It’s a shade familiar to BMW drivers who aimed their roundel at the dark horizon in the Eighties: the signature red-orange glow emanating from the instruments and buttons. What made those old BMW gauges seem perfectly attuned to night driving? Just ask the 19th-century Czech anatomist Johann Evangelist Purkinje, who was first to describe what became known as the Purkinje effect. Imagine the red-tinted war room in a nuclear sub or the glowing orange instruments in a dark airplane cockpit, and you’ll understand the Purkinje effect’s practical application. In near darkness, our vision thrives on that particular wavelength of light.
This story originally appeared in Volume 10 of Road & Track.
Broadly speaking, your eyes have two types of receptors: Rod cells handle low-light environments, and cone cells process brighter light. That red-orange wavelength sits in a sweet spot, visible to your low-light rods without saturating your bright-light cones. Your dark-adjusted eyes can seamlessly move from the road to red-orange gauges. Conversely, cone cells are highly sensitive to blue, green, and white lighting at night—the Purkinje shift. On a dashboard, these hues force a jarring handoff between your dark- and bright-vision circuits, forcing your eyes to readjust every time you glance at your speedo.
That problem manifests inside modern vehicles, too, with brands jockeying for screen supremacy, stuffing interiors with ever-larger digital panels. It’s no surprise that a bright foot-wide screen will lead to extra eyestrain. So we’re begging automakers: Downsize the screens and bring back that red-orange glow. For safety, of course, and a tiny bit of nostalgia.