Mở một hình ảnh RGB. Nếu hình ảnh đã được mở, hãy chắc chắn rằng nó được lưu vào đĩa. 2. Chọn ảnh ➪ Chế độ ➪ đa kênh. Điều này giúp loại bỏ bất kỳ mối quan hệ giữa các kênh màu sắc trước đây là màu đỏ, màu xanh lá cây và xanh dương. 3. Nhấp vào biểu tượng kênh mới ở dưới cùng của Channel Palette. Hoặc chọn lệnh New Channel từ menu palette | Chapter 4 Defining Colors 177 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
