Desktop PublishingCarnegie-Mellon University

Spring 2001

• Dave WattersonArt Director, GATF

• wttrsn@aol.com

• dwatterson@gatf.org

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

1. The basic colors that are used in color process

printing are __________ _________ __________

__________

2. Your monitor uses the _____________ color model

3. The combination of red, green and blue colors on screen can produce more

than _____________ million colors.

4. The file size of a 72 dpi file that is increased to 144 dpi will be ________

times the size of the original.

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.

6. In QuarkXPress the tool needed to edit elements within a selected text or

picture box is the __________ tool.

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 pixel’s 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

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 image’s mode

• Scanned images have three channels– Red, Green and Blue

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

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 IX

Flatbed Scanner

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

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!

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

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

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

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.

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...

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

Today’s 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 workstation’s monitor

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

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 monitor’s current profile

Embedding the Profile• Your chosen color space’s 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

Watch Out for

Save a Copy !

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

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

Defining the Color Space Definitions

• Apple RGB — This color space reflects the gamut of an Apple 13” color monitor

– It’s 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

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

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– It’s based on a proposed new HDTV color

standard• This is a good

prepress space, with a wider gamut than ColorMatch

Defining the Color Space Definitions

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

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!

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!

Defining a CMYK Color Space

• We can also define CMYK data values with an ICC Profile, based upon a specific output device’s reproduction characteristics

• This profile is useful when applications make a CMYK-to-CMYK conversion

Getting Ready to Work

• Before you start doing production work, make sure you’re happy with two things:

A: Your monitor’s calibration

B: Your choice of RGB working space

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

Setting the Monitor Profile• If it’s not listed, check with your monitor

manufacturer to see if a generic ICC profile is available

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, you’ll need to measure your monitor’s color output as a series of colored squares are generated

X-Rite DTP-92Monitor Optimizer

Calibrating Your Monitor Cheaply

• If you don’t have a monitor calibrator, try Photoshop’s Adobe Gamma application– inside Goodies>Calibration

• This is a visual calibration tool that results in a custom ICC profile for your monitor

B: RGB Setup• Select an appropriate RGB working space by

selecting File>Color Settings>RGB Setup• Turn on the

Preview box as well as the Display Using Monitor Compensation box

For Prepress, Adobe Recommends:

Photoshop 5 Workflow Issues

• Now that color space definitions can be embedded into your images, you’ll 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

Three Workflow Scenarios

Photoshop’s working

color space

Legacy files(no embedded color space)

Supplied files with embedded color spaces that don’t

match yours

New scans

1 2 3

Scenario 1: New Scans• Since you’ve 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

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 file’s origin

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

Contacting me

• I don’t 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

Thanks for your attention!

Now let’s head over to the lab

(CFA Room 318)