Understanding iPad art paintbrush settings

The easiest way to explain how most digital paintbrushes work is to compare the process to ink stamps. An ink stamp is a cut-out shape that, when pressed on paper, leaves a mark. If you change the design of the stamp, you will see a different shape on the paper. If you press down on the stamp and drag it around on the paper, you will create a repeating version of this shape, which comprises a solid brush stroke. So, a digital brush stroke is essentially a shape repeating itself in the direction that you draw.

The shape of a brush is the most important element controlling the overall appearance of your painting. Most iPad painting apps come with a range of different presets for you to experiment with. Two of the most useful brushes are also the simplest: the basic circle, which is great for quick sketches and for outlining illustrations; and the soft-edged circle, which is perfect for creating smooth or realistic airbrushed shading. There are also a range of sketchy and rough brushes, which are useful for creating more natural-looking paintings because they simulate the appearance of a real paintbrush stroke. Try experimenting with the different shapes available in your app of choice and see which ones work for you.

The size setting is the most frequently used control in every painting app, and simply refers to the thickness of the line. It is usually a numeric value of pixels squared. For example, a size 3-pixel brush stroke is actually a 3-by-3-pixel repeating shape. Some apps have additional variable size settings but let's discuss that later.

The opacity setting controls the degree to which you are able to see through each brush stroke. It's similar to diluting watercolor paint with water. The lower the amount of opacity a stroke has, the less noticeable it is on the canvas against what is painted beneath. Controlling opacity is particularly useful for making subtle additions to your paintings and building up color gradually.

Spacing refers to the frequency at which a shape is repeated across a brush stroke. For example, the higher the spacing value, the more spread out the shapes are across the brush stroke. This setting is a quick and easy way to create dotted lines and repeating patterns in your artwork.

Scattering techniques add a sense of disorder to the way the shapes follow a brush stroke. Rather than repeating in a consistent direction, the shapes are distributed above and below the stroke, creating a varied effect. This can save time when painting detailed textures and patterns.

Because the iPad lacks pressure sensitivity to control the size and opacity of brush strokes, many iPad paint apps have adopted systems to reproduce analogous results. Brushes and ProCreate adopt a speed based system in which the size or opacity of a stroke varies depending upon how fast you draw. This method works, but it is incredibly difficult to control—which often leads to your having to undo and repeat brush strokes. The other system, adopted by Sketchbook Pro and ArtStudio, provides a fixed minimum and maximum value for both the size and opacity of a brush stroke. This gives you more control and more consistent results.

One of my favorite features of Adobe Photoshop is the ability to create your own custom brushes from any shape that you can design. With the release of Savage Interactive's ProCreate app, you can now do the same thing on your iPad. Just tap on a preset from the brushes menu and then choose Import Shape and Grain. In your chosen grayscale image, black will be ignored and any shades from gray to white will make up the shape of the brush. There is also the option to combine another texture image with your brush to add grain.

In ArtRage, the brushes are a little more intelligent than in competing paint apps. It features settings that artists who have painted with traditional media are more likely to be familiar with. For the oil painting brush, you can control the amount of thinners in the paint, how much paint you have loaded onto the brush, and whether the brush automatically cleans itself after each stroke. There is a watercolor brush with settings that allow color bleed, an option to paint onto wet paper, and a whole range of other traditional tools with similar variables.

This brief overview details some of the key attributes associated with digital paintbrushes. But the only way you can truly understand the value of each setting is to get into the app and start experimenting. Whenever you test a new painting app, the first thing to do is open a blank canvas and start scribbling with each brush and adjusting each setting to get a feel for what is possible. Once you get to the point where you can control the tools, then you can set about trying to create something more polished in the app.