PHOTOSHOP system settings and discussion (on)

The most important reason for the impact of color-accurate print copying is that the display's RGB color gamut differs from the printing ink's CMYK color gamut from the printing ink's CMYK color gamut, and the color will eventually differ depending on the output device and application software. For example, from one monitor to another, from one printer to another printer, file transfer between different software, etc., different results are obtained, so monitor adjustments, materials, etc. are required before designing using an electronic publishing system. Parameter settings, color separation settings, dot gain compensation schemes, and a series of system setup preparations.

This article discusses several issues involved in the system setting in the Apple system PHOTOSHOP5, and discusses some issues in more detail and makes more reasonable settings. The setting method of the PC using the WINDOWS95/98 operating system is similar.

First, the display settings and adjustments

Image correction is performed in ADOBE PHOTOSHOP to ensure that the colors displayed on the screen are consistent with the colors obtained by printing. To obtain what you see on the screen is the result of the final printing, you need to make a series of corrections. Calibrate the monitor first to adapt to the teletext system environment.

Adjusting the PHOTOSHOP's display settings will affect the on-screen display and image color mode conversion process. The image is displayed on the screen in RGB color mode. If the color mode of the image is CMYK, the color mode needs to be converted to RGB before it can be displayed on the screen. The display setting only affects the display effect of the image. Affects the data of the CMYK image; if the image is in the RGB mode, when the image is converted to the CMYK mode, different color separation data will be obtained due to the different display settings.

1, GAMMA settings

The GAMMA settings for the display are generally made through the ADOBE GAMMA control board, which can be found in the "Control Panel" in the Apple system.
Through the ADOBE GAMMA settings can produce a device description file that conforms to the ICC standard. There are two sets of ConTROL PANEL or step by step (STEP BY STEP, ASSISTANT) settings.

If you select ConTROL PANEL, multiple control boards are set up to be set up at the same time. See Figure 2. I input the device description file in turn, I said, adjust the brightness and contrast, select the monitor phosphor model, the GAMMA initial value and fine-tuning, white field settings. STEP BY STEP is the same as ConTROL PANEL. It can only be set up step by step with the help of a wizard.

First, adjust the brightness and contrast of the monitor. Set the contrast to the maximum and adjust the brightness so that the small square in the middle is as dark as possible.

In the second step, select the type of phosphor used by the monitor. Most monitors use the TRINION standard.

The third step is to set and fine tune GAMMA values. The apple system selects MACINTOSH DEFAULT under GAMMA, which means the GAMMA value is set at 1.8. Then fine-tune the slider to make the gray value of the central area of ​​the square look the same as the gray value of the surrounding area. When performing fine adjustment, a single grayscale block or RGB three-color grayscale block can be displayed to adjust each color.

The fourth step is to determine the white field color temperature of the displayed hardware. When you know the color temperature of your monitor, you can choose the appropriate value.

You can also click "MEASURE" at this point and select it visually. The screen will turn black, and every day a square, at this time choose the most neutral one. Setting the display to a cooler or warmer color temperature by clicking on the left or right squares is done when the middle box is clicked.

The first step is to adjust the color temperature in the work field. You can select a value that matches the hardware setting of the display to match the hardware setting or choose a different value to adjust the monitor display.

Finally, complete the GAMMA settings, select BEFORE or AFTER to observe the changes before and after the GAMMA setup, enter the file name, and click FINISH to save the settings.

If you use a MACINTOSH machine and have a third-party monitor calibration program, either use a third-party program or use the tools provided by PHOTOSHOP instead of using both. Because the third-party program updates the PHOTOSHOP color space description file, if both are used, the basic parameters of some displays may be set through PHOTPSHOP 5 FILE - COLOR - STEENINGS - RGB SETUP. The setting parameters made are the same as those set by GAMMA.

Second, the ink parameters and separation settings

In PHOTOSHOP 5 software, use FILE - COLOR SETTINGS - CMYK SETUP to set the ink and paper number and separation settings.

1, custom paper and ink parameters

In the CMYK SETUP dialog box, select the ink type used in the INK COLORS drop-down list. The default setting is to select SWOP(COATED) for INK COLORS. The dot gain value at the 50% dot is set to 20%. If the ink used is not available in the drop-down list, such as the inks in places such as Tianjin and Shanghai, the color parameters of the various inks need to be obtained by testing and proofing. Then select the custom INK XOLORS in the dialog box, input the color coordinate value of each color block, and re-dot GAIN value. The same ink parameters as the monitor settings will affect the image color mode conversion, such as the GRB-CMYK mode conversion. If the ink parameter is set after the image is converted to CMYK mode, the parameter setting only affects the display of the image.

We used Tianjin Tiens GS series ink in the experiment, so when the film was exported for the first time in the experiment, there was no ink parameter used, and the ink type (SWOP COATED) was selected. After the output proofing, the ink parameters used were tested. The actual ink and paper parameters are entered into the PHOTOSHOP software to replace the original settings so that the future RGB images can be accurately separated. Follow the steps below to adjust the custom ink paper parameter values.

(1) Use the PHOTOSHOP menu command FILE - COLOR SETTINGS/CMYK SETUP to bring up the setup dialog.

(2) Select CUSTOM under the INK COLORS drop-down menu in the dialog box to customize the input of the ink paper parameters.

The dialog box shows the ink color of different CMYK combinations and the spring CIE chromaticity coordinates. The CIE chromaticity coordinates are the color definition standards supported by POSTscript. The ink and paper parameters in the ink dialog box are Y (brightness), X-Y (chromaticity) Coordinates) are expressed as values. The chromaticity value of the ink is measured with a colorimeter under standard observation conditions of a D65 light source and a 2 degree field of view. If there is no colorimeter, the color of the color patch can be adjusted to the color of the proof by visual means. The figure shows the data obtained from the proofs printed with Tianjin Ink. The luminance values ​​and the chromaticity coordinates of the solid patches, such as yellow, yellow, green, yellow, yellow, green, white, black, and yellow, plus yellow, measured from the printed sample sheet, are input into the corresponding text box. .

In most cases, the ink will not produce a large hue difference on the same type of printer or printer, but it may produce some dot gain differences. Therefore, it is generally not necessary to perform ink re-setting for another printer or printer of the same type, and it is only necessary to change the DOT GAIN value in the setting dialog box. With a series of image adjustment means, the belt can make the image display effect be the same as the color of the printed proofs, achieving the effect that the screen sees and prints.