Brush Dynamics

Photoshop has long allowed you to vary the size , opacity, and color of paint according to input from a pressure-sensitive drawing tablet. Available from companies such as Wacom ( www.wacom.com ), pressure-sensitive drawing tablets respond to how hard you press on the stylus, as well as the angle of the stylus and other attributes.

Don't fret if you only have a mouse. Whether you use a stylus, a mouse, a trackball , or even a finger on a notebook trackpad, Photoshop's brush dynamics options allow you to mimic many of the pressure sensitivity features available to tablets. You can make a brush shape twirl as you paint; add noise to the edges of a stroke; spray shapes , add texture, combine brushes, or even paint in rainbows. And most of the settings work every bit as well with one painting tool as they do with another.

Brush dynamic basics

To access Photoshop's brush dynamics, have a paint or edit tool active and open the Brushes palette. From here, click the words "Shape Dynamics" on the left side of the palette. This simultaneously activates and displays the first of six panels ” which include Scattering, Texture, and so on ” devoted to brush dynamics. Photoshop also provides a series of check boxes (starting with Noise and ending with Protect Texture) that apply minor effects without displaying additional panels of options.

Note that all check boxes and options are available when using the Brush tool, but they come and go for the other paint and edit tools. For example, the Wet Edges check box is unavailable with the Pencil tool, Color Dynamics is dimmed when using the Dodge and Burn tools, and so on. Even so, the sheer amount of options available for even the most limited of the edit tools verges on fantastic. Also, each tool observes an independent set of defaults. So activating, say, Shape Dynamics, Texture, and Smoothing for the Brush tool does not turn them on for other tools. However, these options do turn on again the next time you return to the Brush tool.

To save a group of brush dynamics for use with a variety of tools, click the page icon along the bottom of the Brushes palette. Brush dynamics are considered to be part of a saved brush shape, and transfer from one tool to another. To save a group of brush dynamics for use with a single tool, visit the Tool Presets palette (Window Tool Presets) and choose New Tool Preset from the palette menu. Doing so is equivalent to designing your own custom tool that you can select from the Options bar.

Shape dynamics

Looking at the Shape Dynamics options inside the Brushes palette (Figure 1-18), you'll notice the panel is divided into three sections: Size Jitter, Angle Jitter, and Roundness Jitter. These options permit you to vary the diameter, angle, and roundness of the brush over the course of a single stroke. But the repetition of the word Jitter may be misleading. It seems to imply that each group of options is relatedto jittering ” Photoshop's word for random brush shape fluctuations ” when in fact, jittering is a minor element of shape dynamics. Jitter is actually the least important option in the panel. In any case, let's look at this panel in (what we feel to be) a more logical fashion.

image from book
Figure 1-18: The Shape Dynamics panel ” complete with several misleading references to jitter.

The diameter settings

The first group of options controls the thickness of the brushstroke. Most important of these is the Control pop-up menu, which links the diameter of the brush to one of several variables . If you own a pressure-sensitive tablet, the most obvious setting is Pen Pressure, which is the default. This setting turns the brush into a traditional, pressure-sensitive painting tool, growing when you bear down on the stylus and shrinking when you let up.

The Pen Pressure, Pen Tilt, and Stylus Wheel settings require a tablet and stylus. If you're using a mouse, selecting one of these options displays a triangular warning icon to let you know it isn't going to work. If you are using a tablet and see this little marker, try clicking with the stylus on the Brushes palette. If that doesn't work, open the control panel or utility that manages the tablet to make sure the tablet is properly installed.

In addition to Pen Pressure, the Control pop-up menu lets you select between the following options:

  • Off: This option turns off your control over varying the thickness of the brushstroke. You can still add random variations to the thickness using the Size Jitter value.

    image from book
    Adding Sparkle with the Fade option

    The Fade option can be most useful in the creation of a specular reflection, or in layman's terms, a sparkle. The figure below shows our happy-go-lucky friend from Figure 1-9 with a gleam in his eye. To add the sparkle, you can follow these steps:

    1. Create vertical and horizontal strokes: Paint a series of white strokes outward from a center point you choose to be the center of the sparkle. Using the Brush tool, Shift-drag to make each of the four horizontal and vertical strokes using a soft brush with a diameter of 20 pixels and a Fade value of 100 steps.

    2. Create diagonal strokes: To make each of the diagonal strokes, click in the center and Shift-click farther out, using a diameter of 10 pixels and a Fade value of 50 steps.

    3. Create a bright center: To complete the effect, I clicked once in the center of the sparkle with a very large, very soft brush.

    image from book
    Our stalwart beach denizen gets his iris brightened (middle), and a twinkle (right) created using the Fade setting.

    image from book
     
  • Fade: This option works every bit as well whether you use a mouse or tablet. Choose Fade to reduce the size of the brush over the course of the drag, and then enter a value in the option box on the right to specify the distance over which the fading should occur. This distance is measured in steps ” that is, the number of spots of color the brush plops down before reducing the size of the brush to its minimum (defined by the Minimum Diameter setting). The default value is 25, which means 25 spots of color. Exactly how long such a stroke is in, say, inches depends on the Diameter and the Spacing values in the Brush Tip Shape panel. Be prepared to experiment.

