Make a characterization file for the scanner (Profiling)
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The scanner is an image digitizing device that is the starting point for most printing jobs. With ICC Profiles, you can get accurate scan files and digital workflows that deliver precise color delivery. Scanning is the most important part of the digital workflow. If you don't have problems in the downstream process, you must pay special attention to the scanning process. Making a scanner's profile is relatively straightforward because the scanner is a relatively easy to control device. For flatbed scanners, you only need to close the scanner's lid and fix the light source and imaging size to get a high-quality characterization file. Here's a quick overview of how to make and use the scanner's characterization file, how to set up the scanner, and how to choose a scanner test swatch.
Scanner feature file summary
There are usually two steps to color management a scanner. First, create a characterization file for the scanner; then apply a characterization file when scanning the image. Each scanned image must be associated with a profile. There are many ways to apply a profile, such as embedding it into an image, which can be applied directly to the image via the scanning software, or Combine images and characterization files (as in Photoshop). It doesn't matter which method you use to combine the image with the characterization file. It is important to link the characterization file to the image or to associate it.
The characterization file can improve the quality of scanned images, widen the contrast of images, enhance the reproduction of image tones, and better replicate colors. But this also means that the scanner profile can correct poor originals, it can only copy the original accurately. Therefore, if the contrast of the original is very low and the color is not very vivid, then the characteristic file of the input device can only guarantee accurate copying of the original, and it is impossible to improve the quality of the image itself.
Select test swatch
In order to generate the characterization file of the scanner, a test swatch needs to be selected. The principle of selecting the swatch is based on the type of material to be scanned. If the transmission is to be scanned, the transmission test swatch needs to be selected. The standard transmission test swatch is an IT8.7/1 swatch. If the original to be scanned is a printed original, you need to select the IT8.7/2 swatch. IT8.7/1 and IT8.7/2 are identical in appearance but are made of different materials. Fuji, Agfa, and Monaco's IT8 contain 288 color blocks, while Kodak's IT8 has 252 color blocks (there is a portrait of a character on the right side of the swatch).
The software that makes the profile also supports some special test swatches, such as the HutchColor color scale, which is a relatively new swatch that contains different number of patches and different color choices. In addition, negative swatches are available from manufacturers, and Fujifilm ColourKit is one of the few manufacturers to provide negative characterization documents. Fujifilm's software can scan negative images with color negative swatches.
The principle of selecting a swatch is that it can represent the material to be scanned, such as scanning the transmission draft and selecting the transmission swatch. If it is further possible to unify the type of scanning material and the type of swatch material, that is, two materials. The type of pigment composition used is consistent. If you are scanning a Fujicolor original, the scanner's characterization file is best generated by the Fujicolor IT8.7/2 swatch. This is because the characterization file is a reflection of the overall situation of the system, that is, it measures not only the scanner itself, but also a mixture of both the scanner and the film.
Similarly, if you are scanning an Ektacolor manuscript, you should use the Ektacolor IT8.7/2 swatch to create a characterization file. Usually, a series of products uses only a limited number of pigments, so an Ektacolor swatch can be applied to a variety of Ektacolor papers; Ektacolor transmission swatches can also be applied to a variety of Ektacolor series of films. If this match cannot be fully implemented, then at least Kodak must be guaranteed for Kodak, Fuji for Fuji, and so on.
Scan test swatch
In order to generate a characterization file for an input device, first turn off all scanner interface controls and then scan the test swatches. It is very important to turn off the automatic control of all correction tones and color reproduction. Some systems are usually set to automatic color balance, and the colors in the image are automatically corrected according to the image. Do not initiate any automatic color control when generating the characterization file for an input device, and do not want the scanning software to use the "smart" feature. Because we want to be able to record and study the full behavior of the device, we are more interested in the original response to the device. The application of any image control tool has the potential to reduce the color rendering range of the scanner to some extent. In addition, you need to pay attention to whether the sharpening control function is turned off. When scanning the swatch, you cannot perform the sharpening setting, and set all the sharpening mask parameters to zero.
