Masking with Channels in Photoshop | 3 | WebReference

Masking with Channels in Photoshop | 3

Masking with Channels in Photoshop

Fine-tuning Composites

Perhaps you've spent a couple of hours using all of your skill and know-how to cut an object out of the background so you can paste it into a new image. Now you have an object with a razor-sharp edge that's guaranteed to sit seamlessly in its new environment. However, after you've pasted it in, it just doesn't look right. You can't quite put your finger on the reason why. If this sounds like a scenario you sometimes find yourself in, read on.

Method 1: Layer Blend Modes

1 The first image comes from our project on making difficult selections using channels (see page 160). The blue halo around the tree we've just pasted into the sunset scene is the result of the blue light in the original image. And, because of the position of the sun in the new image, we'd expect to see the tree and the earth in silhouette, so we have some work to do here.

2 One of the quickest and easiest ways to create a silhouette effect for the tree is to use Layer Blend Modes. At present, the tree is on the top layer. With the tree layer active, click the Blend Modes drop-down box. Multiply, Color Burn, or Linear Burn can all be used—with subtle variations in the result—to successfully silhouette the tree.

3 Here, we used Multiply to create the impression of some ambient light in the earth, rather than a fully black silhouette. The result is very effective, even though it required very little work to achieve.

Method 2:

The Burn Tool

1 We can apply the same principle using a manual tool—the advantage being that you can judge which areas need and get the most treatment. Choose the Burn tool from the Toolbox, set the Range to Midtones and the Exposure to a fairly low percentage.

2 Use the Burn tool as you would an ordinary brush. Use multiple clicks to gradually build up the desired degree of darkness. Heavy strokes at high Exposure levels cause a solid black to build up, making the image look false. Leaving some of the foreground and tree bark relatively light allows some of the original detail to come through.


In this example, the mismatch is obvious. To cover the joins, we can apply several techniques. Blurring the background slightly helps to create a more realistic sense of depth. Selecting the deer from the top layer and blurring a border selection (see page 162) helps match it in to the background. Finally, applying Levels, Curves or Color Balance adjustments, you can ensure the layers match more evenly in tone and color. We'll cover these things in more detail on the next spread.


Created: March 27, 2003
Revised: April 10, 2006