Mix color channels – Adobe Photoshop CS4 User Manual
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USING PHOTOSHOP CS4
Color and tonal adjustments
Last updated 1/10/2010
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Mix color channels
Using the Channel Mixer adjustment, you can create high-quality grayscale, sepia tone, or other tinted images. You
can also make creative color adjustments to an image. To create high-quality grayscale images, choose the percentage
for each color channel in the Channel Mixer adjustment. To convert a color image to grayscale and add tinting to the
image, use the Black & White command (see “
Convert a color image to black and white
The Channel Mixer adjustment options modify a targeted (output) color channel using a mix of the existing (source)
color channels in the image. Color channels are grayscale images representing the tonal values of the color components
in an image (RGB or CMYK). When you use the Channel Mixer, you are adding or subtracting grayscale data from a
source channel to the targeted channel. You are not adding or subtracting colors to a specific color component as you
do with the Selective Color adjustment.
Channel Mixer presets are available from the Preset menu in the Adjustments panel. Use the default Channel Mixer
presets to create, save, and load custom presets.
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Mix color channels
1
In the Channels panel, select the composite color channel.
2
To access the Channel Mixer adjustment, do one of the following:
•
Click the Channel Mixer icon
or a Channel Mixer preset in the Adjustments panel.
•
Choose Layer
> New Adjustment Layer
> Channel Mixer. Click
OK in the New Layer dialog box.
Note: You can also choose Image > Adjustments > Channel Mixer. But keep in mind that this method makes direct
adjustments to the image layer and discards image information.
3
In the Adjustments panel, choose a channel from the Output Channel menu in which to blend one or more existing
channels.
Choosing an output channel sets the source slider for that channel to 100% and all other channels to 0%. For example,
choosing Red as the output channel sets the Source Channels sliders to 100% for Red, and to 0% for Green and Blue
(in an RGB image).
4
To decrease the channel’s contribution to the output channel, drag a source channel slider to the left. To increase
the channel’s contribution, drag a source channel slider to the right or enter a value between -200% and +200% in
the box. Using a negative value inverts the source channel before adding it to the output channel.
Photoshop displays the total value of the source channels in the Total field. If the combined channel values are above
100%, Photoshop displays a warning icon next to the total.
5
Drag the slider or enter a value for the Constant option.
This option adjusts the grayscale value of the output channel. Negative values add more black, and positive values add
more white. A -200% value makes the output channel black, and a +200% value makes the output channel white.