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Misunderstood Photoshop: Channels

Article Description

In the eighth part of her series on handy Photoshop tools that are often overlooked or misunderstood, Helen Bradley discusses channels, a feature that not only provides information about your image but can also be used for photo editing. You learn how to use channel data to convert an image to black and white and even how to save a selection in a channel for reuse later on.

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Using Channels

There are a number of ways to use channels when working with your photos—one is when converting an image to black and white.

Typically you might convert an image to black and white by choosing Image > Mode > Grayscale to discard the color information. While this is simple to do, the results are often lackluster. On the other hand, using channels to make the conversion enables you to create a more compelling result.

To convert to black and white using channels, follow these steps:

  1. Open the photo and choose Layer > New Adjustment Layer > Channel Mixer and click OK (see Figure 2). Using an adjustment layer protects the original image and gives you a solution that can be easily altered or removed.
    Figure 2

    Figure 2 When converting an image to black and white using channels, use a channel mixer adjustment layer so you can edit the result if necessary.

  2. When the Channel Mixer dialog appears, click the Monochrome checkbox to convert the image to grayscale. Notice that in the Source Channels area, the Red channel slider is shown at 100%, indicating that the conversion is being made on the basis of the data in the red channel.
    Figure 3

    Figure 3 By default the Channel Mixer converts an image to grayscale using the data from the Red channel.

  3. To achieve a more interesting result, adjust the sliders for the Red, Green, and Blue channels so you vary how much of each channel’s data contributes to the grayscale image (see Figure 4). For example, using data from the Blue channel will intensify the darker areas of the original image. However, it will also blow out some of the highlights, so you might want to compensate for this by adjusting the other channels. The ideal end result is that the three percentages, when summed, total 100%.
    Figure 4

    Figure 4 Get a better black-and-white image by using data from all the color channels, not just the Red channel.

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