Using channels to change color to grayscale

Sometimes it's possible to improve the quality of an image by blending two or more color channels. For instance, one channel in an image may look particularly strong but would look even better if you could add some detail from another channel. In Photoshop, you can blend color channels with the Channel Mixer command in either RGB mode (for on-screen display) or CMYK mode (for printing). For more information on color modes, see Lesson 17, "Setting Up Your Monitor for Color Management."

In this lesson, you'll use the Channel Mixer command to improve the quality of an RGB image that you'll then convert to grayscale mode. But first, you'll use the Channels palette to view the different channels in the image.

1 Choose Window > Channels (or click the Channels tab) and drag the palette from group that also contains the Layers and Paths palettes. Place the Channels palette on your screen where you can easily access it.

Drag the Channels palette from the Layers palette to make both palettes visible at the same time.

Because the image is in RGB mode, the Channels palette displays the image's red, green, and blue channels. Notice that all the color channels are currently visible, including the RGB channel, which is a composite of the separate red, green, and blue channels. To see the individual channels, you can use the palette's eye icons.

2 Click the eye icons («) to turn off all color channels in the Channels palette except theRed channel. The colors in the Start image change to shades of gray.

All channels off except red Red channel

3 Drag the eye icon from the Red channel to the Green channel and then to the Blue channel. Notice how the monochrome image in the image window changes with each channel. The Green channel shows the best overall contrast and the best detail in the woman's face, while the Blue channel shows good contrast in the framework behind the woman.

Green channel Blue channel

4 In the Channels palette, click the eye icon column for the composite RGB channel to display all the color channels in the image.

All channels displayed RGB image

Now you'll use the Channel Mixer command to improve the image in this lesson. Specifically, you'll divide the image into two areas, the woman and the framework, and mix different amounts of source channels in each selection.

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