Illustrations in Technical Documents

Visual Information

• stimulates interest
• surfaces selected arguments and benefits
• maps out document to increase readability

If you're describing an object you'll probably need a drawing or diagram of the thing. If you're describing a process you'll probably need some illustration of how it is done.

In instructions, simple drawings are common, with relatively little detail. This allows the reader to focus on the instructions and not on the object.

In definitions, more detail is typical. You could still use line drawings, even done by hand, with shading and depth perspective. Alternatively, you could use photographs. Or you may use a diagram; these are more abstract and schematic (for example, a wiring diagram of a clock, which does not resemble the physical thing at all).

Beware chartjunk. Chartjunk consists of decorative elements that provide no data and cause confusion. Edward Tufte discusses the rule of 1+1=3 (or more): 2 elements in close proximity cause a visible interaction. Such interactions can be very fatiguing (e.g., moiré patterns, optical vibration) and can show information that is not really there. Techniques to avoid chartjunk include replacing crosshatching with (pastel) solids or gray, using direct labeling as opposed to legends, and avoiding heavy data containers.

Things to consider in using illustrations

• Keys

• Titles
• Cross-References
• Location within the document
• Size of the illustration
• Placement within the margins
• Level of technical detail

Source of illustrations

• Make your own

• Photographs
• Scanning
• Clip art / internet graphics (try Google images)