Print Color Management — Creation of Monitor Profiles

Print Color Management — Creation of Monitor Profiles

Table of content.

I. Basic Principles and Requirements:

In desktop systems, monitors are used as a soft-proofing tool. Image colors are adjusted based on screen display, therefore it is crucial to make the monitor display effect as close as possible to the final proof or printed output.

During this process, monitor calibration is achieved by adjusting brightness, contrast, color balance, Gamma value, and light source color temperature.

 

 

II. Experimental Instruments:

1. Computer Equipped with CRT or LCD Monitor and Monitor Hood

CRT is the abbreviation for Cathode Ray Tube.

A CRT monitor, whose full Chinese name is “Cathode Ray Tube Display,” is a display device that uses a cathode ray tube as its core imaging component. It was the dominant display technology for early computers, televisions, radar screens, and other devices before LCD monitors became widespread. In simple terms, it is what we commonly called the “big-back” monitor or “picture tube” monitor, because of its large and thick glass back.

 

 

CRT Color Rendering Principle:

The basic principle of a CRT monitor is to use an electron beam to strike phosphors on the screen, causing them to emit light and form images. The detailed steps are as follows:

Electron Gun Emission:
 At the rear of the CRT tube neck, there is one or more electron guns. When heated, they emit fine electron beams.

Acceleration and Focusing:
 A high-voltage electric field accelerates the electron beams, and electromagnetic lenses focus them into a very fine point.

Deflection Scanning:
 Deflection coils are placed around the CRT neck. By generating changing magnetic fields, they control the electron beam to scan across the screen from left to right and from top to bottom in a regular pattern (this scanning method is called raster scanning).

Phosphor Excitation:
 The inner surface of the display screen is coated with phosphor dots or stripes of red, green, and blue. When struck by high-energy electron beams, these phosphors emit corresponding colored light.

Image Formation:
 For monochrome CRTs, a single electron gun controls brightness to produce black-and-white images.
 For color CRTs, there are typically three electron guns (or one gun emitting three beams), corresponding to red, green, and blue (RGB) primary colors. By controlling the intensity of the three beams and mixing RGB in different proportions, a full-color image is produced.

CRT monitors display colors based on the RGB color space. Because manufacturers use different phosphors, and because color reproduction relies on additive color mixing, red, green, and blue phosphors serve as the primary colors for image formation.

 

 

LCD Color Rendering Principle:

LCD stands for Liquid Crystal Display.

Liquid refers to the fluidity of the material.
 Crystal refers to the ordered molecular structure similar to that of a solid crystal.

Liquid crystals are special substances between liquids and solids. They possess both fluidity and optical anisotropy (meaning physical properties such as refractive index differ depending on direction).

 

 

LCD Color Formation Principle

An LCD screen, also called a liquid crystal panel, is similar to a CRT in that each frame consists of many pixels. Each pixel can be regarded as a small liquid crystal cell. Pixel coordinates are defined by X and Y axes, forming a matrix display.

The structure of a color LCD includes polarizers, liquid crystal cells, color filters, and a backlight source.
 Twisted Nematic (TN) liquid crystal materials are commonly used.

The color formation principle of LCD can be summarized as follows: electric current controls the arrangement of liquid crystal molecules, which determines whether light passes through. Combined with color filters, the final image is formed.

The core steps are:

Backlight Module:
 LCDs do not emit light themselves and require a backlight source (usually LED) to provide uniform white light.

Polarizers:
 Two polarizing plates are placed in front of and behind the liquid crystal layer. They only allow light of specific vibration directions to pass. The two polarizers are typically arranged perpendicular to each other.

Liquid Crystal Layer:
 Located between two glass substrates, containing millions of tiny liquid crystal units (each corresponding to a pixel).

Transparent Electrodes:
 Located on the glass substrates, used to apply voltage and create electric fields.

Color Filters:
 Each pixel consists of red, green, and blue subpixels, each covered with corresponding RGB color filters.

 

 

2. ProfileMaker (Profile Creation Software) or EyeOne Match (Profile Creation Software)

3. EyeOne Spectrophotometer

 

 

III. Experimental Steps:

(I) Preparation Before Calibration and Characterization

  1. Turn on the monitor and start the computer. Allow the monitor to warm up for at least 30 minutes.

  2. Set the monitor’s screen resolution, refresh rate, and color quality.
     Set the screen resolution to commonly used values, such as 1280 × 1024.
     Set the refresh rate to 75 Hz or above to ensure better display quality.
     Set color quality to 24-bit full color.
     If any of these parameters change, the monitor must be recalibrated.

