Using a stylus pen to draw on your iPad can be a great help when creating digital art, allowing you to produce images using the same skills you would use to create a pen-and-paper drawing. However, the iPad's touchscreen cannot recognize input from regular pens. Rather, you must use a pen with a specially coated nib, known as a capacitative stylus.

Capacitative Touchscreens

The iPad features a capacitative touchscreen. Capacitative touchscreens differ from resistive touchscreens in that they register input through electrical capacitance rather than physical pressure. When you tap a capacitative touchscreen, your finger changes the electrical field in the area of the screen you touched. By measuring capacitance across the whole area of the screen, the device can work out exactly which point on the screen you tapped and respond accordingly. This method of measuring input gives more precise results than pressure-based methods.

Regular Pens

One drawback of capacitative touchscreens is that they can only register input from conductors, as a material needs to conduct electricity in order to change the screen's capacitance when pressed. This is not a problem when using your iPad with your fingers, as the human body conducts electricity well. However, plastic or wooden objects -- such as pens -- do not conduct electricity. Even metal pens do not create enough of a capacitance change for the iPad to register input.

Capacitative Styli

Capacitative stylus pens work on an iPad's screen because their nibs are made of a conductive material. When you touch your iPad's screen with a capacitative stylus, the display's electrical field is altered in exactly the same way as it would be if you touched the screen with your finger, and the device responds accordingly. However, capacitative nibs are usually thicker than regular pen nibs, meaning that you may not have as fine control over drawings on your iPad as you do with traditional pen and paper.

Drawing With a Stylus

Capacitative styli do not require any special apps or drivers in order to work with an iPad. The conductive nature of the pen's nib effectively fools the iPad into thinking you are using your fingers for input. As such, you are not limited to using certain drawing apps with the pen. To draw with a capacitative stylus, simply open an art app, touch the pen to the display, and sketch as you would on paper.