In prepress technology, capturing images is very important. There are several options for its configuration and the equipment that best suits the job must be carefully selected.
Scanners Today, you can find a wide variety of color scanners, from manual scanners, flatbed scanners, to transmission scanners and roller scanners. Each has a special purpose in the image capture process. Before using the device, it is necessary to analyze the type of original to be processed and the end use of the captured image. Some scanners in use today are middle and low-end desktop platform scanners that collect light reflected from printed manuscripts or line drawings. Most prepress service providers and printers should purchase high-end scanners that provide the quality and speed that low-end scanners cannot provide. Important factors to consider when selecting a scanner are dynamic range, resolution, image size, scanning software, and the ability to scan transmissive materials.
If you are going to do a lot of color scanning, you should be able to provide more than megabytes of storage space for the scanned image and store it at an amazing speed. In addition, color scanning can take up a lot of computer storage space and reduce the display refresh rate. Configure your computer according to its maximum amount of storage. Also check the low-resolution switching performance of OPI/APR, and the compatibility of the files discussed in the page output section and technical support.
The introduction of the collection of digital images of digital camera and camera black-boxes may be the most important development since the appearance of color films 60 years ago. Digital cameras and camera darkboxes, which are currently widely used in consumer and commercial applications (especially for product catalogs), have allowed camera users to create pre-separated digital images for electronic processing. Digital technology also allows photographers the flexibility to instantly preview image lattices and choose to delete or save data points. The decision to take a sheet can be made by comparison after several hours or days after image capture. The market for digital cameras is growing very fast. With the improvement of quality and lower prices, the trend of digitalization is increasing with the promotion of amateur and professional photographers.
As an image capture and color separation device, digital cameras have made the boundaries between conventional image reproduction paths—from the photographer to the film to the extension to the image processor—not clear. Digital cameras force photographers to understand how color separations have been widely used for many years—the tone control of color separations is a basic requirement for high quality reproduction.
All digital cameras have a display for viewing the collection point, a video output port, and a slot for a removable and reusable memory card or disk for storing electronic images. Professional digital cameras provide the highest resolution, exposure and focus control. Some professional digital cameras have an over-the-lens optical viewfinder, similar to a single-lens reflex camera, which allows the user to observe while shooting (for most digital and film cameras, viewfinders and optical lenses It is separate.)
Digital cameras replace film with solid, light-sensitive silicon. The image is recorded using a CCD. The CCD chip is made of a tiny light-sensitive element or unit, which acquires a charge proportionally to the light intensity (generation of electrons). The light sensitive unit of the CCD chip digitizes light by converting light into magnetic pulses. Digital images are recorded on the camera's memory card or disk, or transferred to the workstation's host via a serial interface. Digital images are recorded in RGB values.
Digital cameras have two basic CCD arrangements, called layouts: linear or area. In a linear layout, individual cells are arranged in a single line or in three rows (three lines, each row corresponds to one of the RGB colors). The linear arrangement moves along the image area and records RGB with three channels, or, in a three-line arrangement, all three colors are in one channel. In a face scan, the cells are rectangularly arranged in all RGB values ​​sufficient to capture the image in one exposure. Another arrangement contains three filter wheels that can rotate to record the same RGB value in three exposures.
The criterion for evaluating the image quality of a digital camera is the maximum resolution and color depth of the pixel. The resolution defines how many pixels a CCD can capture, and the bit depth defines the amount of color bits for a pixel. Digital cameras can reproduce color and more midtones. If this is puzzling, consider the computer as a binary system to store all data in a series of 1s and 0s. If only one pixel is used to describe a pixel, then the pixel is either white or black - there is not enough information to show the midtone gray. However, if you describe a pixel with a longer column of bytes, you can perceive a gray gradient. The 8-bit byte can provide 256 possible combinations of 0 and 1. Therefore, a bit depth of 8 can provide 256 tone values ​​or grayscale variations. The slight increase in bit depth is a geometric multiple of the tone information. For example, if the bit depth is 12, there are 4096 gray levels, and when the bit depth is 14, the gray level is increased to 16384.
Other factors to consider are image acquisition time and file storage. With image capture, digital cameras take longer than traditional film cameras. Because the CCD array of a digital camera is used repeatedly for each acquisition point, the image data must be stored in memory before the next point is acquired. File storage can affect the speed with which a digital camera stores images on the memory card or on the computer's hard disk. However, once the image is captured in RGB data format, there is no need for a series of processes such as film processing, scanning and color separation. With the development of digital color proofing and digital platemaking, digital photography has brought us closer and closer to the true digital workflow.
