Color conversion of prepress output images
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The image file used for the print output must be in CMYK color mode, not in RGB mode. The process from RGB mode to CMYK mode, which we call the color separation process. Although this operation is very simple, but really want to make the color separation meet the actual printing conditions, you must pre-set the color separation parameters. The setting of color separation parameters is essentially a part of the color management process. Photoshop combines the setting of color separation parameters into color management after version 5.0.
Start Photoshop software, open the Edit->Color Settings command, and set the CMYK workspace in the workspace settings. You can select the CMYK color space built into Photoshop, or you can set the user according to the actual print output conditions.
Gray space setting
It has a large effect on the value converted from color mode to grayscale mode (GrayScale). For example, for the same RGB color block R75G128B56, when Dot Gain is selected to be 20%, the value K converted to GrayScale mode is 65%; when Dot Gain is 25%, the value K converted to GrayScale mode is 60%; select Dot Gain as At 30%, the value K converted to GrayScale mode is 54%.
Spot color space setting
It directly affects the display color of the spot color image. If Dot Gain is 20%, the spot color with a percentage of 55% is brighter. When Dot Gain is changed to 30%, the color is darker.
Color management solution
Photoshop allows you to embed ICC color profiles in image files in order to manage colors more efficiently through systems and applications. After embedding, the ICC Profile can describe the correct color space for the image file to ensure color consistency. When other applications open the image of the embedded ICC Profile file, if the relevant settings are inconsistent with the embedded, it will automatically judge and decide what to do. In the previous version of Photoshop, the work of embedding the ICC Profile file by "Profile Settings" was changed in Photoshop 7.0, and the ICC Profile was embedded in the storage of image files. If it is an RGB image, the inline is embedded in accordance with the settings of the above RGB space, such as a CMYK image, and is embedded in accordance with the setting of the CMYK space.
When opening an image file in other applications, what happens if ICC Profile does not match the software settings, or if the image does not have an ICC Profile embedded? This is what Color Management Polices wants. solved problem. In the Edit -> Color Settings dialog box, the contents of the color management policies are included. The settings are shown in Figure 6. Here, the RGB, CMYK, and Gray images can be set separately, but the basic content is the same.
Photoshop color space conversion method setting
Open the Edit -> Color Settings dialog box, select "Advanced Mode" at the top of the dialog box, and at the "Conversion Option", you can select the color space conversion. The color management engine (Engine) and the color conversion method (Intent) when performing color space conversion are selected.
Basic settings for Photoshop color management
Open the Edit -> Color Settings dialog and at the top of the dialog there is a "Settings" drop-down menu that determines which color management settings to use. Specific settings include "Color Management Off", "Photoshop 5 Default Color Space", "Web Graphics Default Settings", "US Prepress Default Settings", "European Prepress Default Settings", etc., which operators can use at their discretion. If there are modifications to these settings, it is a custom setting.