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Making Channel Masks from Native Color Channels
Creating a channel mask from a native color channel, takes a few steps; however, if you're successful the effort spent making the selection is well worth it. The trick to creating a mask with a native color channel is to use the shifts of gray in one specific color channel to create the black and white areas characteristic of a typical channel mask. For example, you have an image of a model, and you want to remove the model from the background. Unfortunately, that requires selecting around the model's hair, a difficult thing to accomplish, even in the best of circumstances. To make the channel mask, open the Channels palette and examine the native color channels, one at a time. You're looking for a color channel that displays a significant shift of gray between the model's hair, and the background. For example, you click on the red channel of an RGB image, and the models hair appears dark gray, while the background appears light gray. The difference is so pronounced you can actually see individual strands of hair, standing out against the background. If you can find such a contrast, you can quickly make a channel mask.
Make Channel Masks from Native Color Channels
Open a document.
Click the Channels palette.
Click and view the individual native color channels one at a time.
Click the channel that best represents a visual difference between what you want to select and what you want to mask.
Drag the selected channel over the Create New Channel button.Photoshop makes a copy of the selected native color channel.
Click the native color channel copy.
Click the Image menu, point to Adjustments , and then click Threshold .
Move the Threshold slider left or right until you see a sharp black and white image with the black and white representing the selected and masked areas of the image.
Click OK .
Use Photoshop's painting tools with black and white to touch up the new mask.[View full size image]
[View full size image]
[View full size image]
Did You Know?You can use native color channel masks to perform image correction. Channel masks created from native color channels can be used for more than creating a mask. For example, you have a photo where the shadow portions of the image are too dark. Correct the problem by creating a channel mask that selects just the darker portions of the image, and then use the mask to control the Levels or Curves adjustments to lighten the overexposed areas of the image. |