Not long ago, photocopiers were mainly used as a simple way for large companies to copy color materials. When the color copying machine can be connected to a computer like a platform scanner, it begins to be widely used. With the ability of color copiers to have fast and powerful RIPs, copiers have evolved into short-run, digital color presses. Today, the service department, express printing companies, and creation departments often use color copiers in a networked environment, just like the production of low-cost, short-run, variable-data digital color printing.
Color Management System The Color Management System (CMS) adjusts the colors between monitors, scanners, scanning software, digital proofing devices, image recording media (films or plates), contract proofs, and final printed proofs. CSM can ensure the stability of the color reproduction process by correcting the color difference produced by different devices.
File format Consult the prepress service provider and which file format can be used. Also refer to the Technical Manual for more information on the criteria for document compliance.
Once the storage device has captured the image, it needs to be stored for use in later designs. If you make your own images, the easiest way to store images is to store the images on your hard drive. However, if you need to send images to a prepress service provider, you need a removable storage device. Optional removable storage devices are: floppy disks - tapes; removable hard disks - permanent magnetic; optical disks - CD-ROMs, DVDs (digital video disks).
How can an image be converted from RGB format to CM YK format?
Although you can choose to acquire images in the RGB format, they must be converted to CM YK format before the final film output or plate imaging. Some service providers prefer to convert RGB to CM YK on their own prepress systems. However, if the image is converted on the desktop from RGB to CM YK format by itself during the scan or by using image editing software, be sure to consult the printing service provider for the values ​​required for proper conversion.
Is the scan resolution appropriate?
When scanning an image, a higher setting per pixel (ppi) is not a requirement to improve the final output quality. However, higher ppi readings do require more storage space. For a job to be printed, the best results are obtained if it can be scanned with twice the number of lpi (line per inch) that it ultimately outputs as the scanned pp i number.
This relationship ensures that enough color information can be captured to accurately produce halftone images. To get the best image at the lowest cost in terms of file size and output processing time, plan page and image size before scanning.
For example, if you plan to resample an image for another purpose, you need to double the normal input ppi according to the percentage of magnification. For example: An image output resolution that is to be printed at 133 lpi and enlarged by 150% of the job should have a resolution of 133 x 2 x 1.5 = 399 pp i. Zooming out is easier than zooming in. When the image is zoomed out, pixels are usually lost; but when the image is zoomed in, the true image pixels cannot be increased to maintain resolution. At the same time, to avoid ladders, fonts and line drawings are higher than the input resolution of continuously adjusted photo images.
Correct understanding of ppi, lpi, dpi and why care about these?
Both ppi, lpi, and dpi describe an confusing three-word abbreviation used throughout the industry. Defined as follows, each of the methods used in the capture and printing of images cites a unique, independent step of measurement: ppi, or pixels per inch, is a measure of the amount of information scanned for a sample or image. The better the optical performance of the scanner, the higher the scanning resolution, which is the critical value of the image quality.
Lpi, also known as the number of lines per inch or screen line, is the measure of the frequency of the halftone screen used during subsequent image printing. The specific lpi is selected depending on the weight of the paper. To take a step back, the lpi value you consult with the printer will determine how much ppi to use during the early image scanning process.
Dpi, or dot per inch, is a measure of the resolution of output devices such as laser printers, copiers, digital proofing devices, laser imagesetters, and platesetters.
For example: You may need to scan the transmitted document at a resolution of 300ppi because the image is printed on the paper at a resolution of 150lpi and you have to preview it on the monitor at a resolution of 75dpi.
The two-color overprint method is to reduce the printing problem and use the default value of the number of screen lines and the angle of the network line to save the two-color version. The color either uses CM YK four colors or uses spot colors instead of RBG colors. To avoid unnecessary film output and related costs, ensure that the colors are correct and consistent in design and image editing.
Is your image size correct?
During the editing of the scan and the image, it is necessary to cut the image and make it fit. If you wait until the image is cut in the page design program, the cut part will remain part of your file and create an unnecessarily large, unmanageable file. If you resize the image in the page design file, this feature should be considered every time the document is printed. This can greatly increase processing time and can lead to printing errors.
Does your image need to be changed?
As a general rule, images are always edited in the image editing software (for example: resizing, cropping, rotating, flipping, compositing) before adding the image to the page editing file. For example, rotating or flipping an image during a scan can save the page design program from considering rotation at every print. This consideration is very time-saving and memory-intensive.
Whether you need to compress a file to compress the image file will affect the quality of the processing and printing proofs. Usually, some prepress service providers do not recommend compressing image files. Before you provide the image files compressed by the prepress service provider, be sure to check with them.
Ø Copy quality: You need high-density and sharp lenses.
Ø Scanning Resolution: Continuously tuned images may only require 300 dpi resolution, while pictorial, graphic, and fonts require at least 600 dpi.
Factors to consider:
If the RGB image is converted to the CMYK format without considering the paper, printer, or ink used, the final print quality of the image will not be as expected.
