The continuous adjustment of pictures to be copied into halftone prints requires many steps, such as scanning, display, conversion from RGB mode to CMYK mode, output, proofing, printing, printing, etc., among which there are many variables affecting the tone reproduction effect, Errors in any link will lead to abandonment of previous achievements. To control the image tone reproduction to have a perfect effect, many bad factors must be eliminated, and the necessary parameter detection and correction methods must be adopted for each link. This article makes relevant settings on the PC to make the pre-press production meet the actual production requirements.
1. Calibration of the monitor
Perform image correction in Photoshop 6.0. In order to ensure that the color tone displayed on the monitor screen is predictable, the monitor must be calibrated. Two items to be noted when calibrating the monitor: the ambient light source should be standard, professional fluorescent tubes can be used, and the same as the sample light source in the printing workshop; It takes a period of time, at least half an hour, after the display is stable and then calibrate.
1. Determine the screen color space through Gamma setting
A Gamma program is bundled in Photoshop 6.0, which can be found in the control panel. Through the setting of Gamma, a device description file conforming to the ICC standard can be generated. There are two methods for centralized setting or following the wizard. See Figure 1 Gamma control panel, we can load the known ICC characteristic file as a starting point, or we can rename a file, we can adjust the brightness and contrast in this palette, select the model of the monitor phosphor, and set the Gamma value. And fine-tuning, white settings.
If you follow the wizard to set, you can follow the steps below:
Adjust the brightness and contrast of the monitor. Adjust the contrast to the maximum, and then adjust the brightness to make the small square in the middle as dark as possible.
Select the model of phosphor used in the monitor. Most monitors use the Triniton standard.
Gamma value setting and fine-tuning. The Gamma value is essentially the overall correction value of the display contrast. If it is used in printing settings, it is set to 2.2, because the density value reflected on the paper according to the printing ink is basically this value. Then fine-tune the slider so that the gray value in the center area of ​​the square looks consistent with the gray value around. When fine-tuning, a single gray block or RGB three-color gray block can be displayed to adjust each color.
Determine the white field color temperature of the display hardware. The white field value essentially refers to the appearance of white in the display. The white field color temperature of the display should be the same as the color temperature of the ambient light source, ie D65. You can also click "Measure" to select visually. The screen will turn black, and three squares will appear. At this time, select the most neutral one. Setting the display to a cooler or warmer color temperature by tapping the left or right square; the setting is complete when the middle square is clicked.
Adjust the color temperature of the working white field. You can select the same value as the display hardware setting to make it consistent with the hardware setting or select a different value to adjust the display mode of the display.
Complete Gamma setting, select Before or After to observe the display changes before and after Gamma setting. Enter the file name and click Finish to save the settings made for later recall.
2. The RGB setting determines the photoshop working color space
Through Photoshop 6.0 editing-color settings-custom RGB settings can set some of the most basic parameters of the monitor. The setting parameters are the same as the values ​​set by Gamma, so that the Photoshop color space is consistent with the monitor color space.
Second, the test of the scanner
Most scanners have been calibrated at the factory, but due to differences in manufacturing conditions, changes in the color temperature of the light source, new and old, etc. will affect the pointer of the scanner. When purchasing a flatbed scanner, manufacturers usually provide a standard transmission or reflection manuscript, which includes a neutral gray scale and some color blocks. After normal scanning of the standard manuscript, observe a line image in the image in Photoshop 6.0 (observing the white line or black line is particularly obvious) whether the RGB three-channel pixels coincide, so as to check the scanning accuracy (the high magnification should be selected when observing) ). The corresponding pixels of the RGB channels do not coincide, on the one hand it will affect the clarity of the scanned image, on the other hand it will affect the color reproduction effect during the copying process.
Use the neutral gray scale to test the flatbed scanner's ability to restore the neutral gray color and the ability to express the density change of the scale. The correct restoration of the neutral gray color by the scanner is the premise and basis for its color recognition and color restoration. Scanning color shift is caused by the difference between the color sensing performance of the scanning components and the standard components during the scanning process. Although the equipment has been calibrated before the scanner leaves the factory, there are inevitably some color shifts in use. In the actual process, the display screen is often corrected first so that the color can be displayed correctly, and then the scan color cast is corrected.
