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Color Management for Production PrintingConnectivity Master Full Training Module

Created by: Group L&D Version:1.1.a Classification: Ricoh Family Group Internal use only

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Objectives

After completing this training you should be able to explain: the basics of color management. some of the terminology used in production color printing.

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Requirements

PC running Windows.

This presentation.

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Pre-requisites and exam

There are no pre-requisites.

At the end of this course, you can do the exam on WICE.

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Module Overview

1. Introduction

2. What is Color

3. Describing Color

4. Color Management

5. Color Management Systems

6. Proofing

7. Profiling

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1. Introduction

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Introduction to Color Management

Color is important to businesses based on their specific needs. For instance, many organizations have a corporate or brand

color that is a key element of their brand identities. These colors must be accurately reproduced, regardless of

whether or not the branded items are printed using offset or digital printing or other technologies.

However, to achieve this accurate reproduction, people have to rely on color management, which has always been regarded as something difficult and only for color geeks.

This presentation will show you the fundamentals of color and color management in, hopefully, an easy way. It will define color terms and it will explain the tools and

processes behind color reproduction.

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2. What is Color

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Color Basics

Color is the visual sensation produced in response to selective absorption of wavelengths from visible light.

To see an object it must either emit light, as the sun does, or reflect it from another source, such as the moon reflecting sunlight.

Color is generally described using additive or subtractive models.

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Light

So what exactly is light? Light is actually a form of electromagnetic radiation. What is electromagnetic radiation, then? Electromagnetic radiation has a dual nature as both

particles and waves, as explained on the next slides.

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Electromagnetic Wave

The traditional way is to describe light as being an electromagnetic wave.

This wave has amplitude, which is the brightness of the light, wavelength, which is the color of the light, and an angle at which it is vibrating, called polarization.

The wave theory of light was happily adopted and accepted until it was found to fail to explain some observed and measured phenomena.

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Quantum Theory

In terms of the modern quantum theory, electromagnetic radiation consists of particles called photons.

Photons are packets ("quanta") of energy which move at the speed of light. In this particle view of light, the brightness of the light is the

number of photons, the color of the light is the energy contained in each photon, and four numbers (X, Y, Z and T) are the polarization.

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Electromagnetic Spectrum

Both interpretations are correct, but the wave viewpoint is primarily used, since it is a more useful description.

The human color perception range is between ultraviolet (400nm) and infrared (700nm).

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White Light

Sir Isaac Newton was the first to realize that white light actually contains all colors.

A nice tool to show that is the prism.

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RGB

Light with a wavelength between 600 and 700 nm is known as red light.

Light with a wavelength between 500 and 600 nm is known as green light.

Light with a wavelength between 400 and 500 nm is known as blue light.

400 500 600 700Blue Green Red

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Seeing Color

When we see light, there are 3 important elements that influence color perception: The light source. The colored object. The eye.

Light source

Colored object

Light sensor

(human eye)

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Eye Mechanism

Eyes have a structure similar to cameras.

Two types of light-sensitive cells in the retina: rods and cones.

There are three types of cone cells, each sensitive to a specific range of wavelengths (red, green and blue).

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Perceiving Colors

We can see: reflected light

(intrinsic color). transmitted light

(luminous color) Color is perceived by the

reflection of light off an object.

The way a color looks is relative to the viewer.

Transmitted Light

Reflected Light

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Color Perception (1/2)

The light source emits light. This is known as luminous

color. The object absorbs colors

and reflects colors. The human eye perceives

color based on the objects that light is reflected from. This light is known as

intrinsic color.

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Color Perception (2/2)

Perception of colors depends on: The light-source. The observer. the surrounding colors.

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The light source

The color of a light source is described by its temperature. Color temperatures are measured using the Kelvin scale.

Warmer temperatures emit bluish light. Cooler temperatures emit reds.

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Metamerism

Metamerism is an illusion in which two or more colors appear identical under certain light sources, but are different from each other under other lights or to a different observer.

This is a common problem in the color printing business. That is the reason why many professionals use a light

cabinet to evaluate their prints.

Light cabinetmetamerism.exe

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Fluorescence

Some atoms and molecules have the ability to absorb photons of a certain energy level, and emit photons of a lower energy level.

This is called fluorescence, and can sometimes change one type of visible (or even invisible ultraviolet) wavelength into another visible wavelength.

Many paper manufacturers add fluorescent brighteners (optical brighteners or bluing agents) to whiten the slightly yellowish paper.

Paper with optical brighteners, seen using a black light

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Additive Colors (RGB)

By combining Red, Green and Blue light we can create all the colors of the visible light-spectrum.

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RGB Color Monitors

CRT LCD

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Subtractive Colors (CMY)

Using Cyan, Yellow and Magenta toners we can create colors on paper.

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Complementary Colors

In the color theory, two colors are called complementary if, when mixed in the proper proportion, they produce a neutral color (grey, white, or black). Red is the complement color of cyan. Green is the complement color of magenta. Blue is the complement color of yellow.

R G B

C M Y

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White Paper Reflection

In theory, white paper reflects all colors. This is a theoretical statement, because different brands

of paper have a different color. This is why in color management it is very important to

know what paper we are using. This is not only true for the output, but also for the original.

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Yellow Toner Absorbs Blue Light

Yellow is the complement of blue. Yellow toner absorbs blue light and reflects green and red

light. The reflected “G” and “R” light are seen as yellow.

R

G B

Y

C M

R

G

B

C

M

Y

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Magenta Toner Absorbs Green Light

Magenta is the complement of green. Magenta toner absorbs green light and reflects blue and

red light. The reflected “B” and “R” light are seen as magenta.

R

G B

Y

C M

R

G

B

C

M

Y

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Cyan Toner Absorbs Red Light

Cyan is the complement of red. Cyan toner absorbs red light and reflects green and blue

light. The reflected “B” and “G” light are seen as cyan.