Image files
Scanners Today, you can find a wide variety of color scanners, from manual scanners, flatbed scanners, to transmission scanners and roller scanners. Each has a special purpose in the image capture process. Before using the device, it is necessary to analyze the type of original to be processed and the end use of the captured image. Some scanners in use today are middle and low-end desktop platform scanners that collect light reflected from printed manuscripts or line drawings. Most prepress service providers and printers should purchase high-end scanners that provide the quality and speed that low-end scanners cannot provide. Important factors to consider when selecting a scanner are dynamic range, resolution, image size, scanning software, and the ability to scan transmissive materials.
If you are going to do a lot of color scanning, you should be able to provide more than megabytes of storage space for the scanned image and store it at an amazing speed. In addition, color scanning can take up a lot of computer storage space and reduce the display refresh rate. Configure your computer according to its maximum amount of storage. Also check the low-resolution switching performance of OPI/APR, and the compatibility of the files discussed in the page output section and technical support.
The introduction of the collection of digital images of digital camera and camera black-boxes may be the most important development since the appearance of color films 60 years ago. Digital cameras and camera darkboxes, which are currently widely used in consumer and commercial applications (especially for product catalogs), have allowed camera users to create pre-separated digital images for electronic processing. Digital technology also allows photographers the flexibility to instantly preview image lattices and choose to delete or save data points. The decision to take a sheet can be made by comparison after several hours or days after image capture. The market for digital cameras is growing very fast. With the improvement of quality and lower prices, the trend of digitalization is increasing with the promotion of amateur and professional photographers.
As an image capture and color separation device, digital cameras have made the boundaries between conventional image reproduction paths—from the photographer to the film to the extension to the image processor—not clear. Digital cameras force photographers to understand how color separations have been widely used for many years—the tone control of color separations is a basic requirement for high quality reproduction.
All digital cameras have a display for viewing the collection point, a video output port, and a slot for a removable and reusable memory card or disk for storing electronic images. Professional digital cameras provide the highest resolution, exposure and focus control. Some professional digital cameras have an over-the-lens optical viewfinder, similar to a single-lens reflex camera, which allows the user to observe while shooting (for most digital and film cameras, viewfinders and optical lenses It is separate.)
Digital cameras replace film with solid, light-sensitive silicon. The image is recorded using a CCD. The CCD chip is made of a tiny light-sensitive element or unit, which acquires a charge proportionally to the light intensity (generation of electrons). The light sensitive unit of the CCD chip digitizes light by converting light into magnetic pulses. Digital images are recorded on the camera's memory card or disk, or transferred to the workstation's host via a serial interface. Digital images are recorded in RGB values.
Digital cameras have two basic CCD arrangements, called layouts: linear or area. In a linear layout, individual cells are arranged in a single line or in three rows (three lines, each row corresponds to one of the RGB colors). The linear arrangement moves along the image area and records RGB with three channels, or, in a three-line arrangement, all three colors are in one channel. In a face scan, the cells are rectangularly arranged in all RGB values ​​sufficient to capture the image in one exposure. Another arrangement contains three filter wheels that can rotate to record the same RGB value in three exposures.
The criterion for evaluating the image quality of a digital camera is the maximum resolution and color depth of the pixel. The resolution defines how many pixels a CCD can capture, and the bit depth defines the amount of color bits for a pixel. Digital cameras can reproduce color and more midtones. If this is puzzling, consider the computer as a binary system to store all data in a series of 1s and 0s. If only one pixel is used to describe a pixel, then the pixel is either white or black - there is not enough information to show the midtone gray. However, if you describe a pixel with a longer column of bytes, you can perceive a gray gradient. The 8-bit byte can provide 256 possible combinations of 0 and 1. Therefore, a bit depth of 8 can provide 256 tone values ​​or grayscale variations. The slight increase in bit depth is a geometric multiple of the tone information. For example, if the bit depth is 12, there are 4096 gray levels, and when the bit depth is 14, the gray level is increased to 16384.
Other factors to consider are image acquisition time and file storage. With image capture, digital cameras take longer than traditional film cameras. Because the CCD array of a digital camera is used repeatedly for each acquisition point, the image data must be stored in memory before the next point is acquired. File storage can affect the speed with which a digital camera stores images on the memory card or on the computer's hard disk. However, once the image is captured in RGB data format, there is no need for a series of processes such as film processing, scanning and color separation. With the development of digital color proofing and digital platemaking, digital photography has brought us closer and closer to the true digital workflow.
Not long ago, photocopiers were mainly used as a simple way for large companies to copy color materials. When the color copying machine can be connected to a computer like a platform scanner, it begins to be widely used. With the ability of color copiers to have fast and powerful RIPs, copiers have evolved into short-run, digital color presses. Today, the service department, express printing companies, and creation departments often use color copiers in a networked environment, just like the production of low-cost, short-run, variable-data digital color printing.
