eras have an onscreen menu, which you can use to customize how the camera processes digital images Although we’ll use a Nikon D700 as our representative model for setting a camera to the Adobe RGB color space, you can follow a similar procedure to set the color space for your camera

Note: If you shoot photos in the JPEG format, you should choose Adobe RGB as the color space for your camera, regardless of which model it is If you shoot raw files, these steps are optional, as you will have the opportunity to assign the Adobe RGB color space when you convert your photos via the Camera Raw plug-in (see page 66)

Continued on the following page

To set a camera’s color space to Adobe RGB:

1 On the back of your Nikon camera, press the

Menu button to access the menu on the LCD

screen, and then, if necessary, press the up or

down arrow on the multi selector to select the

Shooting Menu tab.

2 On the Shooting Menu, press the down arrow

on the multi selector to select the Color Space

category A (Canon EOS Rebel cameras label this

category as Parameters) Press the right arrow

on the multi selector to move to the submenu

then press the Menu button to exit the Menu

screen

B We pressed the right arrow, then chose Adobe RGB from the Color Space submenu.

A On the Nikon Shooting Menu, we selected the

Color Space category.

NIKON D700

C After pressing OK, the Color Space for our

camera is now Adobe RGB.

D On a Canon EOS Rebel, we selected the Parameters category, pressed Set to get to the sub-menu, then chose Adobe RGB from the submenu.

CANON EOS REBEL

Calibrating your display

Display types

There are two main types of computer displays: a

CRT (cathode ray tube, as in a traditional TV set)

and the more common LCD (liquid crystal display,

or flat panel display) The display performance of

a CRT fluctuates due to its analog technology and

the fact that its display phosphors (which produce

the glowing dots that you see onscreen) fade over

time A CRT display can be calibrated reliably for

only around three years

LCD displays use a grid of fixed-sized liquid

crystals that filter color coming from a back light

source Although you can adjust only the

bright-ness on an LCD (not the contrast), the LCD digital

technology offers more reliable color consistency

than a CRT, without the characteristic flickering of

a CRT The newest LCD models provide good

view-ing angles, display accurate color, use the desired

daylight temperature of 6500K for the white point

(see below), and are produced under tighter

manu-facturing standards than CRTs Moreover, the color

profile that’s provided with an LCD display (and

that is installed in your system automatically)

usu-ally describes the display characteristics accurately

➤ Both types of displays lose calibration

gradu-ally, and you may not notice the change until

the colors are way off To maintain the color

consistency of your display, stick to a regular

monthly calibration schedule Thankfully, our

calibration software reminds us to recalibrate

our display via a monthly onscreen alert

Understanding the calibration settings

Three basic characteristics are adjusted when a

display is calibrated: The brightness (white level) is

set to a consistent working standard; the contrast

(dark level) is set to the maximum value; and

a neutral gray (gray level) is established using equal

values of R, G, and B To adjust these

characteris-tics, calibration devices evaluate the white point,

black point, and gamma in the display

➤ The white point data enables the display

to project a pure white, which matches

an industry-standard color temperature

Photographers favor using D65/6500K as the

temperature setting for the white point

➤ The black point is the darkest black a display

can project All other dark shades are lighter

than this darkest black, which ensures that shadow details display properly

➤ The gamma defines how midtones are

dis-played onscreen A gamma setting of 1.0 repro-duces the linear brightness scale that is found

in nature Human vision, however, responds

to brightness in a nonlinear fashion, so this setting makes the screen look washed out A higher gamma setting redistributes more of the midtones into the dark range, which our eyes are more sensitive to, and produces a more natural-looking image Photography experts recommend using a gamma setting of 2.2 for both Windows and Macintosh displays

Buying a calibration device

The only way to calibrate a display properly is by using a hardware calibration device, which pro-duces a profile containing the proper white point, black point, and gamma settings for your display

The Adobe color management system, in turn, will use that profile to display colors in your Photoshop document more accurately

If you’re shopping for a calibration device, you’ll notice a wide range in cost, from a $100 to

$300 colorimeter to a much more costly, but more precise, high-end professional gadget, such as a spectrophotometer A colorimeter and its step-by-step wizard tutorial will enable you to calibrate your display more precisely than you could by using subjective “eyeball” judgments

Among moderately priced calibrators, our informal reading of hardware reviews and other industry publications has yielded the follow-ing as some of the current favorites: Spyder3Pro and Spyder3Elite by Datacolor; i1 Display 2 and i1 Display LT by X-Rite; and hueyPro, which was developed jointly by PANTONE and X-Rite

Note: If, after calibrating your display, you intentionally or unintentionally adjust the display’s brightness and contrast settings or change the room lighting (or repaint your walls!), remember

to recalibrate it!

For Mac OS users who don’t have a calibration device, your system supplies a display calibra-tion utility; look for it in System Preferences >

Displays > Color Click Calibrate and follow the instructions that appear onscreen

The steps outlined here apply loosely to the three

hardware display calibrators that are mentioned on

the preceding page We happen to use Spyder3Pro

To calibrate your display using a hardware

device:

1 Set the room lighting to the level that you

nor-mally use for work If you have a CRT, let it warm

up for 30 minutes for the display to stabilize

2. Increase the brightness of your display to its

highest level In the Mac OS, if you have an Apple

display, choose System Preferences > Displays

and drag the Brightness slider to the far right

For a third-party display or any Windows display,

use either a mechanical button on the display or a

menu command in the OnScreen Display (OSD)

3 Launch the calibration application that you’ve

installed, then follow the straightforward

instruc-tions on the step-by-step wizard screens.A–B

You will need to tell the application the

follow-ing important information: your display type

(CRT or LCD), the white point to be used (choose

D65/6500K), and the desired gamma value

(choose 2.2 for both Windows and Macintosh)

For a CRT display, you may see a few more instructional screens requesting further display setting choices

next page), you’ll be prompted to drape the col-orimeter (hardware calibration sensor) over the monitor (B, next page) For an LCD, if a baffle

is included with the calibration device, clip it on

to prevent the suction cups from touching and potentially damaging the screen Follow the instructions to align the sensor with the image onscreen Click OK or Continue to initiate the series of calibration tests, which will take from

5 to 8 minutes

5 After removing the calibration sensor, you’ll

be prompted to name your new display profile (C, next page) Include the date in the profile name, for your own reference The application will place the new profile in the correct loca-tion for your Windows or Macintosh operating system The wizard will step you through one

or two more screens, and then you’re done

When launched, Photoshop will automatically

be aware of the new display profile

A After launching the Sypder3Pro applica-tion, we answered questions on the Display Type screens to tell the wizard software what type of monitor we have and what features it has We clicked Next to progress from screen to screen

B On this Methods of Attachment screen, we clicked No Suction Cup

A The resulting settings appeared

on this Current Settings screen Click

Continue with These Settings

Note: If you have already used the

device to calibrate your monitor, a

screen entitled CheckCAL will appear

instead of this one Click CheckCAL –

Check Current Calibration.

B When this Measuring Display screen

appeared, we draped the colorimeter

over the monitor and aligned it with the

onscreen image, then clicked Continue

to initiate the actual calibration process.

C When the calibration was finished,

we clicked Next, and this Specify Profile

Name screen appeared In our profile

name, we included the monitor name

and the current date.

After we clicked Next again, the

SpyderProof screen appeared We

clicked Switch to compare the pre- and

postcalibration results Finally, we

clicked Next, chose Quit, then clicked

Next one last time to exit the software.