R

G B

Y

C M

R

G

B

C

M

Y

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Mixing Subtractive Colors

Equal amounts of magenta and yellow toner produces red. Equal amounts of cyan and yellow toner produces green. Equal amounts of magenta and cyan toner produces blue.

Y

C M

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Process Black

In theory, equal amounts of C, M and Y produce black. This black is called “Process Black”. In reality, it is virtually impossible to produce true black

using cyan, magenta and yellow toner. Depending on the used toners or inks, the result can vary

form deep blue to be brown or gray.

Pure black Process black

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Under Color Removal (UCR)

One way of reducing the “Process Black” problem is UCR or Under Color Removal.

UCR replaces an equal amount of yellow, cyan and magenta with black toner, but only in dark, near neutral colors.

Advantages: Lower toner consumption. Better reproduction of black.

Disadvantage: The image lacks depth if high UCR ratios are used like in

Letter Mode. That is the reason why 100% UCR is not used very often.

60% UCR

100% UCR

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Gray Component Removal (GCR)

GCR has the same function as UCR. The difference between GCR and UCR is that GCR starts

at lower image densities. It can be used for neutral and non-neutral colors that are

either light or dark

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UCR vs GCR

The pictures show the difference between UCR and GCR.

You can clearly see that GCR starts earlier with color replacement.

UCR

GCR

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3. Describing Color

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Chapter Overview

1. Introduction to Describing Color

2. Color Wheels

3. HSB/ HSL

4. Named Colors

5. Spot Colors

6. CIE Color Model

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3.1 Introduction to Describing Color

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Describing Color

Color is often difficult to communicate about. The reason is that the words we use to describe color are

vague and frequently misunderstood. Not only are technical terms such as "value," "saturation"

and "chromaticity" confusing but even simple words such as "bright," "pure," "shiny" and "dim" are hard to use accurately.

Even the experts struggle without a set of standardized definitions.

We need numerical models to manipulate and predict colors, simply because we use computers.

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Color Models

Both scientists and artists have long struggled to come up with a model that would be able to describe al colors.

Famous people like Newton, Goethe and Maxwell have tried.

Some modern models are based on the Munsell Color System, developed by Albert H. Munsell.

His model uses different values of hue, brightness (value), and saturation (chroma) to define colors more accurately.

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Color Terminology – Hue

Hue is the property of color that we are actually asking about.

For example, when we talk about colors that are red, yellow, green, and blue, we are talking about hue.

Different hues are caused by different wavelengths of light.

Therefore, this aspect of color is usually easy to recognize.

Hue Contrast – different hues

Hue Constant – different colors, same hue

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Color Terminology – Chromaticity

Chromaticity describes the purity of a color. That means there is no white, black, or gray present in a

color that has high chroma. These colors will appear vivid and pure. Chromaticity is related to and often confused with

saturation.

High chroma – very shiny and vivid

Low chroma – achromatic, no hue

Constant chroma – medium chroma, similar vividness, less purity than top image

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Color Terminology – Saturation

Related to chromaticity, saturation tells us how a color looks under certain lighting conditions.

For instance, a room painted a solid color will appear different at night than in daylight.

Over the course of the day, although the color is the same, the saturation changes.

This property of color can also be called intensity.

Saturation constant – same intensity, different hue

Saturation contrast – various levels of fullness, same hue

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Color Terminology – Value

When we describe a color as "light" or "dark", we are discussing its value or "brightness“, “lightness” or “luminance”.

This property of color tells us how light or dark a color is based on how close it is to white.

Low Value, Constant – same brightness level

Contrast of Value – grayscale = no chroma

Contrast of Value – big differences in brightness

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Brightness or Lightness

In color science, there is a distinction between lightness and brightness, although the 2 words mean the same.

The strict definition of lightness: lightness is the brightness of an object relative to an absolute white reference.

This means that lightness ranges from dark to light, with specific definitions of black and white as the limits. We can measure lightness

and assign specific numerical values to it.

Brightness ranges from dim to bright with no real limits. It is just a subjective

sensation in our heads.HSL and HSB are derived from the Munsell Color System, describing Lightness and Brightness

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3.2 Color Wheels

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Color Wheels

The color wheel or color circle is the basic tool for combining colors.

The first circular color diagram was designed by Sir Isaac Newton in 1660.

The color wheel is designed so that virtually any colors you pick from it will look good together.

Over the years, many variations of the basic design have been made, but the most common version is a wheel of 12 colors based on the RYB (or artistic) color model.

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3.3 HSL and HSB

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HSL and HSB/HSV

Derived from the Munsell Color System are the HSL and HSB models.

They are the two most common cylindrical-coordinate representations of points in an RGB color model. HSL stands for hue, saturation, and lightness, and is often

also called HLS. HSB stands for hue, saturation, and brightness, and is also

often called HSV (V for value). The major difference is in the shape of the 2 models.

HSB uses 1 cone to display all colors, while HSL uses 2 cones.

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HSL

HSL uses 2 cones to display the colors. Used for example in Microsoft Office.

HSL in MS Office

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HSB

HSB uses a single cone. Used for example in Adobe Photoshop.

HSB Sliders in Photoshop

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3.4 Named Colors

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Named Colors

In essence, a named color is a color with a name and an RGB value.

Example: the color crimson, with RGB values 220, 20, 60.

This is used for instance for building websites. A complete list of the color names supported by all major

browsers can be found on the internet. In the printing industry, the use of RGB values is not used

very often, since most printing devices use CMYK toners/ inks. Instead, spot colors are used.

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3.5 Spot Colors

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Spot Colors

In offset printing, a spot color is any color generated by an ink (pure or mixed) that is printed using a single run.

