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:
- 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
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.
- 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 By default the Channel Mixer converts an image to grayscale using the data from the Red channel.
- 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 Get a better black-and-white image by using data from all the color channels, not just the Red channel.