Painting with the Brush Tool

The Brush tool is a basic tool used throughout Photoshop in various incarnations, so you’ll want to master its use as quickly as possible. The most important difference between the Brush and the Pencil tools is that, by default, the Brush tool produces soft-edged lines that Photoshop renders smoother by a process known as anti-aliasing. This is a technique that substitutes partially filled pixels along the edges of lines to produce the illusion of gradual fading. Our eyes merge the transparent pixels together, so the line looks smooth rather than hard-edged. Although jaggy edges are most apparent in diagonal lines, Photoshop applies anti-aliasing to brush stroke edges even in horizontal and vertical lines. The fuzzier the brush, the more semifilled pixels used to produce the effect.

The Brush tool shares most of the basic features found in the Pencil tool, except the Auto Erase feature is not available:
- Activate the Brush tool from the Tools palette or by pressing B (or Shift+B if you used the Pencil tool last).
- Choose a brush tip from the Brush Preset picker in the Options bar.
- Select a Mode and Opacity from the options in the Options bar.
- Drag to paint, click and Shift+click to paint straight lines, and hold down the Shift key while dragging to constrain the Brush tool to horizontal or vertical lines.
- Hold down the Alt key (the Option key on the Mac) and click in any area of color to switch the foreground color to that color.

The Brush tool has several other options to select from:
- Flow: Flow determines how quickly the Brush tool applies the paint. You can set a flow rate from 1 to 100 percent by using the Flow slider or by typing a percentage directly into the text box. You might think of it as controlling how wet or liquid the paint is. At low flow rates, Photoshop applies the paint slowly so the color is not as dark; at higher flow rates, the paint quickly reaches its full strength as you drag.

- Airbrush: Click the Airbrush button in the Options bar to switch the Brush tool (as well as many of the other tools that use brush tips) to Airbrush mode. This produces the spray effect you get with a traditional airbrush. The longer you hold down the mouse button, the more paint that pumps out of the tool, and the wider the airbrush effect will spread.

- Toggle Brushes Palette: At the far right of the Options bar is a button (a palette icon) that shows or hides the Brushes palette. It’s a quick way to access this valuable palette, and is also available with the Pencil tool and other tools that use brush tips.