Technically speaking, the 4 colors that the offset uses to print are also spot colors.

However, generally speaking, when we talk about spot colors, we mean a color other then CMYK. More specifically, any color generated by a non-standard

offset ink, such as metallic, fluorescent, spot varnish, or custom hand-mixed inks.

Spot colors are also named colors, because all spot colors have a name.

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Spot Color Library

The spot colors are contained in a library: the spot color library.

There are several industry standards in the classification of spot color systems

To name a few: Pantone

The dominant spot color printing system in the United States and Europe.

Toyo A common spot color system in Japan.

DIC Another common Japanese spot color system.

HKS A German color system.

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Pantone

As said before, Pantone is the dominant spot color system in Europe and the US.

The Pantone Color Matching System (PMS) is a standardized color reproduction system.

Since all Pantone colors are standardized, different manufacturers in different locations can all refer to the Pantone system to make sure colors match.

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Pantone Guide

The Pantone guides are sets of thin cardboard sheets, containing all Pantone colors.

There are several guides, for specific media (coated, uncoated etc.).

In PMS, all Pantone colors have a unique number. For instance, PMS 130 is a yellow tint.

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Problem

The Pantone spot color library was never designed, nor intended, to be used as a way to specify colors that will be printed using CMYK toners or inks.

As a result, because of the gamut differences, CMYK process simulations of the Pantone library can only provide an approximation and in the majority of cases, deliver disappointing results.

SpotCMYK

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Pantone Colors

However, most of the world's printed material is produced using the CMYK process, so there is a special subset of Pantone colors that can be reproduced using CMYK.

These are labeled as such within the company's guides and are called the Pantone Process Colors.

The rest of the Pantone system's colors cannot be accurately simulated with CMYK. Instead, 13 base pigments are used (15 including white and

black) mixed in specified amounts.

Example of the Pantone Process library in Photoshop

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CMYK Equivalents

You will find the Pantone Process Colors, including their CMYK equivalents on the Pantone Guides.

Important to know is that these CMYK values are based on offset inks, and not on CMYK toners or inkjet inks.

The Pantone color may not be accurately reproduced when you print these CMYK values on a Ricoh color laser printer.

Pantone color swatch Pantone color printed

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Built-in Library

Instead of relying on the indicated CMYK values, many printer/ controller manufacturers use their own built-in spot color libraries.

The printer will use the values as indicated by the built-in library instead of printing the spot color with the CMYK equivalents as indicated by the spot color manufacturer.

This ensures a better match, since the built-in library is custom-made for each printer type.

Some Ricoh devices can be connected to a Fiery or Creo printer controller.

These controllers allow operators to fine tune the CMYK values for spot colors, to achieve an even better match.

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3.6 CIE Color Model

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Tristimulus

The term tristimulus refers to experiments and measurements of human color vision involving three color stimuli, which the test subject uses to match a target stimulus.

The most comprehensive model has been defined by the CIE (Commission Internationale de l’Eclairage) back in 1931.

In fact, it is so comprehensive that it forms the basis for color management as we know it.

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The CIE Color Model

The CIE color model is device-independent, which allows us to describe color in such a way that it can be reproduced consistently and accurately on different equipment.

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CIE Chromaticity Diagram (CIE XYZ)

This diagram represents the colors of the spectrum.

All colors that can be recognized by the human visual system are within these curves.

A vertical axis (Y) represents brightness, to include browns, grays, etc.

Important to know is that CIE XYZ does not factor in the non-linearity of the human eye, so the distances are distorted.

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The CIE LAB Model

CIE LAB is the second of 2 systems adopted by the CIE.

It is an attempt to reduce the distortion in color distances.

LAB is based on XYZ, but is non-linear, to try to mimic the human senses. L is a luminance scale. a and b are color axes.

Although not perfect, it is the most useful system today. There are many other

models like CIE LCh, CIELUV, CIE xyZ, etc. but they are not commonly used.

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Delta E (∆E), Delta H (∆H), Delta T (∆T)

The CIE Color Model also allows for computations of color difference.

These differences can be measured as delta E, delta T or delta H.

This can be important, since it allows users to actually measure any differences in color, rather then relying on visual inspection. Think of comparison between output of a digital printer and

an offset press, between actual print and target or between pages in a single job.

∆E, ∆H and ∆T in EFI Color Profiler Suite

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Color Bar or Job Slug

To measure the difference in color, you can print a control bar alongside the actual print job.

Color Verifier of EFI Color Profiler Suite

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Delta E (∆E)

Delta E (Euclidian distance) is defined as the difference between two colors in an L*a*b* color space.

The following delta E values are valid universally: 0 - 1: A normally invisible difference. 1 - 2: Very small difference, only obvious to a trained eye. 2 - 3: Medium difference, also obvious to an untrained eye. 3,5 - 5: An obvious difference. > 6: A very obvious difference.

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Delta H (∆H)

The absolute color difference between two samples is known as the hue difference (delta h*).

This measured value is used to calculate the fractional value of delta E, which evolves from the hue difference between two color samples alone.

Differences in brightness are ignored during the calculation of delta H.

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Delta T (∆T)

Delta T describes the colorimetrically calculated dot gain defined by ISO 12647-7.

Delta T stands for the tone differences between the reference and the result.

These tolerances can only be measured for the primary colors, e.g. 100% cyan.

It is not possible to calculate delta T values for colors composed of a mixture of cyan, magenta, yellow and black.

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LAB Limitations

Although the CIE LAB model is pretty good, it does have some limitations.

For one, it is not as uniform as it was supposed to be. Changing one of the primary colors by a certain increment

does not always produce the same degree of visual change. Another limitation is that CIE LAB assumes that a straight

hue-angle line will produce constant hues, changing only in saturation, but unfortunately that is not the case.

