Curvemeister Forum

Here are a couple of Curvemeister Wiki articles regarding the shadow and highlight tools.

http://www.curvemeister.com/wiki/index.php?title=Thresholding_Using_Highlight_and_Shadow_Points

http://www.curvemeister.com/wiki/index.php?title=Highlight_and_Shadow_Thresholding

This can be used instead of levels in Photoshop. 

Greg