Converting an image
→ Converting in Adobe Photoshop
1. Open an image with Adobe Photoshop.
Important: your image must be in RGB, CMYK, Lab, or Grayscale mode, and 8 Bits/Channel.
2. On the Edit menu, click Convert to Profile.
3. Click Advanced.
4. Select Multichannel mode. Select a color profile from the Profile list.
5. Select your Conversion Options.
Important: best results are reached using Intent: Perceptual
6. Select Preview to preview the effects of the conversion on the image.
7. Click OK. Your image has now been converted to multichannel.
8. On the File menu, click Save As.
In the Format list, select Photoshop DCS 2.0. Click OK.
The CMYK colors of the inks for printing are very standardized, and essentially the same for Offset printing. Because the CMYK color space is so well defined, Adobe Photoshop or InDesign can display a CMYK image very well, and a monitor can be calibrated to make it look like a print (soft proofing). Spot colors, on the other hand, are not standardized. There are more than 1,000 PANTONE colors, and programs like Adobe Photoshop cannot predict the color that results when any two of the PANTONE colors are overprinted. Particularly when the spot colors are not fully transparent, it could also make a significant difference which color is printed first and last. Spot colors cannot be processed by the normal ICC profiles, and need to be defined in Adobe Photoshop as Multichannel. Each combination of spot colors needs a special color profile.
Color Library profiles are optimized for printing and they offer the best color separation possible for your printing devices. Due to the difficulties of having an accurate preview of the printed output on your screen, here are a few tips for obtaining a more precise idea of how your image will be printed: in Adobe Photoshop, just after selecting your Profile in the Convert to Profile window and before clicking OK, the preview of the image is the closest to its final printed appearance. Adobe InDesign, with Display Performance set to High Quality, often provides a better preview than Adobe Photoshop. In any case, rather than relying on an on-screen rendition, you should always print a proof with the correct paper, halftoning, and ink density in order to obtain an accurate preview of the final results.
The two images below are intended to simulate the possible differences between multichannel screen preview and print.
→ Editing your images
The JPEG compression of input files can significantly degrade the quality of converted images; high-quality input files will provide the best results. We recommend retouching your images before the profile conversion, not after. Note that images with good contrast and saturation will generate more vivid colors.
However, after the conversion, you can still edit your images, as follows:
1. In the Layers panel, click the Channels tab and select the channel you want to edit.
2. On the Edit menu, point to Setting, and then click Curves or Levels.
Now you can edit your image in a single channels.
→ Changing color names
The Color Library profiles are designed to work with the predefined colors from the PANTONE Matching System or Risograph colors, but you can rename colors or choose another ink as follows. Please notice that this manipulation does not affect the color separation, but only change the preview color of the selected channel:
1. In the Layers panel, click the Channels tab and double-click on the channel for which you want to change the color.
2. Click the Name text box. At this point you can change the name of the color manually.
3. Click the Color box to access the Color Picker.
4. Click Color Libraries.
5. Select a color from the Adobe Photoshop Color Libraries.
6. Click OK