  3. Clean the screen and ensure there is no dust or fingerprint residue.

  4. Turn off strong surrounding light sources. It is best to use a monitor hood. Disable screen savers, and set the desktop background to 20% gray, as shown in the figure.

(II) Monitor Calibration and Characterization

  1. After launching the ProfileMaker software, select MONITOR, as shown in the figure:

 

  1. Perform a series of parameter settings as follows:

(1) Select the type of monitor you are using:

Choose CRT Monitor Reference.txt or LCD Monitor Reference 2.0.txt, as shown in the figure:

 

(2) Select your measurement device.

Supported devices include EyeOne, Spectrolino, and Monitor Optimizer.
 Here, EyeOne is used, as shown in the figure:

The system requires placing the measuring instrument on its base at the standard white reference point to calibrate the instrument’s standard white, as shown in the figure:

Select “OK”, and the software will prompt you whether to perform monitor measurement, as shown in the figure:

Select “Yes” to start the monitor measurement function, as shown in the figure:

 

(3) Set the White Point

There are many color temperature options for the white point, as shown in the figure:

Generally, 5000K or 6500K is selected.
 In China, the standard printing light source is specified as 6500K, while the international standard commonly uses 5000K.

If you evaluate printed proofs in a standard light booth, 5000K may be used.
 For general indoor viewing, 6500K is more suitable and conforms better to human visual habits.

 

 

(4) Set the GAMMA value

For PC systems, use 2.2; for MAC systems, use 1.8, as shown in the figure:

Brightness is recommended at 100%.
 Select the type of monitor you are using; here, an LCD monitor is selected, as shown in the figure.

After setting, click the small arrow below to proceed to the next step.

 

(5) Contrast Adjustment

First, adjust the monitor contrast to maximum.
 Then click Start, and slowly adjust the monitor’s contrast setting until the upper and lower arrows align, as shown in the figure:

Click Stop and proceed to the next step.

 

 

(6) White Point Color Temperature Adjustment

As shown in the figure:

Adjust the RGB values of the monitor separately, aligning the three color arrows as closely as possible.

If precise alignment is difficult, a green checkmark is acceptable.

If all RGB values are adjusted to maximum or minimum and the required color temperature still cannot be achieved, it indicates that the monitor is excessively aged and should be replaced.

After adjustment meets the requirements, proceed to the next step.

 

 

(7) Monitor Brightness Adjustment

Set the monitor brightness to the minimum, then gradually increase it until the upper and lower arrows align, as shown in the figure:

For unstable monitors, it may be difficult to align brightness precisely. The indicator may fluctuate. Carefully adjust to ensure the arrows are as close as possible.

Once the requirement is met, proceed to the next step.

 

 

(8) Start Automatic Measurement of 42 Standard Colors

This step is very important. It measures and generates the monitor ICC profile.

 

(9) After automatic measurement is completed

The system will prompt whether to save the measurement data, as shown in the figure:

Select “Yes” to save the measurement data.
 After saving, the software loads the measurement data just created, as shown in the figure:

 

(10) Profile Size Selection

Select “Large” for profile size to generate a larger ICC file, providing higher accuracy.

Select D65 for White Point (the white point you just set), then click “Start” to begin calculation.

 

(11) Save the ICC File

You will be prompted to save the ICC file.

After calculation and saving are complete, the system will ask whether to use the generated ICC file as the monitor’s system profile, as shown in the figure:

Select “Yes”, and the ICC profile will automatically be loaded as your monitor’s color management file.

You can verify this in Display Settings → Advanced → Color Management.

 

 

IV. Viewing the Gamut of the Created ICC Profile

You can use ProfileEditor to view the gamut of the generated ICC file.
 Open ProfileEditor, as shown in the figure:

 

(1) Click “GamutView”

This opens the gamut viewing function.
 Click “Open”, and load the ICC file generated after monitor calibration, as shown in the figure:

 

(2) Gamut Display Options

There are four display options: 3D (Lab), 2D (ab), 2D (uv), 2D (xy)

Use these four options to view the generated ICC gamut, as shown in the figures:

                                                                             3D (Lab)

2D (ab)

2D (uv)

2D (xy)

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