This technique uses the information embedded in the image itself to create an accurate mask for complex subjects.
Click on the CHANNELS tab in the navigation panel on the right hand side.
Find the Channel with the greatest separation between hair and background.
Click the ‘LOAD CHANNEL AS SELECTION’ button in lower right hand corner:
You will get an odd pattern of the crawling ants indicating a selection has been made …
Turn on all the Channels again by clicking on the check box next to the RGB channel:
Invert the Layer Mask by clicking CMD+I
Note that the subject is transparent because of the gradients in the mask.
In the next step we will convert the mask to just back and white.
With the Layer Mask still selected (note frames around the thumbnail) got to MENU: Image / Adjustments / Threshold
Adjust the Threshold slider to find the best separation between hair and background:
Paint in the patches of transparency in the subject using a white brush (B for Brush)