Color Management System The Color Management System (CMS) adjusts the colors between monitors, scanners, scanning software, digital proofing devices, image recording media (films or plates), contract proofs, and final printed proofs. CSM can ensure the stability of the color reproduction process by correcting the color difference produced by different devices.
File format Consult the prepress service provider and which file format can be used. Also refer to the Technical Manual for more information on the criteria for document compliance.
Once the storage device has captured the image, it needs to be stored for use in later designs. If you make your own images, the easiest way to store images is to store the images on your hard drive. However, if you need to send images to a prepress service provider, you need a removable storage device. Optional removable storage devices are: floppy disks - tapes; removable hard disks - permanent magnetic; optical disks - CD-ROMs, DVDs (digital video disks).
How can an image be converted from RGB format to CM YK format?
Although you can choose to acquire images in the RGB format, they must be converted to CM YK format before the final film output or plate imaging. Some service providers prefer to convert RGB to CM YK on their own prepress systems. However, if the image is converted on the desktop from RGB to CM YK format by itself during the scan or by using image editing software, be sure to consult the printing service provider for the values ​​required for proper conversion.
Is the scan resolution appropriate?
When scanning an image, a higher setting per pixel (ppi) is not a requirement to improve the final output quality. However, higher ppi readings do require more storage space. For a job to be printed, the best results are obtained if it can be scanned with twice the number of lpi (line per inch) that it ultimately outputs as the scanned pp i number.
This relationship ensures that enough color information can be captured to accurately produce halftone images. To get the best image at the lowest cost in terms of file size and output processing time, plan page and image size before scanning.
For example, if you plan to resample an image for another purpose, you need to double the normal input ppi according to the percentage of magnification. For example: An image output resolution that is to be printed at 133 lpi and enlarged by 150% of the job should have a resolution of 133 x 2 x 1.5 = 399 pp i. Zooming out is easier than zooming in. When the image is zoomed out, pixels are usually lost; but when the image is zoomed in, the true image pixels cannot be increased to maintain resolution. At the same time, to avoid ladders, fonts and line drawings are higher than the input resolution of continuously adjusted photo images.
Correct understanding of ppi, lpi, dpi and why care about these?
Both ppi, lpi, and dpi describe an confusing three-word abbreviation used throughout the industry. Defined as follows, each of the methods used in the capture and printing of images cites a unique, independent step of measurement: ppi, or pixels per inch, is a measure of the amount of information scanned for a sample or image. The better the optical performance of the scanner, the higher the scanning resolution, which is the critical value of the image quality.
Lpi, also known as the number of lines per inch or screen line, is the measure of the frequency of the halftone screen used during subsequent image printing. The specific lpi is selected depending on the weight of the paper. To take a step back, the lpi value you consult with the printer will determine how much ppi to use during the early image scanning process.
Dpi, or dot per inch, is a measure of the resolution of output devices such as laser printers, copiers, digital proofing devices, laser imagesetters, and platesetters.
For example: You may need to scan the transmitted document at a resolution of 300ppi because the image is printed on the paper at a resolution of 150lpi and you have to preview it on the monitor at a resolution of 75dpi.
The two-color overprint method is to reduce the printing problem and use the default value of the number of screen lines and the angle of the network line to save the two-color version. The color either uses CM YK four colors or uses spot colors instead of RBG colors. To avoid unnecessary film output and related costs, ensure that the colors are correct and consistent in design and image editing.
Is your image size correct?
During the editing of the scan and the image, it is necessary to cut the image and make it fit. If you wait until the image is cut in the page design program, the cut part will remain part of your file and create an unnecessarily large, unmanageable file. If you resize the image in the page design file, this feature should be considered every time the document is printed. This can greatly increase processing time and can lead to printing errors.
Does your image need to be changed?
As a general rule, images are always edited in the image editing software (for example: resizing, cropping, rotating, flipping, compositing) before adding the image to the page editing file. For example, rotating or flipping an image during a scan can save the page design program from considering rotation at every print. This consideration is very time-saving and memory-intensive.
Whether you need to compress a file to compress the image file will affect the quality of the processing and printing proofs. Usually, some prepress service providers do not recommend compressing image files. Before you provide the image files compressed by the prepress service provider, be sure to check with them.
Ø Copy quality: You need high-density and sharp lenses.
Ø Scanning Resolution: Continuously tuned images may only require 300 dpi resolution, while pictorial, graphic, and fonts require at least 600 dpi.
Factors to consider:
If the RGB image is converted to the CMYK format without considering the paper, printer, or ink used, the final print quality of the image will not be as expected.
Image files
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