ADOBE PHOTOSHOP 7 color management
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As is well known, a typical image reproduction system includes multiple input and output devices (scanners, displays, printers, etc.), and each device has its own way of rendering and restoring colors, that is, the color is device dependent. This is why a scanned photo image will appear different colors on the display, on the proof sheet, or on the printed document. In response to this problem, many software developers at home and abroad have invested in the development of color management systems (CMS). The goal is to manage the color of the entire copying process of the image, ensuring that the colors of the same image appear as consistent as possible from input to display and output.
Photoshop is an image processing software developed by Adobe. It is also a complete color management system. Currently, this system is valued by people in the industry for color image processing. In the process of continuous software upgrade, the color management function has also been greatly improved. The color management process of Photoshop7 and how to set the parameters of the software are discussed in detail below.
First, the calibration and characterization of the display
In order for the user to see the color on the screen as close as possible to the color of the output sample, the display must first be calibrated, and any color workflow begins with the calibration and characterization of the display. The purpose of the calibration is to get the best image display environment for editing the image. The purpose of characterization is to obtain the ICC profile of the display, which Photoshop can use to optimize the display of the display.
Users of Windows systems can calibrate and characterize displays by running the Adobe Gamma utility. Users of Mac OS systems can do this through the ColorSync system or the Adobe Gamma utility. Here we mainly discuss the display calibration and characterization of Windows systems.
The Adobe Gamma utility is located in "My Computer → Control Panel". Before running Adobe Gamma, it is best to have the display turned on for more than half an hour to ensure that the screen display is stable, turn off all desktop patterns and set the background color to light gray. To avoid interference with the background color. The operating interface of Adobe Gamma is shown in Figure 1. The specific steps are as follows:
1. Follow the instructions in the introduction and select the "Step by Step (Elves)" method.
2. After clicking the "Load" button, select the profile file of the display or the closest one.
3. Adjust the brightness of the display to its maximum value and adjust the brightness so that the middle frame is as dark as possible and keep the frame bright white.
4. For the “Fluorescent” option, select “Custom” if you have red, green and blue phosphor values for the display given by the manufacturer, otherwise you can select the “Trinitron” or “P22-EBU” type display. .
5. For the setting of the monitor gamma value, first check the single gamma by dragging the slider so that the color of the middle box is as consistent as possible with the surrounding color, and then check the gamma values of red, green and blue, as above. The setting of the Gamma value is 2.2 in Windows and 1.8 in Mac.
6. For the “Hardest Highlights” option, select the white field of the display according to the manufacturer's instructions to determine whether to use warm or cool colors. If there is no manufacturer's instructions, it is best to choose "6500K". Of course, you can also measure the white field of the display by yourself.
7. For the “Best Highlights Adjusted”, it is best to select “As Hardware”.
8. In the final step, click “Finish” to save the monitor's profile file.
Second, Photoshop color settings
Photoshop color settings can be made after the display is calibrated. Go to "Edit → Color Settings" and you will be able to open the Color Settings dialog window. 70% of the color management is done here. Photoshop 7 defaults to the Color Settings window. The dialog window consists of six parts. They are Settings, Workspace, Color Management Scheme, Conversion Options, Advanced Control, and Description. If the "Advanced Mode" checkbox is not activated, there are no "Conversion Options" and "Advanced Control" sections. When the mouse is moved to each section, a brief description of this section is provided in the bottom "Description" section.
1. Settings in the "Settings" section
The default option for “Settings” is “Web Graphics Default Settings”, which can be set differently depending on the purpose of use and the area in which it is located. If you want to simulate the press standard, select "US prepress default setting" or "European prepress default setting" or "Japanese prepress default setting". If you don't want Photoshop to change the color, select "Color management off", but it is best not to choose This item.
2. Settings in the "Workspace" section
First look at the RGB workspace, we should choose "Adobe RGB (1998)" as the working color gamut of the RGB image. The advantage is that the color gamut is moderately sized, which is larger than the color gamut of general CMYK printing. Therefore, when the printed color is displayed on the screen, there is usually no overflow phenomenon, and it has been widely accepted as a standard before printing. "sRGB" is mainly used as the working color gamut of network image design. "ColorMatch" is generally the choice of Mac users, and "AppleRGB" is mainly the choice of network image design in Mac system. These four working color gamuts are device independent. If you want to set the workspace yourself (not listed in the list), you should select the "Custom RGB" option, and then click "OK" after setting the parameters in the pop-up window.
