Looking at PS Color Management from Frequently Occurred Problems in Prepress Enterprises (I)

Color management is a very complex concept, and many staff in the prepress area still have problems setting the right options and operations in Photoshop software so that they sometimes have serious consequences in printing. This article briefly describes the classification of some issues that are often encountered in prepress businesses, with a view to providing readers with inspiration and help.

1. Overview settings and color management solutions

If an image file does not have or has an incorrect ICC profile (Profile, Profile in Photoshop 5.X, Color Profile in 6.X, Same Meaning), what should be done? In Photoshop 5. Settings can be set in the “Profile” menu in X: 1) If the image file is not embedded in the ICC profile, an assumed profile can be specified and then converted automatically; 2) If the profile of the image does not match the current color settings , you can choose "Ignore", "Conversion" and "Open the question" three options.

Whether to save the image file needs to be embedded in the ICC profile, and it is also set in this menu in Photoshop 5.X. In Pho-toshop 6.X, the option of embedding the profile will appear every time the image file is saved.

Depending on the output of the image, Photoshop 6. The "Off", "Retain embedded profile", and "Transfer" options in the X color management scheme have completely different effects. Let's talk about the places to note when setting these three options.

Options: Off

An image without an embedded profile will be processed within the currently defined working color space, and there is no assumed profile at the same time; if the profile embedded in the image does not match the current color settings, the profile of the original image will be Removed, this option is equivalent to eliminating the color management function.

Options: Keep embedded profile

This option is new to Photoshop 6.0. The processing of an image without an embedded profile is exactly the same as the option: "Off"; if the image embedded profile does not match the current color settings, the image is still displayed on the display according to the color described in the embedded profile, current Color settings have no effect on this image. (Note: This option should be used with caution because it is possible that the image is displayed very well on the monitor, but the color will eventually be greatly deviated when printed.)

Options: Conversion

If the profile embedded in the image does not match the current color settings, the profile is converted to the current color setting. For images without embedded profile files in Photoshop 5. A hypothetical profile can be specified in X; in Photoshop 6. X has no such option.

2. Conversion of property files

You can use the Overview to Profile (Photoshop5.X) or Convert to Profile (Photoshop6.X) submenus to open the image properties file when you open the image in Photoshop. You can use this menu when you want to apply a scanned separation profile to an image or convert a CMYK image (for offset printing) to another form of CMYK image (for gravure printing).

Note: Photoshop 5. When X saves an image, the current working color space is embedded into the image as a characteristic file. Generally, only RGB, CMYK, or Lab can be selected as the target color space. If other characteristic files are selected for conversion, for example, it is different from the current working color space. , but when saving the image, Photoshop 5. X can only embed the current working color space as a profile in the image, so it is possible to embed the wrong profile! And in Photoshop 6. In X, this problem no longer exists. The converted image of the feature file is automatically saved when it is saved.

3. Color Management in Practice

There are many options for color management in Photoshop. Below, the author lists some of the situations that often occur in production and the solutions for reference.

1) RGB scan image with profile

Most middle-to-high-end scanner software currently used in prepress companies can customize the output profile, which lays the foundation for the user to create an ideal color management model, such as: Heidelberg scanning software NewColor can be directly in the "Profilmanager" The RGB output profile is defined in the menu. Just set the output profile in the scanning software to be consistent with the "RGB Settings" menu in Photoshop, so that the image is similar to the screen display in NewColor in Photoshop, which is an ideal color management in production.

Note: ICC profiles on the PC must be stored in the "Windows → System → Color" folder; in the MAC machine is stored in the "System Folder → ColorSync profile" folder, so that you can set the color in different software The corresponding ICC profile is called in the drop-down menu.

2) RGB scan image file without profile

Many inexpensive scanners do not support the scanning of profiles, nor do they provide IT8 standard manuscripts for scan correction. However, scan profiles can also be created for these scanners because the profile creation software is completely independent of the input device! By scanning a color IT8 standard document, you can also create a scanner profile. The scanners that come with these scanners usually do not support feature files. In this case, you must use the features in Photoshop.

Open the image in Photoshop, using Overview to Overview (Photoshop 5.X) or Convert to Profile (Photoshop 6.X) in the Mode menu.

Note: After the scan profile has been created, the settings in the scanner and scanning software (such as brightness, contrast, etc.) can no longer be changed, nor can the scan software's automatic function be used, as this conflicts with the profile! If you really need to change the relevant settings, you must also re-create a profile that reflects the actual condition of the scanner.