Hue shift from purple to blue

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PowerPoint Blue

Ever had problems with printing for instance PowerPoint slides with a blue background?

Since the blue of the background is so highly saturated, most printers cannot print it.

Instead, following a straight line to pure white, the first color that is within the printer’s gamut will be used. Since this is a very common problem, many print

manufacturers have a built-in compensation for this phenomena.

Highly saturated blue, impossible to print

Printer gamut

Instead of blue, purple will be printed

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4. Color Management

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Color Management (1/2)

In digital imaging systems, color management is the controlled conversion between the color representations of various devices, such as digital cameras, scanners and printing devices.

The primary goal of color management is to obtain a good match across color devices.

For example, colors from a photograph, taken with a digital camera, should look pretty similar on a monitor and on the printed output.

In other words: WYSIWYG or What You See Is What You Get.

Note that true WYSIWYG will not be possible. However, with proper color management, you can produce

a close and consistent output, which, with little learning, allows you to predict the final output.

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Color Management (2/2)

Another important goal of color management is to make it usable.

In the “old days”, color management was not needed, because all images were scanned by professional operators, on a single scanner which produced CMYK output, optimized for a particular printer.

This system worked because it was a closed loop that dealt with only one scanner and one printer.

But today, we have thousands of different input and output devices which have to be connected.

And worse, they still need to produce predictable results and need to provide WYSIWYG, one way or the other.

Color management deals with this in a smart way, as you can see in the next slide.

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With or Without Color Management

Old style “Color Management”.

Color Management with device independent color space (PCS).

PCS

N input M output

N x M conversions

N + M conversions

N input M output

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ICC

The most popular color management systems make use of the ICC (International Color Consortium) workflow.

It makes use of 4 basic components: PCS. Profiles. CMM. Rendering intents.

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Monitor Profile

Output profile

Reference Color Space

Input Profile

CIE Lab

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PCS

The PCS or Profile Connection Space allows us to give a color an unambiguous numerical value in CIE XYZ or CIE LAB.

It is a device independent color space which defines color as we actually see it.

The PCS is used as the “hub” through which all color conversions travel.

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Profiles

Profiles describe the relationship between a device’s RGB or CMYK control signals and the actual color it produces.

In other words, it defines the CIELAB values that corresponds to a given set of CMYK or RGB numbers.

Profiles can describe: A single device, such as an

individual scanner, monitor or printer.

A class of devices, such as Apple Cinema Displays, Euroscale presses etc.

An abstract color space, such as Adobe RGB (1998) or sRGB.

But whatever it describes, in essence it is just a look-up table.

Video Gamut RGB

Adobe RGB (1998)

sRGB

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CMM

The CMM or Color Management Module is the engine of color management.

It is a piece of software that performs all the calculations needed to convert the RGB or CMYK values.

It works with the color data contained in the profiles. Note that although there are several CMMs, for instance

from Adobe, Agfa, Heidelberg, Kodak, EFI, which are designed to be interoperable and interchangeable, they do tend to vary, especially when profiles are tailor-made for a particular CMM. This means that you can get different results from using

different CMMs.

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Rendering intents

The ICC specification includes 4 rendering intents. These are, simply put, different ways of handling “out of

gamut” colors, so colors which cannot be reproduced by an output device.

The 4 intents are: Presentation or Saturation. Photographic or Perceptual. Relative Colorimetric. Absolute Colorimetric.

Example of rendering intents on a Fiery controller

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Gamut?

In digital printing, when we talk about “gamut” we mean the color space of a device.

Devices can be divided into 2 categories: RGB devices like scanners, monitors, digital cameras etc. CMYK devices like laser printers, offset etc.

Normally, in general, a CMYK printer device color space will be smaller (less saturated and fewer colors) than a RGB capture device color space.

A typical RGB color space

A typical CMYK color space

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Gamut Mapping

When printing, a source gamut has to be translated into a destination gamut.

For instance, when printing a photograph, taken with a digital camera, the gamut of the camera has to be translated into the gamut of the printer. Some colors from the camera may be outside of the gamut

of the printer, so these colors need to be shifted inside the gamut of the printer.

This process is called “gamut mapping”, and is done through color management.

As explained before, 4 rendering intents can be chosen to do the gamut mapping, so let us have a look at what they actually do.

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Presentation

Also called Saturation Rendering. It maps the saturated primary colors in the source space

to the saturated primary colors in the target space, without bothering about differences in hue, saturation or lightness.

It is designed for rendering business graphics like pie and bar charts, where we simply want vivid colors and are not particularly concerned as to exactly what those colors are.

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Photographic

Also called Perceptual Rendering. It attempts to compress the gamut of the source space

into the gamut of the target space. It de-saturates all colors to bring the out-of-gamut colors

into the target gamut while more or less maintaining the overall relationship between colors.

Preserving the relationship between colors helps preserve the overall appearance of images.

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Absolute Colorimetric

Also called Match Intent. Reproduces in-gamut colors exactly, and clips out-of-

gamut colors into the closest color at the gamut boundary. Problems with Abs Colorimetric:

White in the image appears to have a color cast. Because the relationship between in- en out-of-gamut colors

is changes, often the image is destroyed.

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Relative Colorimetric

Also called Proof Intent. Similar to Absolute Colorimetric Rendering. The only difference is that Relative Colorimetric scales the

white point of the source to the white point of the target. Brightness may be modified so that all the brightness

levels are within the range of brightness of the destination gamut in use.

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Profiles and CMM

Most color-managed applications let you assign profiles to images and other colored objects.

For example, Photoshop allows you to assign a profile to an image.

When these images are then used in applications like Adobe Illustrator or InDesign, the CMM will use the embedded profiles for correct color management. Although this is done automatically, most CMMs do allow

you to override these embedded profiles when needed.