At present, some pre-press production centers use mid-to-high file scanners, and most of the software can customize output characteristic files. For example, Heidelberg scanning software NewColor can define RGB output characteristic culture. As long as the output characteristic file in the scanning software is set to be consistent with the "RGB setting" in PhotoShop, the image display in PhotoShop and NewColor are almost the same. For scanners with lower file times, it does not support scanning feature files. You can use the functions of PhotoShop.
When correcting the color cast of the scan, put the neutral gray scale after scanning into Photoshop 6.0 image processing software, use the information palette to display the RGB value of each level of the scale in the image, and call Curves curve to adjust the three RGB channels , Until the display value of each step CMYK in the image reaches the required value when neutral gray, and the visual neutral gray scale can be visually observed on the display screen. The Curves curve at this time is the color curve after the scanner corrects the color cast. When scanning the image, the scanned color should be compensated appropriately according to the curve. The curve can be saved for recall. Using the color patches in the standard manuscript to scan, you can determine the scanner's reproduction characteristics for each color. The visual contrast between the original color patch and the scanned image can qualitatively recognize which colors the scanner reproduces better and which colors are worse, so that in the future, the scanned images can be corrected by image processing software for poorly reproducible colors In addition, the scanner should be regularly calibrated.
3. Setting and measurement of printing parameters
It is a very important thing to set the printing parameters. The job that only pays attention to the pre-press production without considering the printing conditions must fail. Only respect the objective conditions of printing, such as the quality of the ink paper, the plate material The resolution, the performance of the printing machine and other factors can make our replica achieve the desired effect. So before copying the manuscript, some printing must be measured. The effective method is to replicate GATF on the stable Heidelberg, Roland, Beiren four-color printing presses through the determined inks and papers, from which we have to obtain: the dot expansion rate, the tristimulus value of CMYK overprinting, suitable Overprint total ink value.
The following is a brief introduction to the GATF color copy test chart, which is divided into six areas according to the map function:  Simple color wheel chart is used to identify colors and detect color reproduction; Contact copy control standard section can be used to detect sun exposure The changes of the dots during the edition process;  dot line number comparison chart, used to select the matching reference of the screen line number and paper suitability, and can also reflect whether the tone reproduction of each color version is normal;  Gray balance card, calculate the ratio of Y, M and C accordingly;  ​​Proofing control bar. Through the printing and copying of the GATF test chart, we can know the transfer of the dots from the film to the PS version, the appropriate number of screen lines, the neutral gray balance and the performance of the machine. This can ensure that from printing to printing, each printing factor has certainty.
Next, in custom CMYK, you can set the ink color, color separation parameters, and dot expansion ratio.
1. Determination of the color of the ink used and the whiteness of the paper
In Photoshop 6.0, use the color setting in the file drop-down menu to enter "Custom CMYK", select the custom in the ink color box, by copying the solid block on the GATF map, the three primary colors are yellow (Y) and product (M) , Cyan (C), three colors red (Y + M = R), green (Y + C = G), blue (M + C = B), synthetic black (Y + M + C), black (K) Eight kinds of color blocks and paper white, use the spectrophotometer to measure the tristimulus value XYZ of each color block and the paper used, and then use the formula x = X / (X + Y + Z) and y = Y / (X + Y + Z) Calculate the brightness coordinates x and y respectively, where Y is the brightness coordinate and the value range is 0 to 100, and the x and y value range is 0 to 1. Then fill this into the box corresponding to "Ink Color".
After filling in the data, the color of each color block in the picture will change. Compare the nine color blocks printed with the color displayed on the screen. If the measurement calculation is correct, the color corresponding will be basically the same. The measurement calculation must be repeated.
Insulated zipper bags maintain food temperature and support the environment all at once! Made from non-woven polypropylene material with an insulated polyester fiber and coated thermal film interior. Keeps food hot or cold for hours! Features square zippered top for a increased capacity. In fact, this is a safe, environmentally friendly, amazing insulated zippered bag that can be reused, stamped with your company's logo, corporate image, and is the perfect project for customer satisfaction and retention strategies. During the shopping process, your customers will proudly carry this bag, thereby exposing your brand and raising awareness of your brand. Of course, you can also choose to offer it for free or have your customers buy it in your store as an alternative to plastic bags.
Thermal Lunch Bag,Thermal Insulated Lunch Bag,Thermal Tote Bag,Take-Away Thermal Bag
Wenzhou Shandao Electronic Commerce Co., Ltd. , https://www.reusablebaglife.com