Next is the CMYK workspace. We can select the “Load CMYK” option and select the corresponding ICC Profile file according to the printing process of each image. If users are accustomed to using CMYK settings from previous versions of Photoshop, they can choose the "Photoshop 5 Default CMYK" or "Photoshop 4 Default CMYK" option. If the image is only used for output on inkjet printers such as Epson, HP, etc., the setting of this item is irrelevant because the printer supports RGB color space instead of CMYK color space.
Third, in the gray workspace, we should set the grayscale image accordingly. For example, grayscale images for printing can be set as a percentage of Dot Gain required in the printing process (eg, Dot Gain 10%, Dot Gain 15%, Dot Gain 20%, etc.). The user can also select the "Customize the dot correction" option and set the Dot Gain value as needed.
Fourth, the setting of the spot color workspace is similar to the setting of the gray workspace, and will not be described here.
3. Settings in the "Color Management Plan" section
This part is new in Photoshop 6, and it has not changed in Photoshop 7. Each color space management scheme has the same 3 options. Depending on the purpose of the image output, selecting the "Off", "Keep embedded profile", and "Convert" options in the color management scheme will have completely different effects.
Option "Off" - If the open image does not have a feature file embedded, the image will be edited in the currently defined workspace, and the feature file will not be embedded when the image is stored; if the image embedded feature file matches the current color settings, The image's properties file will be preserved and stored with the image; if the image's embedded property file does not match the current color settings, the original image's properties file will be deleted. This option is equivalent to eliminating color management.
The option "Keep embedded profile" - the processing of an image without an embedded profile is exactly the same as the option "Off"; if the feature file embedded in the image does not match the current color settings, the image is still described in the embedded profile The color is displayed on the display and the current color settings have no effect on this image.
Option "Convert" - If the property file embedded in the image does not match the current color settings, the properties file is converted to the current color settings.
4. Settings in the "Conversion Options" and "Advanced Controls" sections
The "engine" in the "Conversion Options" section asks the user to select a different CMM (Color Management Module), which is generally better than Adobe (ACE). The "intention" can select one of the four options listed (ie, relative colorimetric, absolute colorimetric, perceptible, saturation), and it is better to select "perceptible" in prepress processing. The "Use black field compensation" checkbox should generally not be checked, and the "Use dithering" checkbox can be checked, which will help improve the quality of the dot. The settings in the "Advanced Control" section are as long as the Photoshop default settings are maintained.
Once all the parameters have been set, click "OK" to save the settings.
Third, soft proofing
Soft proofing is to use the display as a proofing device for proofing. In order to achieve accurate soft proofing in Photoshop, some settings are required. It is best to turn off all open images before making settings. This process is done by the "View → Proof Settings → Custom" command. Figure 7 shows the various proofing options.
The meaning of various proofing options are:
Process CMYK, Process Blue, Process Magenta, Process Yellow and Black, and Process CMY—Soft proof the image with the CMYK workspace previously defined in the Color Settings dialog.
Macintosh RGB and Windows RGB—Soft proofs images with standard Mac or Windows monitor profiles.
Display RGB—Soft proofs the image with the monitor's profile.
Simulated Paper White—Lets the user preview the color effect of the white background plus the image in the bottom color based on the current soft proof property file.
Simulated Ink Black—Lets the user preview the color effect of an image within a dynamic range based on the current soft proof property file.
Fourth, manage the color space of the image
In a complete color management process, the conversion of color space is also an essential part. In Photoshop 7, this feature is done via the "Specify Profile" and "Convert to Profile" commands in the Image → Mode menu.
The Specify Profile command allows the user to assign an arbitrary color space profile to the image. For example, many inexpensive scanners do not support scanning profile files, in which case you must use this feature to assign profile files to images. In addition, this feature is also very useful when dealing with photos taken by digital cameras that do not have embedded feature files.
The Convert to Profile command allows the user to convert the color space of the image. For example, when you want to apply the scanning color separation property file to the image, you can use this command, and the image converted by the property file will automatically save the converted property file together when saving.