  • Pen Tilt: The tilt of a pen is its angle with respect to the tablet, as illustrated in Figure 1-19. Straight up and down, the pen communicates no tilt; at a severe angle, the pen communicates maximum tilt. When you set the Control option to Pen Tilt, you do two things. First, you vary the size of the brush according to pressure, just as you do when using Pen Pressure. Second, you add an element of vertical scaling so that the brush shape is oblong during a tilt. This scaling is defined by the Tilt Scale slider. All in all, it's an interesting idea, but for my money, Pen Tilt works more predictably when applied to roundness.

    image from book
    Figure 1-19: Most Wacom tablets are sensitive not only to how much pressure you apply to a stylus, but also the angle of the stylus with respect to the tablet, known as the tilt.

  • Stylus Wheel: The stylus wheel is particular to electronic airbrushes available for tablet users. Figure 1-20 shows Wacom's Intous 3 airbrush, complete with stylus wheel. Unlike the scroll wheels included with many PC mice, the wheel on an airbrush locks into position. This means you can nudge it higher or lower and leave it there. Although typically associated with properties such as Flow (which you can set from the Other Dynamics panel), the airbrush wheel is surprisingly useful for diameter as well. Move the wheel up, the brush gets thick and stays thick; move the wheel down, and you lock in a fine line, all in the middle of painting a brushstroke.

    image from book
    Figure 1-20: The airbrush stylus includes a wheel that you can permanently set to increase or decrease the flow of paint, as with a traditional airbrush.

Ok, we've seen everything there is to see on the Control pop-up menu, but what do those three big slider bars that dominate this section of the panel do? Thought you'd never ask:

  • Minimum Diameter: This option determines the thinnest a brushstroke can become.

  • Tilt Scale: This option is puzzling. Yes, it's only available when you set the Control option to Pen Tilt, and yes, it stretches the height of the brush to make it elliptical when you tilt the stylus. But why? You can do this just as well with the roundness options, as explained a little later. Again, software developers at play is my best guess. If they can give you as many options to do something as possible, perhaps that justifies the exorbitant cost of the software.

  • Size Jitter: Use this slider to add an element of pure randomness to the thickness of a brushstroke. This option works equally well with mouse or stylus. Higher values produce a wider range of jitter. Keep an eye on the preview at the bottom of the palette to get a sense of what different settings will do.

Angle and roundness

After you've got a handle on the diameter settings in the Shape Dynamics section of the Brushes palette, the Angle and Roundness settings are pretty straightforward.

  • Angle Control: Just like the diameter settings, you can link the angle of your brush to such variables as Pen Pressure, Pen Tilt, and Stylus Wheel. More pressure or tilt equals more rotation of the brush. These changes have a greater visual impact when using elliptical or asymmetrical brushes. You can also link the angle to Fade, which rotates the brush over the course of a specific number of steps and then returns the brush to its normal angle (as specified in the Brush Tip Shape panel).

    You have two additional settings on this Control pop-up menu: Direction and Initial Direction:

    • Direction: Rotates the brush according to the direction of your drag. A horizontal drag is considered the normal angle; when dragging vertically, the brush rotates 90 degrees. For maximum effect, after setting this option to Direction, go to the Brush Tip Shape panel and set the Angle value to 90 degrees (or something close) with an elliptical brush. Then raise the Spacing value to something higher than 100 percent.

    • Initial Direction: Meanwhile, the Initial Direction option rotates the brush according to the very start of your drag and then locks it into position. It's a nice idea, but the angle is locked down about 2 pixels into your drag, which means Photoshop is aware of your initial direction before you are.

  • Angle Jitter: This option rotates the brush randomly as you paint. As always, be sure to adjust the roundness of the brush so you can see the randomness at work.

  • Roundness Control: Set this option to Fade to reduce the roundness to its minimum over the course of a specified number of steps. You can also associate the roundness with Pen Pressure, Pen Tilt, or Stylus Wheel. Of these, Pen Tilt makes by far the most sense to me, because that's what pen tilt does in real life.

  • Minimum Roundness: This value determines the minimum roundness, or maximum flatness , of the brush available to the Control and Jitter settings. If the Control option is set to Off and the Roundness Jitter is 0 percent, then the Minimum Roundness slider is dimmed.

  • Roundness Jitter: Use this option to introduce random variations in roundness to your brushstroke.

