The latest trends in scanners
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At present, the printing industry is facing increasingly fierce competition. In order to increase the weight in the competition, various printing companies are increasing their investment in printing equipment, especially for new prepress equipment. Because customers have higher and higher requirements for the quality of printed products, the quality of prepress data processing determines the quality of printed products to a large extent. In fact, the quality of printed products is not only achieved by hardware, but by the combination of software. This article explains how to achieve the best reproduction of images and the direction of future development from the perspective of hardware and software.
1. Progress in scanning technology
The current scanning technology uses the RGB color filter to decompose the color into blue (C), magenta (M), and yellow (Y) signals, and then uses the CMYK color correction device to determine the color characteristics (color, density) of the original. The mixing state of the color filter of the color filter and the color characteristics of the printed color (the color of the CMY ink) are controlled.
Since these data settings require the operator to look at the original document and determine it by experience, the operator's data will be different depending on the operator, resulting in a difference in color reproduction. This tells us that to ensure the faithful reproduction of the original or the quality of the color separation required by the customer, experienced and excellent operators are the key to success.
In addition, when the printing conditions (paper, ink, etc.) are changed and a new scanning device is introduced, the color correction setting needs to be performed again, and it is necessary to repeatedly test by the operator's experience and judgment to reduce the error.
The latest CMYK scanners have already stored the repair settings set by the manufacturer, and this value is expressed in the form of data. Thanks to the automatic setting function and auxiliary function that match the original setting, even an operator without scanning experience can easily input images and obtain high-quality scanned documents.
However, it can be said that even now, with such a scanner based on the CMYK color corrector, it is difficult to achieve similar color reproduction.
2. Changes brought about by the emergence of color management
Since Heidelberg provided color management technology to Apple's ColorSync 2.0 and Microsoft's ICM 2.0, the understanding of scanner color correction has gradually changed.
In the new color management method, it is only necessary to convert the scanner signal to the CIELab space at one time (the color space that can indicate the color reproduction characteristics without being affected by specific conditions such as printing conditions and printers), and it is free from printing ink, Devices such as monitors affect the acquisition of image data; when outputting data, color conversion is automatically performed in the color space of the device to automatically produce the data required for color matching.
Since CYMK is compatible with specific color reproduction characteristics (color space) such as paper and ink, although the colors reproduced in the other color space devices (proofing machine, etc.) after inputting data may differ, it is still possible to pass CIELab. Space expresses color in absolute form, which is a big advantage.
In addition, since the entire visible light region can be represented, it can be converted into CMYK for printing, and can also be converted into data for various RGB devices, that is, color conversion can be performed on a device having any color space. That is to say, by simply creating the required ICC data map, it can be easily converted to CMYK data that meets various printing conditions.
Moreover, since the CMYK data is formulated by the ICC data map, whether the hardware and software conform to the ICC data chart standard has a great influence on the quality of the printed matter. Heidelberg's Print
Open ICC is a software that meets the above criteria.
■Edit the function of the data graph
What needs to be noted here is the difference in the color space between the color film original and the printed matter. In the original, even if color matching is performed separately, some colors and concentrations cannot be reproduced in printing. Print The Open ICC software uses Heidelberg's patented color-color scanner color reproduction technology, which reproduces the color space.
Of course, the user can also change the settings. One is to reproduce the darkness of the part or emphasize the vividness of the color by reproducing the contrast curve of the color. There is also a saturation control function that highlights the saturation of the color or the level of the color.
In addition, you can set the background color removal, gray removal (this function is to replace the turbid color such as dark red instead of the blue version instead of the blue version, to suppress the turbidity of the color), etc. These functions determine the characteristics of the ICC data map.
■ICC data chart and color adjustment
Indeed, the use of ICC data maps makes it easy to efficiently color match color originals that match the printing conditions and color space, but for the scanner operator and the prepress department, this alone does not faithfully reproduce the colors that meet the company's requirements. .
To date, there is another feature in the color adjustment of the scanner. That is, no matter what color the original is, it is necessary to color the color called the memory color (such as the sky, the color of the sea, the green color of the lawn, and the color of the human skin). In other words, you must adjust the color and gray balance that does not meet customer requirements.
These and color matching are obviously different jobs. In general, it should not be entered into the ICC data plot. Even if the quality of the ICC data map is not good enough, it is possible to produce better quality color decomposition data by inputting the color correction value to the ICC data map in advance.
Heidelberg scanner driver software Linocolor (for Apple), Newcolor 7000 (For PC computers, it is possible to input the color adjustment and color trimming values of the scanner into the ICC data map.
3. New generation scanning software New color 7000
Heidelberg's newly developed scanning software is New color 7000, which is the same as Linocolor, anyone can perform LCH adjustments to trim colors. In addition, there is the most advanced scanner Chroma Graph The S3900 has CMYK trimming, color grading, and background removal. Therefore, even professional operators only need to use CMYK values to freely control the nuances of various colors. In addition, the color of the software is based on CIELab space and ICC data map, which is the biggest difference between it and traditional scanning software. Therefore, there is no need to use a gray scale to create a color gradation curve, and there is no need to perform color correction and original color matching. It is only necessary to set the scanner ICC data map required for Kodak, Fuji, Agfa color film and ICC data in accordance with printing conditions. The picture can be color matched.
When paper, ink, printing press, etc. are changed, it is necessary to print the color table required to make the ICC data map in advance, and only need to make PrintOpen with ICC software.