Example on a Fiery controller: use embedded profile or select one yourself

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Shortcomings

Besides all the positive points there are a few negative things about the ICC workflow as well.

The “intelligence” of the ICC workflow lies in the profiles, rather then in the Color Management Module used to connect the source and output profiles.

This can result in inaccuracies or unnecessary desaturation in color conversions.

In some cases, 2 otherwise perfectly fine profiles just seem to cause problems when you use them together.

The next slides will show some other examples of unwanted results.

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Black Channel

When converting the source profile into Lab, and from Lab to output profile, the black channel information is lost.

The reason is that Lab is only 3 dimensional, while CMYK is 4 dimensional.

For some users, this is not acceptable.

The work around for this problem is the device link.

Lab

C 60%

M 23%

Y 0%

K 100%

C 12%

M 12%

Y 2%

K 70%

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Device Link

A device link will directly connect a source profile to an output profile, without conversion to or from Lab.

The result will be a much more accurate conversion. It allows preservation for black channel, as well as for pure

primaries. For Fiery controllers, device links can be created with

specialized software (EFI Color Profiler Suite, Gretag MacBeth Profile Maker etc).

Other controllers (Creo controllers, for instance) create device links on the fly, when selecting a source and output profile.

Lab

C 60%

M 23%

Y 0%

K 100%

C 20%

M 16%

Y 1%

K 100%

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Gamut Mapping

Another example of the ICC workflow flaw is that gamut mapping is not intelligent.

Lets assume you want to print a photograph, taken with a digital camera. Source profile camera: Adobe 1998. Output profile: device profile printer.

Lets again assume that all the colors that the camera has shot are all well within the gamut of the printer.

As you print a photograph, it is likely you will choose the photographic rendering intent.

When you press the Print button, without even checking the colors of the photograph, the complete Adobe 1998 gamut will be compressed into the output profile of the printer, thereby unnecessarily changing all colors.

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Workaround

Actually, the only available workaround is to use your brains.

Do not blindly select a rendering intent. For this job, the colorimetric intent was probably a better

choice.

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CMM and Bad Images

One thing to remember is that color management does not take a bad image and make it look good on output.

It does not eliminate the need for color correction. What it does is make sure that the image (and all its

shortcomings) are faithfully reproduced on the output device.

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Color Management and Memory Colors

Memory colors are colors like green grass, blue sky and skin tones.

These colors matter more than others because we have such a strong memory of them.

Even if a print is colorimetrically correct, when for example the skin tones are not what the viewer expects, the image looks wrong.

This is a psychological aspect of human color perception that we cannot put in a model, so color management cannot address this.

This means that sometimes human intervention is needed to correct the output.

Example of a faithfully reproduced image, which does not look right.

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5. Color Management Systems

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Chapter Overview

1. Introduction

2. ColorSync

3. ICM

4. WCS

5. Applications

6. Printer Driver

7. Color Controllers

8. Prepress Solutions

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5.1 Introduction

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Introduction

There are several ways of how to use color management. All major Operating Systems have a color management

system built-in. Some applications have their own color management

system built-in. Some printer driver have support for color management. And last but not least, many color controllers have an

embedded color management system. No matter what system you use, it is important to stick to

using just one. Having different CMMs trying to color manage a single job

will give you unexpected results. So which one do you use?

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What to Use

As with many things in life: it depends. If you want to print some photographs, taken with your

digital camera, on an inkjet printer, connected to your PC or Mac, you can use the color management system of your Operating System or application.

If you have a certain workflow, where PDFs from unknown origins have to be printed on an professional color device, you are probably better of using the color management system of the printer controller.

The next slides will show some highlights of different color management systems.

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5.2 ColorSync

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ColorSync

ColorSync is Apple’s implementation of the ICC specification, providing system-level color management of images, documents and devices.

ColorSync is fully integrated into Mac OS X, ensuring that powerful color management tools can be accessed from every application for consistent color.

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ColorSync Utility

Every device, connected to Mac OS X, is automatically assigned at least one ICC profile.

In some cases, a single device (e.g. printer) may have several ICC profiles available (a profile for different media types for instance).

In those cases, you can use the ColorSync Utility to manually select the correct profile for each job.

The ColorSync Utility also allows you to view, compare and edit ICC profiles.

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Monitor Calibration

While Mac OS X has already assigned a factory profile to your display, calibration of the display based on your environmental conditions is highly recommended.

Mac OS X provides the tools to do this using the Display Calibrator Assistant.

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5.3 ICM

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Image Color Matching

ICM is the built-in color management system of Windows 95/98/2000/XP, originally developed by Heidelberg.

Like ColorSync, it provides an OS-level color management system based on the ICC workflow. Windows 95 and Windows NT4.0 need an application that

supports ICC profiles. Newer Windows versions offer color management support

on OS level. ICM is not as tightly integrated as ColorSync. In many cases, you have to manually assign ICC profiles

(ICM profiles in Windows) to devices.

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ICM Profiles

In case of Ricoh products, the needed ICM profiles can be downloaded from the Ricoh-Support website, or created using a profiling application, such as EFI Color Profiler Suite or Gretag MacBeth Profile Maker.

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Printer ICM Profile

The correct ICM profile can be assigned to a printer driver in the Color Management tab in the driver.

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Monitor Profile

You can assign a monitor profile in the advanced settings of the display properties.

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Monitor Calibration

ICM does not provide a tool for monitor calibration. You will have to rely on 3rd party applications, for instance

the EFI Color Profiler Suite or the Eye-one Display from Gretag MacBeth.

Since these tools provide excellent results, it should not be regarded as a show stopper for ICM.

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5.4 WCS

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WCS

Starting from Windows Vista, Microsoft introduced a new color architecture known as Windows Color System.

WCS supplements the Image Color Management (ICM) system in Windows 2000 and Windows XP.

