Desktop Publishing CarnegieMellon University Spring 2001

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Desktop PublishingCarnegie-Mellon
UniversitySpring 2001

• Dave WattersonArt Director, GATF
• wttrsn_at_aol.com
• dwatterson_at_gatf.org

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Welcome to Desktop Jeopardy!

• 3 teams
• 2 questions to each team
• Each question worth 10 points
• If that team misses you have the opportunity to
  steal

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1. The basic colors that are used in color
process printing are __________ _________
__________ __________
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2. Your monitor uses the _____________ color
model
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3. The combination of red, green and blue colors
on screen can produce more than _____________
million colors.
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4. The file size of a 72 dpi file that is
increased to 144 dpi will be ________times the
size of the original.
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5. For printed material to display natural
looking halftones it is recommended that the
image dpi is ______ times the line screen used
in the printing method.
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6. In QuarkXPress the tool needed to edit
elements within a selected text or picture box
is the __________ tool.
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Keeping Pixels in Color Channels

• A definition of pixel might be
• The smallest tonal element in digital imaging
  that can be independently assigned color and
  intensity
• Think of each pixels value as maximum density,
  maximum brightness or a shade in between
• By combining various shades of primary color
  pixels, we can make millions of colors
• Photoshop stores these primary colors in channels

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Color Channels

• Color images have multiple color channels
• (such as the red, green and blue channels of a
  projection TV system)
• The channels used depend on the images mode
• Scanned images have three channels
• Red, Green and Blue

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Workflows RGB versus CMYK

• In the past, most images were converted to CMYK
  as quickly as possible in the workflow
• This conversion normally occurred on the
  high-end drum scanner
• Additional color correction would also occur in
  the CMYK mode

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Workflows RGB versus CMYK

• Today, scanners are most often used to capture
  RGB or LAB data for later conversion to CMYK
• This provides greater flexibility in how the
  scan can be used
• This is also a key component of a color
  management workflow

Heidelberg Topaz IXFlatbed Scanner
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Advantages of the CMYK Mode

• The only widely-used method for creating a
  printable image
• Alternative, hi-fi color reproduction methods
  are possible
• CMYK images can be easily proofed with
  photomechanical or digital methods

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Disadvantages of the CMYK mode

• Color is less intense than RGB
• Available gamut (range of colors) is smaller than
  RGB
• CMYK is not the mode required for viewing images
  on a monitor
• Your CMYK image will be converted to RGB so that
  you can view it on your monitor!

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Repurposing CMYK Images

• Reusing CMYK images on a different output device
  may require adjusting the image's
• highlight, midrange, and shadow dot
• overall gray balance
• color saturation
• Changing the image's black plate can harm image
  quality, but printing the image without modifying
  the black plate can create an unacceptable result

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The Benefits of RGB

• Wider color gamut provides a more accurate
  recreation of the original
• Native color mode for computer monitors
• An RGB file takes up only 75 of the disk space
  needed for a CMYK file
• Color corrections on RGB images are easier and
  cause less harm to the image
• Allows the same image to be color separated over
  and over for different output devices

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Correct First, Separate Later

• If a color cast can be identified in an RGB
  image, the adjustments required are simple and
  affect the image's entire tonal range in a
  balanced manner
• However, if you wait until the image has been
  separated to perform the same color correction,
  the effect of the color cast has been distributed
  among all four channels
• The effects of this cast may be impossible to
  remove

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Color Mode versus Color Space

• Color mode the choice of several broadly
  accepted methods for storing color data in
  individual channels
• RGB, CMYK, CIELAB, Indexed Color, etc.
• Color space a specific set of data used to
  characterize pixel values within a color mode
• Defines how red is red? by associating RGB
  values from 0 to 255 with specific
  spectrophotometric values
• sRGB, Apple RGB, ColorMatch RGB, etc.

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Why Do We Need Color Spaces?

• In order to perform any sort of editing upon a
  digital file, the image editing application has
  to know how the values of each pixel relate to
  the total number of colors available
• This provides a method of defining pixel colors
  into a device independent set of values
• Photoshop has always brought RGB pixels into a
  known working space when an image is opened...

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History of Photoshop Color Spaces

• Photoshop 3 and older used a hard-wired color
  space definition known as Apple RGB, which
  reflected the values produced by an Apple 13
  color monitor
• Photoshop 4 also used this color space, unless
  your Mac was running ColorSync in this case,
  the monitor profile specified in the ColorSync
  Control Panel became your RGB working space in
  Photoshop

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Todays Photoshop Color Spaces

• Photoshop 5 has unlinked the ColorSync system
  profile from the working space
• The selection made in the ColorSync Control Panel
  now only corrects RGB data for your monitor
• This allows the RGB values of the working space
  to be portable between computers, regardless of
  the characteristics of each workstations monitor

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RGB Color Space ICC Profile

• The information about your chosen RGB color space
  definition is saved in a format defined by the
  International Color Consortium (ICC)
• Definitions in this format are called ICC
  Profiles

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Choosing a Color Space

• Within Photoshop, selecting RGB Setup will allow
  you to select an RGB working space from a list of
  9 pre-defined options
• You can also define a custom RGB space, or choose
  your monitors current profile

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Embedding the Profile

• Your chosen color spaces definition can be
  embedded within your image, so that any other
  applications which may process this image are
  aware of how these colors should be
  represented
• This is essential for a color managed workflow

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Watch Out for Save a Copy !

