Creative Masking Techniques
for Compositing
Adobe Digital Video Evangelist George Jardine demonstrates creative masking techniques with Adobe® Photoshop®
Making complex selections and creating the most effective channel (or mask) for compositing operations in Adobe Photoshop can be a fine art. Frequently the best mask for a given image already exists, ready to be used. In this exercise, I’ll show you a method for creating a mask directly from an object in an image. This technique works best for objects on a dark background.
1. Here’s an image we’d like to composite against a background of another color—a photo of a clouded blue sky, for instance. It’s obvious that creating a selection of the bird will be difficult, especially while attempting to preserve the motion blur in the wings.
Shortcuts Throughout this document, “Command/ Ctrl” means Command on Macintosh and Ctrl on Windows systems. “Option/Alt” means Option on Macintosh and Alt on Windows. 2. It looks as if the luminosity of the RGB composite might be a good place to start creating our mask. Load the luminosity of any group of visible layers as a selection by pressing Option/Alt+ Command/Ctrl+~. Next, save the selection into a new channel by choosing Select > Save Selection. Deselect and go to the new channel.
Super-user tips!
You can load the luminosity of the RGB composite as a selection by Command/Alt+ clicking the RGB composite channel in the Channels palette, and you can easily save the current selection into a new channel by clicking the Save Selection icon at the bottom of the Channels palette.
- Use Levels or Curves to eliminate most of the mid-tones in your new mask, preserving only the darkest edges. Notice the gray tones along the blurred portion of the wings. These areas will create semi-transparency during compositing. Be sure to use a paint brush to clean up your mask channel. Set your target back to the RGB composite and load your finished channel as a selection. Drag the selected area onto the new background. Notice that the semitransparent areas along the edges are too dark as they contain some black from the background of the original image. Finish the composite by using the dodge tool to lighten these edges. Set it to Shadow mode, and use a soft-edged brush set to 80% or 90% opacity.
Dodge and burn tools
If the hue shifts when you use the dodge or burn tools, try converting your image to LAB mode first. The dodge and burn tools only affect Luminosity when used in LAB mode.
6. Here’s our finished composite. Nice.
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