The primary reason for the Windows color management architecture is to improve the what-you-see-is-what-you-get (WYSIWYG) quality for printing and imaging.

WCS Provides seamless interoperability with ICC profile-based workflows: ICC-only transforms run through improved ICM3 CMM. Mixed ICC & WCS transforms run through WCS CITE.

It is beyond the scope of this presentation to show you all the ins and outs of WCS.

The next slides will show some highlights.

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Color Management Tab

The use of WCS is most noticeable in the Color Management tabs in the drivers.

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Monitor Calibration

WCS has a built-in monitor calibration wizard. Although it provides acceptable results, it is still

recommended to use 3rd party software for calibration.

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Conclusion

WCS looks promising, but it is not matured yet. It is to early to make any predictions, so we just have to

wait and see what happens to WCS. One thing that would have to change is that applications

like Adobe Photoshop have to be “WCS aware”. At the moment, you can use Photoshop with WCS by

selecting “use icm” in Photoshop. However, for displaying images on your monitor, Photoshop

will still rely on its own icm, using ICC profiles.

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5.5 Applications

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Color Management in Applications (1/2)

Some applications like Photoshop, InDesign, Illustrator, QuarkXPress, have a built-in color management module.

These applications know what ICC profiles are and how to use them, at least to some degree.

The Adobe applications use ACE or Adobe Color Engine. The major benefit of having a built-in proprietary CMM

such as ACE is cross platform operability. No matter if you use these applications on a Mac or on a

Windows platform, ACE produces the same results. Note that many of these built-in CMMs still use ICM or

ColorSync to request the current display profile or to find profiles on the system.

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Color Management in Applications (2/2)

Although the application may be color managed, the actual color management may still be performed by the operating system through ColorSync or ICM.

Other application vendors insist on implementing color management in their own way, using their own interfaces and terminology, making it hard for users to fully understand what the application is doing.

Luckily, Adobe is one of the vendors who is trying to make color management easier for users, by integrating the same CMM in the applications of the Adobe Creative Suite.

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5.6 Printer Driver

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Printer Drivers

When printing to a Ricoh color device, you have to option to use either the RPCS driver (discontinued since the GW2009S controller), the PCL driver or the Postscript driver.

Both the RPCS and PCL driver can only output RGB data, while Postscript can output both RGB and CMYK data. So when printing CMYK data using an RPCS or PCL driver,

it will first be converted to RGB and then back to CMYK. The PCL driver is excellent for printing to high quality

(more than 4-color) inkjet printers because they must be driven by RGB data. They are not really CMYK because of the additional colors.

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Color Management in Printer Driver

Each manufacturer seems to decide a different color management approach for their printer driver.

However, most, if not all, Postscript drivers can use Postscript color management.

Most professionals will therefor prefer to use a Postscript driver.

Example of a Ricoh RPCS driver

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Postscript Color Spaces in PDF

For every PDF color space, there is an available Postscript color space.

And since PDF is widely used in the graphic arts market, this also explains why Postscript is the output file format for graphic arts applications.

A corresponding chart for PCL or RPCS would have too many gaps.

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In-RIP Color Management

Many printers have a Postscript interpreter built-in. This ensures true and predictable color. Even some applications are using a Postscript RIP.

For instance, Adobe InDesign uses the AGM or Adobe Graphics Model.

This is a Postscript RIP, which will “print” the document to the monitor.

This allows “true” WYSIWYG.

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Postscript Details

The Postscript driver can send RGB or CMYK data to the printer, but the data can be in CIE color space as well.

ICM can be used in 4 ways: ICM Disabled. ICM by Host. ICM by Printer. ICM using Printer Calibration.

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ICM

ICM Disabled means that color management is disabled. This is the preferred setting when you want color

management to be performed by the application (for instance Photoshop).

ICM by Host means that you will use the color management system of the Operating System. Make sure to attach the correct ICC profile to the printer.

If you select ICM by Printer or using Printer Calibration, the Postscript interpreter in the printer will actually do the color management.

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5.7 Color Controllers

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Color Controllers

Instead of relying on Operating Systems or applications, many professionals are now relying on the color management features of their printer controllers.

These controllers have a built-in Postscript interpreter and sometimes even a built-in PDF interpreter (Adobe PDF Print Engine).

Since many professional printers have made the switch to the PDF workflow, these controllers allow a very efficient PDF workflow.

Most professional color controllers like Fiery or Creo controllers are loaded with all sorts of advanced color management features.

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Color Controller Features

These controllers have support for: Calibration ICC Workflow Import of custom ICC

profiles Printing of spot colors Spot color editing Printing of separations Simulation printing Color substitution Printing of overprints Imposition Composition Preflights And many more

The next few slides will explain some of these features.

Example of a Fiery controller

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Simulation

Professional controller allow you to “simulate” another printer or printing standard.

Just an example: A lot of printing companies are now printing according to a

standard: ISO 12647, which allows printing companies to print predictable and consistent.

On Fiery and Creo controllers you can select an ISO standard profile as a simulation profile, thereby making the printer print according to the same standard.

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Overprint

In most cases, when two objects of different colors overlap they knockout -- they will not print on top of each other.

To intentionally print one layer of ink or toner on top of another is to overprint.

Overprinting is sometimes used to avoid the need for trapping and avoid gaps between touching colors.

Overprints can become really difficult to print when you use it in combination with transparencies. You will need a high end printer controller to print these sorts

of things.

Overprint without

transparency

Overprint with transparency and

drop shadowOverprint without transparency with

drop shadow

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Imposition

Imposition is one of the fundamental steps in the prepress printing process.

It consists in the arrangement of the printed pages on the printer’s sheet, in order to obtain faster printing, simplified binding and less waste of paper.

