Display principle and soft proofing

The display is the most important device in our prepress work for observing colors and determining the layout. This theme should be said to be the most practical, practical and important. I believe that in the future, we may gradually realize the reasons we started with the display. I hope that in the actual work, we will first give it its color from the monitor, so that in the future we can get a lot of benefits from the display.

First introduce the background of the display. The display is one of the most important and most frequently used devices in the prepress system. The display is a tool for the operator to obtain the production information directly. The displayed content is the first basis for the production and design personnel. The effect of the monitor is directly related to the effect of prepress production and is the primary target of color management. However, the color management of displays has great difficulty.

Although the color rendering principle of the display is much simpler than that of a printer scanner, it is the most difficult for the display to be consistent with our actual printing sample because the display is not the same as the way we normally observe prints. For such a device, I have previously done some monitor adjustments to the enterprise, but people always reflect the monitor. It is a kind of luminous device. Observing the printed matter is always to be observed under the external lighting source when comparing the prints. Always feel unsatisfied with tune, another is that the color gamut displayed by the monitor is not exactly the same as the color gamut of our prints. People are concerned that there are a lot of colors on the monitor that can be displayed on the real and printed materials. The actual colors are in line with each other, which requires us to first understand the color rendering principle of the display.

Display Types and Features

Currently, there are two kinds of monitors that are widely used: cathode ray tube displays (CRTs) and liquid crystal displays (LCDs). From the current application perspective, in our printing industry, CRT displays still dominate, but LCD monitors are small and low-cost. Radiation, stability, continuous improvement of quality, and continuous decline in prices have been rapidly popularized. The development is faster and faster, and the proportion of use is also increasing. LCD monitors are preferred by soft-proofing manufacturers. At present, monitors used for remote proofing are all LCD monitors, and basically do not use CRT monitors. Although there are other display technologies from the display technology, such as plasma, electroluminescence, and some people even predict that the caller system will become an alternative technology, but it is still practical in these two.

The principle of CRT display

The luminous intensity of a phosphor is proportional to the number of electrons. By controlling the number of electrons emitted by the three electron guns, thereby controlling the luminous intensity of the RGB phosphors, the CRT display displays the phosphors by emitting electron beams.

Based on the above principles, we summarize the following points:

CRT monitors are affected by magnetic fields

Electron beam is easily uneven on the entire display screen, resulting in poor display uniformity

The brightness of the display is determined by the brightness of the phosphor. Aging of the phosphor will reduce the display brightness and the contrast will not be high enough.

The color gamut of a CRT monitor is relatively wide, which is close to the color gamut of printing inks.

The principle of LCD display

The LCD display is a sandwich-type structure in which a layer of liquid crystal is sandwiched between two glass plates. Behind the liquid crystal layer is a backlight lighting plate. The function of the liquid crystal is to control whether or not the backlight can transmit through the dye filter, so that the through The light is red, green and blue primary colors. The three primary colors are mixed to display colors. The intensity of transmitted light can control the number of primary colors.

LCD display features:

Does not require high voltage deflection electric field, radiation is small;

Brightness, contrast higher than CRT monitors;

The display on the screen is even;

There is no problem of aging of the phosphor, the backlight can always be brighter;

There are limitations of the observation angle;

In principle, the display contrast and the three primary colors cannot be adjusted;

The price is higher than the CRT;

Monitor calibration:

From the point of view of color mixing, the principle of color mixing of the two monitors is the same;

The factors that determine the color of the monitor: the monitor and the display card;

The key factors for calibrating the display are: white field color temperature (determining the ratio of the three primary colors) and gamma (determination of the display tone level);

Whitefield should try to adjust through the display hardware;

Monitor calibration and color management:

Display calibration and color management is usually done in the same software

The process prior to color measurement is calibration, color measurement, and generation profile

The calibration of the display is a color management process, so the key to the color management of the display is to calibrate the display because the color management is only a record of the state of the device and cannot change the state of the device.

Soft proofing problems to be solved

Digital proofing is based on color management. The basis of color management is the stability and standardization of the production process to ensure the consistency of color. The key to the stability and standardization of the production process is management. It is a systematic project.

The trend in digital proofing today is remote proofing. The printing industry is an information service industry that is tending to internationalization and is breaking geographical restrictions. Remote proofing is based on the development of the network and meets the needs of real-time and remote sites. The best solution for remote proofing is soft proofing. Kodak and ICS have already launched remote proofing software.

Technical problems to be solved in remote proofing: network data transmission and data compression. At present, network speed can be practical and there are various mature compression algorithms. Editing, editing and communication of remote proofing are easier to implement on the Internet. The color consistency has two meanings: the consistency of the soft proofing and the printed color, and the consistency between the soft proofing devices. All the consistency must be achieved by color management. The monitor must be quality-certified, and its performance should be similar to the printed color effect.

The current SWOP certified monitors include: APPLE CINEMA, EIZO CG series, SONY DSM P232W/B. Need to be equipped with corresponding measuring instruments to ensure the monitor's color is accurate

Remote signing:

Confirm the rights and validity of the sample on the internet;

Many parties can communicate in real time, modify the proofs, and approve the proofs;

Simultaneous display to ensure that all parties see the same content;

The final signing has legal effect;

Note: This article is a summary of the speeches in the theme of "Color Management of Monitors and Screen Soft Proofing" organized by Color Club of Beijing Institute of Printing. It is for reference only.

Author: Liu Beijing Institute of Graphic Communication Studies