Photoshop uses the generic term "brush" to represent any of the drawing tools. Thus, the "paint brush" tool will have a brush and the "pencil" tool will also have a brush. This is a little confusing at first but you will quickly get the hang of the terminology. Actually, it helps to think of a brush as the "drawing edge" of whatever drawing tool you are using. Thus, drawing from Photoshop's art studio metaphor, a paint brush's brush would be the bristles of the paint brush while a pencil tool's brush would be the pencil's tip.

The importance of defining the "brush" is that once defined, brushes can be customized. For example, you can change the shape or size of your brush. Think of a dull pencil point versus a sharp pencil point and imagine the different types of lines the pencils would draw. Similarly, think of the shape of a calligraphy pen versus the tip of a magic marker or even a highlighting pen. Though the default brush is plenty powerful, it is useful to get the hang of working with custom brushes because each type of brush will be better or worse in various situations.

To customize the brush you should access the "options" palette.

If you access the Brushes menu from the Options palette flyaway menu, you will see the various operations available to you.

Notice in particular the "Brush Options" and the "new Brush" menu choices. Click on either one of these and you can customize your own brush.

As you can see, there are several factors that define a brush besides size and hardness. You will also be asked to define the spacing, angle and roundness of the brush.

The spacing controls how frequently a tool affects an image as you drag. Turn up the spacing and you get splotchy lines if you drag your mouse quickly over the canvas. A low spacing will track your mouse more exactly

Angle allows you to pivot your brush shape on its axes which is really only useful on elliptical or strangely-shaped brushes.

Roundness is used to modify how elliptical a brush is A value of 100 creates a circle and a value of 15 creates a long, skinny elliptical shape.

When you draw something on the canvas, Photoshop modifies the existing pixels in the background according to the logic of painting. Thus if you paint a streak of red over a streak of blue, the pixels in the streak of blue will be changed to pixels of purple.

Thus, you can think of painting in Photoshop as involving three values: the base value, the blend value, and the result value. Brush modes modify the way this blending works. Specifically, modes specify the way in which the blend and base values will interact to create a result value. Let's look at each of the modes...

The Normal mode applies the full blend value. In the case of a painting tool, the blend color will completely coat the base color. in the case of an edit tool, the edit value will completely override the existing color.

The Threshold mode is specific for Bitmapped and Indexed Color images. Essentially, it assures that the color value of the tool is applied according to the closest available color in the color map.

The Dissolve mode, which is only available for painting tools. randomly scatters the blend color to give a rough textured non anti-aliased brush stroke.

The Behind and Clear modes are available in layered images. Essentially, they modify whether the blend color is applied to the foreground or background layer. When the behind mode is selected for example, a color will be applied behind the layer showing through only int he blank or transparent areas.

The Multiply mode multiplies the brightness of the base color and the blend to create a darker tone. The opposite effect can be achieved by using Screen

Overlay works like screen and multiply depending on the value of the base color. Specifically, the hues of the base color will move towards the blend color. Soft light works like overlay with less intensity while Hard light is more intense.

Darken darkens the base color using the blend color as a basis and Lighten lightens the base color by using the lightest value of the blend color. Difference compares the brightness values of the base and blend colors and creates a result value by subtracting the smaller from larger values.