• If youre in the habit of choosing Save a Copy,
  be aware that selecting Exclude Non-image Data
  will save your file without embedding a profile!

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Defining the Color Space Definitions

• sRGB This color space was created by
  Hewlett-Packard, and mirrors the gamut of a
  low-cost home PC monitor
• sRGB also complies to the specs for HDTV

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Defining the Color Space Definitions

• Apple RGB This color space reflects the gamut
  of an Apple 13 color monitor
• Its the color space used by Photoshop 3 (as well
  as Photoshop 4 when ColorSync was disabled)
• This space is not much better than sRGB,
  although the definitions are different

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Defining the Color Space Definitions

• ColorMatch RGB This space is based on the
  Radius PressView monitor, and is a good choice
  for prepress applications
• The D50 white point matches that used in ANSI
  viewing booths

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Defining the Color Space Definitions

• Adobe RGB (1998) Formerly known as the
  SMPTE-240M color space, this was renamed after
  SMPTE did not approve these specs
• Its based on a proposed new HDTV color standard
• This is a good prepress space, with a wider
  gamut than ColorMatch

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Defining the Color Space Definitions

• PAL/SECAM This matches the specs for European
  broadcast video, and is not a good choice for
  prepress applications

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Defining the Color Space Definitions

• SMPTE-C This matches the specs for American
  broadcast video, and is not a good choice for
  prepress applications either!

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Defining the Color Space Definitions

• Wide Gamut RGB This color space was created by
  defining spectrally pure primary colors, and can
  include many colors that are beyond the
  capabilities of both monitors and output devices
• This space should only be used with great
  caution and testing!

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Defining a CMYK Color Space

• We can also define CMYK data values with an ICC
  Profile, based upon a specific output devices
  reproduction characteristics
• This profile is useful when applications make a
  CMYK-to-CMYK conversion

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Getting Ready to Work

• Before you start doing production work, make sure
  youre happy with two things
• A Your monitors calibration
• B Your choice of RGB working space

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A Monitor RGB

• The ColorSync System Profile Control Panel
  contained in the Mac OS controls the conversion
  of RGB scan data into the RGB PICT data for
  your monitor
• You may be able to find your monitor in the
  preinstalled list of monitors supplied by Apple,
  or you might generate your own custom ICC monitor
  profile

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Setting the Monitor Profile

• If its not listed, check with your monitor
  manufacturer to see if a generic ICC profile is
  available

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Making an ICC Monitor Profile

• Of course, the most accurate ICC monitor profile
  is one that is individually created for your
  monitor
• To create such a profile, youll need to measure
  your monitors color output as a series of
  colored squares are generated

X-Rite DTP-92 Monitor Optimizer
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Calibrating Your Monitor Cheaply

• If you dont have a monitor calibrator, try
  Photoshops Adobe Gamma application
• inside GoodiesCalibration
• This is a visual calibration tool that results
  in a custom ICC profile for your monitor

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B RGB Setup

• Select an appropriate RGB working space by
  selecting FileColor SettingsRGB Setup
• Turn on the Preview box as well as the Display
  Using Monitor Compensation box

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For Prepress, Adobe Recommends
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Photoshop 5 Workflow Issues

• Now that color space definitions can be embedded
  into your images, youll have some decisions to
  make about how files should be handled upon
  opening
• Most of your legacy files (created prior to
  Photoshop 5) will have no embedded profiles
• In addition, customers will supply files with
  embedded profiles that are different from your
  chosen color space

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Three Workflow Scenarios
1
2
3

• Supplied files with embedded color spaces that
  dont match yours

• Legacy files(no embedded color space)

• New scans

• Photoshops working color space

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Scenario 1 New Scans

• Since youve already calibrated your monitor and
  selected an RGB working space, this one is easy!
  Simply open your RGB scans and make any needed
  adjustments
• Make certain that your Profile Setup is checked
  to embed RGB and CMYK profiles

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Scenario 2 Legacy Scans

• Set your Assumed Profile to Ask When Opening so
  you can make the appropriate choice every time
  you convert a file to your preferred RGB color
  space
• The From color space should match the files
  origin

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Scenario 3 Profile Mismatch

• Set your Profile Mismatch Handling to Ask When
  Opening so you can make the appropriate choice
  every time you convert a file to your RGB
  working space

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Contacting me

• I dont have an office on campus and really work
  all day
• Please e-mail me and I will set up a meeting time
  as quickly as possible

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Thanks for your attention! Now lets head over
to the lab(CFA Room 318)