  • Flip X and Flip Y Jitter: These two check boxes at the bottom of the Shape Dynamics panel give you the ability to flip the jitter on its x-axis, y-axis, or both at once, much like you can flip the brush tip shape. Flipping the jitter on its axis may be more control than most of us will ever need, but you can't fault Photoshop for offering yet another means of controlling brushstrokes.

Additional brush dynamics

The other panels of options ” Scattering, Texture, and so on ” follow the same logic you've seen thus far. Figure 1-21 demonstrates several dynamic permutations . Here's how these options work:

image from book
Figure 1-21: Several brush dynamics applied to some of Photoshop's predefined custom brushes.
  • Scattering: Highlight the Scattering option to spread the position of the spots of color around the brushstroke. When using a custom brush, the effect is like spraying a pattern of images. Raise the Scatter value to increase the spread. Select Both Axes to scatter the brush spots along the stroke as well as perpendicularly to it. Use the Control pop-up menu to link it to stylus pressure or some other variable. Use the Count options to increase the population of brush spots.

  • Texture: Select this option to apply a texture to a brushstroke, useful for conveying a surface such as paper or canvas. After selecting a predefined texture, set the Scale and Depth values to determine the size and degree of texture applied. Use the Mode option to define how brush and texture mix. (for more on the Mode options, see the section "Brush Modes" near the end of this chapter; but for now, just experiment with an eye on the preview.)

    If you want to vary the depth of texture throughout a stroke, turn on the Texture Each Tip check box. Then use the Control option to vary the depth according to, say, stylus pressure, or add some random Depth Jitter.

  • Dual Brush: The Dual Brush panel lets you mix two brushes together. Select the second brush from the list of thumbnails and use the Mode option to specify how the brushes intermix. You can also throw in settings such as Spacing, Scatter, and Count, all of which affect the second brush. Figure 1-22 shows an example. Notice how by mixing a standard round brush with one of Photoshop's predefined Dry Brush options, you can generate a complex brush that imparts its own texture.

    image from book
    Figure 1-22: Use the Dual Brush options to combine a soft round brush and a predefined custom brush to create a fairly convincing chalk effect. You can also scale and rotate the brushes to create the light eraser stamps in the corners.

  • Color Dynamics: Use these options to vary the color of the stroke between the foreground and background colors depending on a fade or stylus pressure. You can also apply random changes to the hue, saturation, and brightness, or all three. The final slider bar, Purity, increases or decreases the saturation of colors throughout the brushstroke.

  • Other Dynamics: The final set of brush dynamics permit you to associate the opacity, strength, flow, or exposure of the brush, depending on what tool you're using. Each of these attributes is discussed in more detail in the upcoming section, "Opacity and Strength, Flow and Exposure." If you happen to own an airbrush, settings such as the Flow and Exposure are what the wheel was originally designed for.

    Tip  

    You'll also notice that you can lock the settings you choose in the various brush dynamics panels. Click the lock icon next to a panel name in the Brushes palette to toggle the lock option on or off. When a panel is locked, Photoshop retains the options you set in that panel even if you select a new brush preset that normally contains different settings.

Noise, Wet Edges, and the rest

The list along the left side of the Brushes palette (shown earlier in Figure 1-18) ends with five check boxes that you can use to add highlights and constraints to your brushstrokes. Not all options work with all tools, but when available, they're as effective as they are easy to use. And they work equally well with mouse or stylus.

  • Noise: This option randomizes the pixels along the edge of a brushstroke. Because the option affects the edge only, softer brushes result in more noise. The middle line in Figure 1-23 shows an example.

    image from book
    Figure 1-23: Three lines painted with the Brush tool. The first was painted without dynamics, the second with Noise, and the third with Wet Edges. The enlarged details show how the edges of the strokes compare.

  • Wet Edges: When you select the Wet Edges check box, the brush creates a translucent line with darkened edges, much as if you were painting with watercolors. Soft brush shapes produce more naturalistic effects. The final example in Figure 1-23 shows a soft brushstroke painted in the same color as the previous brushstrokes.

  • Airbrush: This check box duplicates the Airbrush icon in the Options bar. When turned on, paint builds up even when you hold the cursor in place, as if spraying color from a real airbrush. The Airbrush option is not available when using the Pencil tool or any of the three focus tools (Blur, Sharpen, and Smudge).

  • Smoothing: If you have difficulty drawing smooth lines and curves, turn this check box on to even out the rough spots. It slows down Photoshop's tracking time a little, but in many cases, it may be worth it. Adobe recommends this option when using a stylus, but it's useful for optical mice, which are notoriously bad at tracking evenly on patterned surfaces, such as wood tabletops.

  • Protect Texture: If you plan on painting a lot of textured lines and you want your textures to match, select this check box. It maintains a consistent pattern from one brushstroke to the next. The effect can be subtle, but we usually advise working with the option turned on.



Photoshop CS2 Bible
Photoshop CS2 Bible
ISBN: 0764589725
EAN: 2147483647
Year: 2003
Pages: 95

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