The concept of signal-to-noise ratio began as an abstract electrical engineering equation but has since evolved into a useful metaphor for many kinds of communication.
All communication is a chain of creation, transmission, and reception of information. At each step along the way, the useful information—the signal—is degraded by extraneous or irrelevant information: the noise. Good communication thus maximizes what’s important while minimizing the things that distract from the message.
Data ink versus “chartjunk”
The classic graphic metaphor in signal-to-noise ratio is Edward Tufte’s concept of “data ink,” the ratio of ink in a data graphic devoted to useful information, versus the amount used by distracting visual noise, which Tufte memorably labeled “chartjunk.”
Thanks to critics like Tufte, most people who care anything about high-quality communication are now well aware that they shouldn’t use loud polka-dot patterns in their graphs and charts. On web pages three factors combine to produce “webjunk”:
The desire for attention at any cost. Flash is aptly named: it’s a measure of the attention span you get for gratuitous web animation. That animated splash page or cool home page graphic isn’t going to buy you more than an instant of retinal response from a reader.
The restricted space of the screen. Even with today’s larger monitors, the web page is a small space, especially when you have a lot to pack in, as on home pages. Crowding inevitably increases visual noise because it increases accidental associations among page elements and reduces the white space so crucial to visual organization.
Lack of control over the elements of a page. Today’s home pages are often complex combinations of content from many sources; databases, RSS feeds, and text from content management systems must all coexist on the page in an organized way.
This argues for rigorous use of a few enterprise style sheets that harmonize page displays from many sources.
The “cliff of complexity”
Every data display has a zone of optimal density beyond which the increase in visual complexity rapidly tends toward noise. The lessons of Gestalt visual psychology and the visual engineering of careful information design can help you maximize the signal ratio in your pages.
We like some complexity in data displays: the “high signal” is what makes well-
designed pages interesting. But push the degree of complexity too far and you go past a point of rapidly diminishing viewer interest: the “cliff of complexity.”
