(1) Color Management System

 

Reasons for Color Management

★ A color management system ensures that the reproduced colors match the original as closely as possible.

★ Consistency and predictability are crucial in color reproduction.

★ The simplest way to reduce variations in color is to standardize wherever possible.

Color Management System

1. Color Matching

Adjusting digital devices to reproduce the same colors is called color matching.

Most of the work in color management involves achieving consistent color matching.

2. PCS (Profile Connection Space)

A device-dependent color space is the space used to connect device profiles.

Therefore, it is called the PCS (Profile Connection Space).

☆ Device-dependent colors → dialects in a closed system

☆ Device-independent colors → universal language

☆ Device profile → translation dictionary

  (dialects → universal language)

  (universal language → dialects)

3. ColorSync and ICM Systems

In Windows and Macintosh systems, the following color management systems are pre-installed:

* Windows: ICM 2.0

* Macintosh: ColorSync 3.0

When using the operating system’s built-in color management functions, the dedicated color-matching systems from application developers are not used.

4. Core Components of Color Management

▲ A device-independent color space is required as the intermediary for color conversion between different devices.

▲ Each device must have a standard specification that describes its color reproduction capability, characteristics, and parameters.

 This is stored as a profile file.

▲ A precise algorithm is required to perform color conversion between different color spaces.

5. Overview of the Color Management Process

Color management involves three major steps:

1) Calibration

A method to adjust each device to a defined standard state, ensuring that it meets or is close to the manufacturer’s specifications.

Devices constantly change over time, which affects how color is displayed and reproduced, so calibration is essential.

All devices must be calibrated before use to ensure proper performance, similar to the "zero calibration" of measuring instruments.

2) Characterization

Every device has its own color reproduction capability.

Characterization determines the device’s color gamut and records its characteristics mathematically, so that color conversions can be performed accurately.

3) Conversion

Since each device has a different color gamut, color conversion does not provide 100% identical color reproduction.

Instead, it produces the best color output the device can achieve while allowing users to predict the final results.

 

(2) Color Calibration

1. What factors affect color output?

▲Environment (temperature, humidity)

▲Materials

▲Screening method and shape

▲Specific settings of the engine

▲Toner and carrier

▲Operating time of the engine

2. Functions of Calibration

☆ Verify the engine status

☆ Adjust the engine’s output linearity

☆ Ensure the engine’s color gamut is maximized

☆ Minimize color deviation in the engine’s output as much as possible

3. Relationship between Calibration and CMS (Color Management System)

Calibration and the Color Management System (CMS) work together to ensure consistent and predictable color output across different devices. Their relationship can be summarized as follows:

Calibration is the foundation of color management.

  It ensures that each device (printer, monitor, scanner, etc.) operates in a stable, standardized condition. Without proper calibration, color management cannot accurately compensate for device behavior.

Calibration defines the device’s baseline performance.

  By adjusting linearity, density, and color balance, calibration brings the device to a known, repeatable state. This allows the CMS to interpret the device’s color response correctly.

CMS relies on calibrated devices to build accurate profiles.

  Device profiling (characterization) measures the color output *after* calibration. If the device is not calibrated, the profile will be inaccurate, and color conversion will not produce reliable results.

Calibration minimizes internal variability, while CMS manages cross-device differences.

  * Calibration reduces fluctuations within the same device (day-to-day drift).

  * CMS manages differences between different devices (monitor vs. printer, printer A vs. printer B).

Accurate color conversion requires both processes.

  Calibration stabilizes the device, and CMS uses the device profile to map colors precisely between different color spaces.

In summary:

Calibration ensures consistency; CMS ensures color accuracy and predictability across devices.

4. Color Measurement Devices

Color measurement is necessary for device calibration. Devices used to measure color are called color measurement instruments. These instruments are classified into two types: contact and non-contact.

▲Contact devices:

Used when the measurement contact does not change the color of the target object.

Example: Copy output from a printer.

▲Non-contact devices:

Used when the measurement contact would change the color of the target object.

Example: LCD displays.

Color Management Fundamentals—(3) Personalization

1. ICC

ICC refers to the standard of the International Color Consortium.

The ICC (International Color Consortium) was established in the 1990s by a group of experts to create a standardized method for converting color information.

In printing workflows, each device has different color reproduction capabilities. To solve the problem of color inconsistency, several companies — including Apple, Adobe, Agfa, Kodak, and Microsoft — founded the ICC in 1993. This organization defined an international standard for Color Management Systems (CMS).

Today, it has become an industry-wide standard and is widely used.

The ICC Profile format is a flexible file format used to store the data in the tables mentioned above.

An ICC Profile describes what the actual color produced by a device corresponds to within a standard color space.

With the help of a device-independent color space (PCS) as the conversion intermediary, connections are built between RGB, CMYK, and PCS to create ICC Profiles for devices, enabling open and device-independent color management.

This allows color reproduction without relying solely on specific hardware.

Note:

An ICC Profile itself does not have the ability to change the original color data values generated by a device.

2. ICC Profile

3. Types of Profiles

Profiles can be generally divided into two categories:

★ Device Profiles:

Describe the color characteristics of a specific digital imaging device.

★ Profile-Based (Conversion) Profiles:

Used for color conversion across different types of devices.

Type	Usage Method
Device Association Profile	Defined for one-way conversion between color digital devices.
Color Domain Profile	Define virtual color space, such as Lab or XYZ.
Abstract Profile	Defined internally within PCS for color conversion.
Named color profile	Various colors defined as PCS values and device values.

4. Inside a Color Profile

 A lookup table of RGB values sent to a display based on CIE LAB values.

Colors	RGB	CIE LAB
Red	203,0,23	50,71,54
Darkish Blue	0,46,160	32,34,-71
Yellow	255,243, 0	95,-17,99
Green	0,139,74	56,-81,32

 A lookup table of CMYK values sent to a printer based on CIE LAB values.

Colors	CMYK	CIE LAB
Red	0,100,91, 0	50,71,54
Darkish Blue	100,69,0,    0	32,34,-71
Yellow	6,0,91,0	95,-17,99
Green	100,0,79,    0	56,-81,32

5. Link Profiles

 ★Establish the relationship between CMYK printer colors and RGB monitor colors.

 ★The more data points stored in the table, the more accurate the color matching performance.

Colors	RGB	CIE LAB	CMYK
Red	203,0,23	50,71,54	0,100,91,0
Darkish Blue	0,46,160	32,34,-71	100,69,0,0
Yellow	255,243,0	95,-17,99	6,0,91,0
Green	0,139,74	56,-81,32	100,0,79,9

6. Device Profile

 ■To accurately convert monitor colors into Lab data, gamma and white-balance information must be added to the RGB data.

 ■The mapping tables for color conversion — containing device characteristics and color values — are known as device profiles.

7. Basic Workflow of ICC Profiles

The ICC (International Color Consortium) is an organization responsible for standardizing color management.

The current standard format for device profiles defined by the ICC is known as the ICC Profile.

An ICC profile generally contains the following information:

▲ Input Direction: Device Color (RGB / CMYK) → PCS

▲ Output Direction: PCS → Device Color (RGB / CMYK)

▲ Additional Information:

PCS (Profile Connection Space) refers to a device-independent color space.

PCS is defined as follows:

 ▲Illuminant: CIE Standard Illuminant D50

 ▲Color Space: CIE XYZ or CIE L*a*b*

8. Color Gamut Differences Among Devices

Different devices have different color gamuts.

For the same CMYK data, four different devices may produce four different results.

9. Color Output Consistency

By using ICC Profiles, we can adjust CMYK values for different devices to achieve the most consistent color output possible across various equipment.