Quick links to procedures on this page:
You can adjust color and tone by making changes directly to the color channels of an image. The number of color channels in an image depends on the number of components in the color mode associated with the image. For example, black-and-white, grayscale, duotone, and paletted images have only one color channel; RGB and Lab images have three channels; and CMYK images have four color channels. For more information about these color models, see Understanding color models. Additional channels can be used to preserve any spot colors in an image. For information about spot color channels, see Using spot color channels.
Displaying, mixing, and editing color channels
Although color channels represent the colored components of an image, they are displayed by default as grayscale images in the image window. However, you can display these channels in their respective colors so that the red channel is tinted red, the blue channel is tinted blue, and so on.
You can mix color channels to balance the colors of an image. For example, if an image has too much red, you can adjust the red channel in an RGB image to improve image quality.
You can edit color channels the same way that you edit other grayscale images. For example, you can select areas, apply paints and fills, add special effects or filters, and cut and paste objects in the image channel.
Splitting and combining images by using color channels
You can split an image into a series of 8-bit grayscale image files — one for each color channel of the color mode. Splitting an image into separate channel files lets you edit one channel without affecting the others, save channel information before you convert the image to another mode, or associate channels from one mode with another mode for editing purposes. For example, if you have an oversaturated RGB image, you can reduce the saturation by splitting the image into the HSB mode and reducing the saturation of the (S) channel. When you finish editing the images, you can combine them into one image. The images are combined automatically, with equal color values applied.
You can split an image into the following color channels.
Merging channels or images by using calculations
You can modify an existing image or create a new composite image by combining channel data from one image with the channel data of another image. A merge mode calculation is performed on the pixels and applied to a specified channel, an open image, or a new file. You can use calculations to correct images by merging channels from a single image or by merging two images that were created by splitting a single image. You can create a superimposed effect by merging different images. For more information about merge modes, see Understanding merge modes.
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Click Window  Dockers Channels. |
You can display color channels by using their respective colors. Click Tools Customization. In the Workspace list of categories, click Display, and enable the Tint screen color channels check box.
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Click Adjust Channel mixer. |
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In the Channels docker, click the channel that you want to edit. |
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If the Channels docker is not open, click Window Dockers Channels or Image Channels. |
You can click the composite channel at the top of the Channels docker to view the edited image.
Images in the CMYK and Lab color modes must be split into their original component channels.
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Click Image Combine channels. |
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In the Channel area, choose a channel option and click a filename from the Images list to associate the channel with a file. |
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Click Image Calculations. |
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In the Source 1 area, choose a filename from the Image list box. |
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In the Source 2 area, choose a filename from the Image list box. |
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In the Destination area, choose a filename from the Image list box, and a channel type from the Channel list box. |
The merge mode determines how colors mix. For more information about merge modes, see Understanding merge modes.
The Calculations command is grayed if the image contains objects. All objects in the image must be merged with the image background before you can perform image calculations.
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