As an example, a 16-page book is prepared for printing. There are eight pages on the front of the sheet, and the

corresponding eight pages on the back. After printing, the paper is folded in half vertically, folded

again horizontally and folded for a third time. The example below shows the final result prior to binding

and trimming.

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Example of Imposition on a Fiery Controller

With a few mouse clicks, a 12 page PDF file can be printed as a document setup for saddle stitching.

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Preflight

Preflighting is usually the first step in prepress processing. Preflighting includes any and all standard prepress

document additions, font and color changes, and error corrections that can influence a job's passage through the workflow.

This allows you to check if a file can be printed correctly, without wasting time, paper and toner.

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Last Stage Editing

On professional controllers, last stage editing is possible. Think of color corrections, imposition, composition etc.

Since problems can be corrected at a very last stage, this can save valuable time and money. Files do not have to be send back to the creator, but can

instead be corrected on the controller.

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5.8 Prepress Solutions

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Prepress Solutions

Prepress solutions are basically proprietary modules that fit into a existing workflow.

Examples of popular systems are: Prinergy (Creo Kodak) Prinect (Heidelberg) Apogee (Agfa)

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Benefits

One benefit of using a prepress solution lies most of all in the automation of a workflow.

For example, errors which are detected by preflight can be automatically corrected, without any human intervention.

Another benefit is that it can offer the same workflow for both digital printing and offset printing (hybrid workflow).

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Downsides

Basically, there are 2 points to consider, when going for a prepress solution.

First, the price. It can be quit costly to implement a solution like this. In time, it will probably save money, but the initial costs can

be high. Second, knowledge.

Implementing the solution will most likely be done by the solution vendor, but even operating the solution requires a great deal of knowledge.

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6. Proofing

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What is Proofing?

Proofing is the simulation of the output of one device on another device, such as a printer (hard proofing or monitor (soft proofing).

Needless to say that whatever device you use, it must be properly calibrated, profiled and it must have a large enough color gamut.

Proofing is very popular in the offset world, because printing on an offset press is quite expensive and, generally, takes some time.

To fully understand proofing you will need a basic understanding of offset printing.

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Offset or Lithography Basics

The basic principles of offset printing: Ink is supplied to the plate

cylinder. The plate cylinder has an

etched metal or polyester plate. The etched parts of the plate are ink repellant, so the ink will only stick to some parts on the plate.

Ink from the metal plate will be transferred to the offset- or blanket cylinder , which is covered with a rubber blanket

Finally, ink is transferred from the offset cylinder onto paper.

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Multiple Colors

The previous slide showed just one color. To print multiple colors, you could either print one color

one paper, clean the offset press, remove the metal plate for the first color, attach the metal plate for the second color, fill the offset with the second ink, and start printing the second color on the same paper.

This is, of course, very time consuming, but still widely done.

Another option is to use an offset device with multiple print stations.

6-Station Man Roland 12-Station Heidelberg

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Plates

There are many ways in how to create the metal plates, but this is one of the most popular ones: The operator first creates an

image on a piece of transparent polyester (film negative).

The film is placed on top of the metal plate, which has a photo polymer coating.

The metal plate is then exposed to UV light.

The parts of the photographic layer that are exposed to UV light can be etched away using etching liquid.

The parts of the plate that are not etched away (the image) is water repellant but ink will stick to it.

The parts of the plate that are etched away are not water repellant. Because water will stick to this parts, ink will not.

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CTP or Computer To Plate

Relatively new is the CTP technology, which allows the imaging of metal or polyester plates without the use of film.

The benefits of CTP are: reduced prepress times. lower costs of labor. improved print quality.

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Full Color Printing

In offset printing, CMYK inks are used to create a full color print.

Additionally, spot inks may be used for spot color printing.

Black

CyanYellow

Magenta

Spot

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Screening

An important parameter in offset printing is screening. The screening frequency or halftone frequency is the

resolution of a halftone. It is the density of dots (how far they're spaced apart from

each other) measured in lines per inch. The screening frequency can be calculated using the

following formula: = Amount of gradations

Examples: engine resolution = 1200 dpi screen ruling = 90 lpi engine resolution = 1200 dpi screen ruling = 150 lpi

178 gradations

48 gradations

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Screening Techniques

The 2 most used screening methods are: AM Screening:

Varying dot sizes, used by conventional presses

This type of screening produces good quality “flat tints”, however lacks the fine detail that can be produced by “FM” screening.

FM Screening: Also called stochastic

screening. Uses small dots with fixed

size, but with varying spaces between the dots.

This type of screen produces sharp detail, however it usually produces graininess in flat tint areas and is less responsive on press than “AM” screening in making slight color moves.

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Hybrid Screening

Hybrid screening is a mix of AM and FM screening, taking advantage of their pros while minimizing their cons.

Hybrid Screening is not a simple combination of screens, but a true hybrid of two screens.

The transition from one screen to the other screen occurs over a range of grey levels in such a way that it is not visible to the observer.

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Screen Angles

The screen angle is the angle at which the individual dots are printed.

A black and white halftone image consists of a single screen.

The screen pattern is very noticeable when positioned at 0° and is least visible when rotated 45° as illustrated below.

For that reason, black and white halftones are usually printed with 45° angled screens – particularly with coarser screens.

45°0°

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Moire

When two or more screens are printed on top of each another, a pattern known as moiré may appear.

The most serious moiré patterns occur at very small angles between screens.

The best angle between two screens that is least likely to cause moiré, and is most forgiving to small degrees of error, is 45°.

However, in four color process printing, four different screens must be superimposed and all four screens must be angled within the 90° limitation.

5° 10°

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4 Colors

Based on theory and experience, a standard set of screen angles has been established for 4-color printing: The least visible color, yellow, is placed at the most visible

angle (0°, 90°). The most visible color, black, is placed at the least visible

angle (45°). Cyan and magenta are placed in between them with angles

of 15°/105° and 75°.