In addition, there is an extra caution when scanning the test swatches, especially when scanning the transmission test swatches. If the transmission swatch is placed on the platform without any occlusion around it, the light will be reflected back, causing irregular shadows to appear. The scanning resolution should be chosen appropriately. If the swatch size is too small, the number of pixels per color block on the swatch will not be enough to generate enough data. If the size of the swatch is large, the software that makes the characterization file may not work properly. The normal scan resolution is set to 300 dpi, and the resulting image file is manageable and can be accepted by most software packages that make feature files. Other experiences are to clean the scanning platform, remove the fingerprints and smudges on the table, and position the swatches (horizontal and vertical), taking care to include the registration marks on the swatches. Save the scanned file as an uncompressed image file.
Reference document
Before you can make a characterization file for your device, you need a file -- a reference file. The reference file is provided by the manufacturer of the test swatch, which contains the LAB/XYZ values for each color patch standard on the swatch provided by the manufacturer. The reference file is a simple text file that can be opened by any word processing software. Software such as Microsoft Word or Notepad. Note that the data for the HutchColor swatches are measured separately, while the data for the IT8 swatches is measured in batches. Some manufacturers include reference files in the production characterization software provided, and some downloads of reference files on the website, such as ftp.kodak.com/gastds/Q60DATA
Software for making characterization files
Once you have prepared the scanned swatches and reference files, you are ready to create the characterization files. Start the software package that makes the characterization file, and then rely on the operation wizard provided by the software to determine the location of the scanned swatch image and reference file. After determining the location, the software will automatically generate the characterization file of the scanner.
The generated characterization file is saved in a location in the system software and is automatically done by the software. Only the characterization files are saved in the correct location, and the application software (such as Photoshop or Indesign) can find and use these files. Each operating system reserves a specified location for the profile. In the Mac OS X operating system, there are several places to save the profile, one of which is Library/ColorSync/Profiles. This makes the characterization file available and can be applied when scanning the image.
Quality of the scanner's characterization
After the characterization file is created, it must be checked before it can be applied. The inspection should be based on both subjective (visual) and objective. At this point we don't have to worry about whether the scanner itself is good or bad. You don't need to know if the scanner is worth $100 or $1,000. What we need to check is whether the characterization file can completely "map" the scanner's behavior. It is normal for a low-grade scanner to have a high-quality characterization file. That is, although the quality of the scanner itself is poor, if it has a high-quality characterization file, it can accurately express it. Every behavior of the device, such a profile is a very useful file for color management.
Many manufacturers make tracking feedback on the generated profile, which is represented by △E. △E may represent the color tolerance of each color block, or it may be the color difference of all color blocks on the entire color plate. If the average or maximum ΔE is high, it is recommended to re-examine the process of making the characterization file and re-create it. The average color difference of the scanner profile should be less than 5 ΔE, preferably between 1-2 ΔE. If there is a large error, carefully check the entire manufacturing process. There are many reasons why the quality is usually not high. The scanner or test swatch is not clean, the swatch is not placed properly (not correct), or the reference file is incorrect. The software that makes the characterization file may also have problems, or the device itself may not work properly and is not suitable for making characterization files.
In conclusion
The scanning of images is the starting point of the printing workflow. The quality of this process is directly related to the quality of the entire workflow. Making a scanner's characterization file is a very simple matter, and many software that produces characterization files can now produce high-quality scanner characterization files. Some users will use the steps described above to create a characterization file for their device. If you do not have this capability, consider using the intrinsic characterization files provided by the device vendor. If the above two methods do not work, then you can choose a feature file to apply. At this time, you may choose the display's characterization file, a color space characterization file (such as sRGB) or the characteristics of the Photoshop workspace. Description file. In the color management workflow, each image must be marked, which means that each image must have a characterization file, so if you can't get a suitable input characterization file for your device, then you have to do it. The way to get one, this is a very important color management step.