Channel Masking in Photoshop

An extremely quick and effective method for selecting a subject with a reasonable color contrast to the surrounding pixels is to create a mask and then to load this mask as a selection.

1. Click on each channel to see which channel offers the best contrast, white and black.
2. Duplicate this channel by dragging it to the new Channel icon.

Depending on the channels contrast you can do one of the following:

Method 1 – For relatively high contrast channels

1. Apply a levels adjustment to the duplicate channel to increase the contrast of the mask.
Slide the shadows, mid-tone and highlight sliders in until the required mask is achieved.
2. The mask may not be perfect but this can be modified using the painting tools.
3. Choose a paint brush, set the opacity to 100% in the Options bar, and then paint with either black or white to perfect the mask.

Method 2 – For more complex channels and those that have soft or hair transition areas.

1. With the duplicate channel active choose Image > Apply Image and in the target box choose Multiply or Overlay to get the best black and white contrast.
2. The mask will seldom be perfect so it will need to be touched up. You can use the Levels adjustment as described in method one and then
3. Make the RGB channel active to see the image and use the Pen tool to create a path on the edges that have a relatively hard edge.
4. As you create the path and you come to an edge with an hair or an otherwise soft edges click inside the soft edge and set a point, moving inside the hair edge setting points as you go.

You should now have a path which is along the hard edge but inside the soft or hair edge.

5. Create a selection from the path using ctrl+plus the Enter.
6. Fill the selection with black using Atl+Backspace
7. With the Paintbrush paint the area in the mask that should be white. Do not paint on the transition area between the white and black that contains the soft or hairy edge.
8. You now will use levels to create the mask in the transition area. You do this by selecting a relatively small area with the Lasso tool using a Feather of about five to 10.
9. With this area selected open Levels, Cctrl+enter, Drag the Shadows slider to the right and the highlight slider to the left until you get good contrast in this area.
10. Select additional areas of the transition and adjust using Levels as in the previous step. Do this until the entire transition area has been adjusted.
11. You now have a mask that can be used to extract an area from its background. This mask can be loaded by clicking on it with the Control key or by selecting it in the select > Load Selection menu.