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CMYK and Spot

CMYK and one ore more spot colors presents a problem. Basically, you do not have any angles left for the spot

color. The basic rule is to use the screen angle of the least

prominent (or missing) screened process color that will be underneath the screened spot color.

However, this not always possible.

Cyan overprinted with yellow

Cyan overprinted with PMS144 with yellow screen angle

Cyan overprinted with PMS144 with magenta screen angle

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Dot Shape

Another important parameter in offset printing is the dot shape.

The 3 most used shapes are elliptical, round and square. Of these 3, the most common is the elliptical dot that gives

smoother midtones, compared to the round and square dots.

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Dot Gain (1/2)

"Dot gain" is the term that is used to describe the difference between the requested tone value in the original application file and the resulting apparent final tone value on the substrate as measured with a densitometer.

On the next slide, you can see the alteration of halftone dots as they move through each stage of the offset printing process.

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Dot Gain (2/2)

When a tone value is requested, for example, in a page layout application

it becomes represented by a halftone dot pattern generated in prepress by the workflow RIP

which is then imaged onto a printing plate

which is then inked

and transferred under pressure to the blanket

from which, again under pressure, the inked dots are transferred to paper

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Countermeasure Dot Gain

Actually, there is no real countermeasure for dot gain, since it is simply a characteristic of a process that uses pressure to transfer an ink to a substrate.

The dot gain is highly dependent on the used machine, the used inks and the used substrate.

What operators do is simply measure the amount of dot gain for a given tone value.

Then, in the page layout software, they lower the requested tone value, so that the requested tone value + dot gain gives the wanted tone value.

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Back to Proofing

As you can see, in offset printing there are quit a few parameters involved. Please note that the previous slides just showed a few. In real life offset printing, there is a lot more to think about.

When you want to use a laser printer for proofing, the laser printer should be capable of mimicking most of these parameters.

Examples: You may want to be able to change the screening to check

for moiré artifacts. You may want to be able to set dot gain to check what will

happen with a given requested tone value. Usually, this sort of things are only possible on

professional color controllers like (Creo, Fiery).

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Proofing to a Standard

You can proof another device, by selecting the ICC output profile of the device, and use it as a simulation profile on a Creo or Fiery.

However, more and more popular is actually proofing to a standard.

A lot of printing companies have their devices (both offset and digital printers) certified for printing to a standard, for instance an ISO standard.

If the offset is certified for ISO Coated, just select the ISO Coated ICC profile as a simulation profile on the laser printer.

The next slide shows an example.

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Proofing Example

In this example, you can see a Fiery controller, setup for CMYK simulation of the ISO Coated standard.

The ISO Coated ICC profile is used as a simulation profile.

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Important Notes

If you want to use a laser printer as a proofing device, there are a few things to consider.

First of all, the proofing device must have a large gamut, since it needs to be able to print (almost) all the colors that the offset can print. This can proof to be very difficult, especially when printing

spot colors. Another important note is that the proofing device needs

to perform at its peak. It needs to be regularly calibrated to maintain its output

quality and it needs to be well maintained. It needs an output profile for all media that is printed on.

This can be done through profiling.

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7. Profiling

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What is Profiling?

Profiling is the process of custom-made creating ICC profiles.

These profiles can, depending on their purpose, be used for simulation or as output profiles. You can create profiles for other devices and use them as

simulation profiles. You can create profiles for your laser printer for different

media types and use them as output profiles.

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Benefits of Profiling

Most professional controllers are shipped with some default output profiles for several media types (plain, gloss coated, matte coated).

However, since you do not know what media was used to create those profiles, and since these profiles were not created for your device, the default profiles may not give you the best results. In most cases, the default profiles are created by profiling

several machines, and then averaging the results. The get the best out of your device, you should create the

profiles on your media and for your device.

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Profiling in a Nutshell

Profiling basically consists of: Printing patches on the device you want to proof (simulation

profile) or on the proofer (output profile). Measuring the patches with an photo spectrometer. Convert the measurements into an output profile Install the output profile on the printer controller of the

proofer.

Maintain Color by Calibrating at the Fiery

Print combined calibration & profile patches

Measure Patches with ES1000 or

i1iO Scanning Table

Automatically install new profile on the Fiery

Use Profile Inspector to Accept Profile

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Profiling Software

To create profiles you will need software and hardware. From the company X-Rite, for instance, you can buy the

“X-Rite ProfileMaker 5 Platinum i1Pro Color Calibration System Bundle for Mac & Windows”, which contains software (Profile Maker 5 Pro) and hardware (i1 photo spectrometer).

With a price tag of nearly 2500 dollars, it is not exactly cheap, but quality comes at a price.

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Color Profiler Suite

The EFI Color Profiler Suite comes at a more reasonable price of around 1500 euro.

It includes the same i1 photo spectrometer, but then called ES-1000, and EFI-made profiling software.

It allows you to create printer profiles (for simulation and output), monitor profiles (crt, lcd) and device links, inspect and edit profiles and to measure control bars.

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Profiling Service

If you do not want to invest in profiling software, you can also find companies on the internet who offer a profiling service.

In most cases you will be asked to download some software and patch page(s) which you have to print on your color printer.

You send the printed page(s) back to this profiling company and they will create a profile for you.

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Profile Tweaking

Creating profiles for your machine and your media will not always produce the output you want.

The created profiles will accurately describe the behavior of the machine, but sometimes you may have to tweak the profiles a bit depending on your print job. Think of printing a black cat with enough detail in de shadow

areas or a polar bear with enough detail in the highlights.

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Profiling on WICE

If you want to know more about profiling, you can find a training module on WICE about the EFI Color Profiler Suite.

Color Profiler Suite v2 on WICE, soon to be replaced with v3

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Basic Color ManagementEND