The previous section described a good generic setup for converting RGB or Lab color space images to CMYK for standard prepress printing in North America. This next set of instructions should be used for fine-tuning your CMYK gamut conversion. You may want to use this custom CMYK setup if you are unhappy with the results you are achieving when using the standard profiles. You can also use this setup in place of any custom profiles you have not received from your printing company. If you know where your job will be printed, it is a good idea to discuss the following setup information with your prepress manager, who can help you make your choices. This section and the next show how to set up the Custom CMYK dialog box:
1. Open and make a copy of an image that requires RGB-to-CMYK conversion, or make a duplicate copy of the RGB image you already have open. When you name this image, include CMYK at the end of the filename (for example Alaska Light_CMYK), so you can tell at a glance that it is a CMYK file. Converting the copy protects the color integrity of the
original RGB image.
2. If it is not already open, activate the Color Settings dialog box (Edit ➢Color Settings or F/Ctrl+K). Now choose Custom CMYK from the top of the Working Spaces CMYK menu. ACustom CMYK dialog box appears (Figure 13.36). This dialog allows you to create a custom CMYK color profile manually in Photoshop.
3. Click the Ink Colors pull-down menu and select one of the SWOP choices: SWOP (Coated), SWOP (Uncoated), or SWOP (Newsprint), depending on the type of paper on which your images will be printed. We will assume a coated stock and choose SWOP (Coated) here.
4. In the Dot Gain menu, choose Standard (the default value), and enter a dot gain value in the Dot Gain window; 20% is a standard value, but it is best to obtain this value from your printing company. If you are printing on some other type of CMYK output device, you may want to experiment with various values here to achieve the overall lightness you prefer.
Alternatively in the Dot Gain menu, choose Curves. This will allow you to control the dot gain for each of the four inks separately. For commercial printing, obtain the Dot Gain choice and values from your printing company. For other types of printing, these curves can be adjusted to suit a specific output device and paper stock. These curves can also be used to manually correct for the color cast of an output device (by adjusting the individual color curves found in the Dot Gain dialog) if no other neutralization methods are available.
1. Open and make a copy of an image that requires RGB-to-CMYK conversion, or make a duplicate copy of the RGB image you already have open. When you name this image, include CMYK at the end of the filename (for example Alaska Light_CMYK), so you can tell at a glance that it is a CMYK file. Converting the copy protects the color integrity of the
original RGB image.
2. If it is not already open, activate the Color Settings dialog box (Edit ➢Color Settings or F/Ctrl+K). Now choose Custom CMYK from the top of the Working Spaces CMYK menu. ACustom CMYK dialog box appears (Figure 13.36). This dialog allows you to create a custom CMYK color profile manually in Photoshop.
3. Click the Ink Colors pull-down menu and select one of the SWOP choices: SWOP (Coated), SWOP (Uncoated), or SWOP (Newsprint), depending on the type of paper on which your images will be printed. We will assume a coated stock and choose SWOP (Coated) here.
4. In the Dot Gain menu, choose Standard (the default value), and enter a dot gain value in the Dot Gain window; 20% is a standard value, but it is best to obtain this value from your printing company. If you are printing on some other type of CMYK output device, you may want to experiment with various values here to achieve the overall lightness you prefer.
Alternatively in the Dot Gain menu, choose Curves. This will allow you to control the dot gain for each of the four inks separately. For commercial printing, obtain the Dot Gain choice and values from your printing company. For other types of printing, these curves can be adjusted to suit a specific output device and paper stock. These curves can also be used to manually correct for the color cast of an output device (by adjusting the individual color curves found in the Dot Gain dialog) if no other neutralization methods are available.
Custom Prepress Gamut Conversion
![Custom Prepress Gamut Conversion]()
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