The ICC data map allows for easy color matching in any printing condition. Then, simply recall the color trim data file that the company needs to reproduce the most appropriate color.
Another feature is its new scanning workflow, which means that the settings and trimming of each original can be separated from the scanning. Since there is no special requirement for the operator during scanning, anyone can focus on continuously inputting a large number of images and continuously scan them, which greatly increases productivity.
In this workflow, a working platform for Newcolor is required, so the operator can check the quality and trim the color efficiently. Use Newcolor 7000, image data can be saved in 16-bit input. Since the 256 layers of 8-bit data have a total of 65,536 levels, it is not only the color trimming, but also the level of highlights and shadows, and it can perfectly reproduce images without quality loss.
4. Changes in image acquisition technology
Recently, charge coupled devices (CCDs) have been mainly used in image acquisition technology. This is not only because the quality of the charge-coupled component is getting better and better, but also because it can be produced at a large amount of low cost; and the main structure of the scanner is simple, which reduces the total investment cost.
However, if the quality requirements are high, a roller scanner is required. The difference in scanning quality is explained below by comparing the structure of the flatbed scanner and the drum scanner.
Structural comparison of drum type and flat table scanner
The fundamental difference between the two is that charge-coupled components are used in the light-receiving components of flatbed scanners, while photo-multipliers are used in drum scanners. The disadvantage of the charge-coupled element is that it is difficult to reproduce the range of the color density due to the large interference of the dark-adjusted portion, but in expensive high-end scanners, various techniques are being used to reduce the interference of the dark-tone portion. Since the flatbed scanner uses the fluorescent tube as the light source, the portion other than the original can also be irradiated, so that the refraction of the light reduces the contrast of the dark portion and does not reproduce the layer well. It is usually surrounded by a black frame around the original to prevent this from happening. However, there is also a strong contrast in the center of the original, and there is no way to prevent it.
Heidelberg's latest platform scanner, the Nexscan F4000 series, is completely free of light reaching the reflective surface of the charge-coupled component, preventing unwanted light from interfering.
Since the drum scanner can scan with dots and the light source is also a point, it is not affected by unwanted light. In addition, when the charge-coupled element is used for high-magnification scanning, each element of the charge-coupled element reads an image in a unit smaller than the actual one pixel, so the original is read one by one.
Once the sharpness is adjusted, the scanning effect will be greatly improved.
On the other hand, since the aperture stop of the drum scanner can freely change the dot size of the read optical image, it can be read with a slightly larger pixel. Therefore, especially in the case where the granularity of the original is not good, the color can be stably reproduced by reading a plurality of particles at a time to make the concentration and color uniform.
In general, the difference in optical precision is large. The charge-coupled element reaches about 5000 dpi, while the drum type reaches 10,000 dpi or more. There is a difference in quality between the two. It can be said that the quality of the charge-coupled element is the size of the charge-coupled element itself.
Of course, the difference in resolution between the charge-coupled components and the drum scanner will be smaller and smaller. Heidelberg has also developed a series of vertical Scanscan roller scanners, which reduces costs, and its space setting and platform type. The scanners are the same so that they can be put together.
5. Digital camera image acquisition technology
Charge-coupled component digital cameras are divided into two types: one-piece type and black-box type. The cameras used in printing are mostly black-box type. It is characterized by loading 6×6cm, 6×7cm, 4×5 An inch of film makes it easy to connect the camera's black box with a connector.
Heidelberg also introduced a black box-type Colorcam charge-coupled component digital camera for the printing industry. At the same time, a multi-shot model with the latest technology will be introduced.
Since the shutter speed of a single-shot camera is 30 seconds to 1/1000 seconds, it is suitable for shooting by people. The multi-shot type is divided into three models: one shot, four shots, and 16 shots. Except for one shot type, the rest are used for still life shooting.
In a one-shot type camera, the charge-coupled elements are slightly rotated before the shutter is pressed, and each charge-coupled element can read the image portion of the side-by-side component. Thus, the number of pixels read is increased to prevent the moiré peculiar to the charge coupled device.
The 4-shot camera has a position in which the adjacent charge-coupled elements are shifted by one position each time, and as a result, the number of color pixels of the charge-coupled element is increased to reproduce higher-quality colors and subtle levels.
When shooting with a 16-camera camera, the charge-coupled components are staggered to halve the width, so that the optical resolution can be increased by a factor of four, ie: 6144 × 4096 Pixel to take an image. Therefore, it is also possible to shoot A1 to B1 size posters, which is a breakthrough for digital cameras. And the advantage of digital cameras is that the plate making time is short and saves a lot of time.
Of course, color management is required to achieve this. Use Colorcam's proprietary software, Linocolor Cam, you can make an ICC data chart by simply shooting a color chart, and you can use the ICC data chart for printing to output CMYK data.
6. Image acquisition technology outlook
Color management based on ICC data maps will undoubtedly be used for all devices. From the application used to process this data as well as PostScript The characteristics of RIP can be seen, when and where color management will become a key issue in the entire workflow, that is, whether the data is input in RGB or pre-entered into a secure CIELab space, or Use CMYK data for printing purposes? Is 8bit or 16bit selected? Should I adjust the clarity in advance? ......
Because of these options, users should consider how to save image data and how to develop a database in the future. It can also be said that the period of rethinking the workflow has arrived.