Overlay

Welcome to a block of the most powerful options inside Photoshop: Opacity and Blend Modes. These include the options at the top of the Layers palette, not to mention those associated with the brush tool, the Calculations command, and a whole lot more. What these options do is blend pixels together, entirely parametrically--meaning no harm done--using math. Beautiful, lovely, gorgeous math. Read more » 

If you know anything about Photoshop's brush tool, you know it paints smooth lines in the foreground color. You can control its behavior to the nth degree from the options bar and Brushes palette. And it responds to pressure-sensitive input.

Those attributes alone would earn it a place in the coveted Photoshop Top 40. The fact that it also excels as a masking tool merely cements the deal. Read more »