Masking with Channels in Photoshop | 4
Masking with Channels in Photoshop
Method 3: Advanced compositing techniques
1 The man on the ladder has been composited with a new layer into the sandy rocks image. Some of the same problems exist as in the previous examples. Colors don't match, there are varying degrees of focus, and there is a slight fringe around the man in certain areas.
2 Let's deal with the sharpness problem first. In more extreme cases, it might be advisable to either sharpen or blur one of the layers, but in this image the problem isn't clarity as much as contrast. A simple Levels adjustment is all that is required. The sandy rocks on the background layer suffer from low contrast compared with a quite strong contrast on the man layer. Make a Levels adjustment to the background layer, using the settings shown.
3 The blue fringe around the man is more noticeable in some places than others. The areas around his hair and under his forearm show up the most. To remove this, go to Layer > Matting > Defringe. Apply a Width of 1 pixel.
4 One negative aspect of defringing is the fact that it can give the layer a "cutout" appearance. Indeed, any composited layers, even those which have been wellselected and extracted from their original backgrounds can suffer from this problem. The edges look too sharp. The best remedy for this is a border selection. First, load the selection from the man layer. Keep the Ctrl/Cmd key pressed and click the man layer in the layer palette.
5 Go to Select> Modify> Border. Apply a value of 2. This enables us to blur the thin area within the border selection, thereby softening the cutout effect. Use Gaussian blur with a Radius of 1.0. The same area around the baseball cap can now been seen with a smoother edge. This process is effectively like applying anti-aliasing to the layer.
6 The image is starting to look more natural, but the main problem remaining is the difference in color between the two layers. The man has a blue cast which is particularly noticeable in the white of his overalls and cap. To fix this, select the man layer, then go to Image > Adjustments > Match Color. Go to the bottom half of the dialog box and select the current document and the background layer from the drop-down. This denotes the background layer as the one from which the calculations will be made.
7 The top half of the dialog box tells us which layer is the target layer and provides sliders for increasing or reducing the color effect. The settings shown render a flat brown cast over the man layer.
8 Drag the Fade slider to 80 to reduce the strength of the adjustment. The Luminance slider adjusts Lightness and Color Intensity adjusts color saturation. If an unwelcome color cast is generated, check the neutralize checkbox.
9 If necessary, the Burn tool can be used to darken any edge areas that are still too light. Use the Dodge tool if any areas need lightening.
Excerpted from Photoshop Retouching Cookbook for Digital Photographers by Barry Huggins. ISBN 0-596-10030-2, Copyright Â© 2005 O'Reilly Media, Inc. All rights reserved.
Created: March 27, 2003
Revised: April 10, 2006