STEPS: Using the Multichannel Mode as an Intermediary Step

1. Open an RGB image. If the image is already open, make sure that it is saved to disk.

2. Choose Image ^ Mode ^ Multichannel. This eliminates any relationship between the formerly red, green, and blue color channels.

3. Click the new channel icon at the bottom of the Channels palette. Or choose the New Channel command from the palette menu and press Return to accept the default settings. Either way, you add a mask channel to the image. This empty channel will serve as the black channel in the CMYK image. (Photoshop won't let you convert from the multichannel mode to CMYK with less than four channels.)

4. Press Ctrl+I. Unfortunately, the new channel comes up black, which would make the entire image black. To change it to white, press Ctrl+I or choose Image ^ Adjust ^ Invert.

5. Choose Image ^ Mode ^ CMYK. The image looks washed out and a tad bit dark compared to its original RGB counterpart, but the overall color scheme of the image remains more or less intact. This is because the red, green, and blue color channels each have a respective opposite in the cyan, magenta, and yellow channels.

6. Press Ctrl+Shift+L. Or choose Image ^ Adjust ^ Auto Levels. This punches up the color a bit by automatically correcting the brightness and contrast.

7. Convert the image to RGB, and then back to CMYK again. The problem with the image is that it lacks any information in the black channel. So although it may look okay on-screen, it will lose much of its definition when printed. To fill in the black channel, choose Image ^ Mode ^ RGB Color, and then choose Image ^ Mode ^ CMYK Color. Photoshop automatically generates an image in the black channel in keeping with the standards of color separations (as explained in Chapter 18).

Keep in mind that these steps are by no means a recommended procedure for converting an RGB image to a CMYK image. Rather, they are merely intended to suggest one way to experiment with channel conversions to create a halfway decent image. You can likewise experiment with converting between the Lab, multichannel, and RGB modes, or Lab, multichannel, and CMYK.

Learn Photoshop Now

Learn Photoshop Now

This first volume will guide you through the basics of Photoshop. Well start at the beginning and slowly be working our way through to the more advanced stuff but dont worry its all aimed at the total newbie.

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