I remember a quote from my design school days (although I can't find the source now so I'm just going to claim it as my own) :

"That type reads best which is read most."

As I recall it was in defense of serifs on typographic characters – long believed to aid line scanning in books – which is to say "Whatever people get used to reading, that's what's best to read." While at the time would have pertained to print, now the same circular logic has been applied to digital spaces & interfaces.

I'm a staunch supporter of dark mode as the default for interfaces and I'll tell you why. Paper is a relatively recent invention yet it has shaped the way we feel about our visual spaces. Before around 2000 years ago, hominids had a different norm for visual processing. I’ve been reading around about the subject and I’ve heard good arguments on both sides, but indulge me an amiable rant . . .

For years coders have used an inverted color scheme in their coding apps : light text on a dark background. My recollection of the "coding area" in previous agencies & studios I've worked at in the past is that it was a dark corner or room where the light levels were kept low. Now I don't know if this was cultural – recreating the environment of the coding all-nighter in the dorm or apartment, or maybe the university computer lab – or in response to the particular rigors of the work – long hours spent staring meticulously into a computer display – but the feel of the space always resonated with me. I'm a low-light person in general, at least in comparison to most people I know.

I know the justification is that the lighter characters on a darker background is less eye-straining and so eases the day's labor. They even buck the print-born practice of keeping line lengths to a trackable length, as they are seldom reading code in that repetitive, linear fashion we all know from books & articles, letting text stretch out across the full width of huge monitors. So what are the rest of us doing defaulting to dark characters on light backgrounds? Surely the inversion would benefit the rest of us.

Perhaps it's the difference of us mostly looking at our phones and computer screens in daylight conditions and so the complementary brightness of a screen matches our environment. I doubt it. More likely it’s a throwback to print and the legacy of white paper with dark ink that we’re all so familiar with (and the attendant psychological comfort we take from its’ familiarity). So how should we best design digital interfaces to indulge the physiology of the human eye (while acknowledging the needs of the human mind as well I suppose). What model should we be imitating? Let’s look backwards for answers . . .

When early computer monitors were created, they were dark backgrounds with lighter – often bright green – characters. The CRTs of decades past were beholden to the technology of that scanning rays’ bright beam tracing figures on an unlit surface inside the tube. It wasn’t until Apple came along with their desktop metaphor that we started to see white shapes with dark characters on a computer screen more reminiscent of print. Even the early Xerox interface Apple copied was light figures on dark fields. The Apple interface was full of skeuomorphic metaphors of pages, books and stickies necessitating a light space with darker shapes. Even Apple’s rudimentary coding platform (Hypercard) transitioned the activity of coding into black on white (although their current Terminal app nods to the coding culture custom of light on black). But I submit that Apple’s move to dark on light was more about making users feel comfortable with the space they were operating in than choosing the color scheme that was best for human eyes.

Likewise, the color scheme of early printing was more an outgrowth of the technology of the time than an intentional choice made as physiological accommodation. If we want to go all the way back to the Stone Age, we see relatively light substances like sandstone inscribed with comparatively dark grooves resulting in a dark on light model. Fast forward a while and we find papyrus reeds comparatively light in color next to the marking methods used at the time. Two communications technologies that wound up just using the incidental color scheme of the materials used. But then again these went on for thousands of years and as a human culture we’re all used to digesting information in that scheme. Is this the paradigm we should be attempting to recreate with our digital interfaces? Surely thousands of years of dark on light have had some impact on our physiology. I would say we can go back even farther than that.

Evolution happens slowly, and while we have several dozen generations of reading dark on light thanks to Kai Lun and Gutenberg and others, we have hundreds of generations of doing precise work with our hands that predates the print tradition. For millions of years our ancestors were digging roots out of rich soil, plucking bright fruit from dense foliage, shaping stone, bone and wood into tools with dark-skinned hands often by firelight. When I think of the precise work that the human eye has had time to grow accustomed to (and so presumably favors), it’s light on dark work. I’ll wager there are plenty of counter examples in the ancient world, but those cited here seem a pretty strong preponderance. Modern man is unique in history to live in light-flooded interiors. The hominid sensing eyes shining through the night, the ship’s captain measuring stars in an inky sky, the smith at his hearth, the baker, the seamstress, all those that work with their hands in dimly lit houses and workshops throughout history: their focus is largely light objects in comparatively dark environments. Surely this legacy outweighs a few centuries of print when considering how to satisfy the eye.

Providing both a dark and light option is a growing trend in interface design. Both Apple and Android have this as an option at the system level and can also sense when to switch automatically based on environmental light levels. I choose to have most of my digital spaces dark full-time by default and find this easier on the eyes even in daylight. It might be my affinity for low-light environments, or maybe my affection for National Parks signage with their routed, yellow grooves on dark wood, but I prefer dimmer surfaces when I need to focus. I don’t think we should be asking ourselves ”Well, what are people used to reading?” It should be the broader question of “What schema is best for the focus of the mind?” Although I’m guessing the mind will follow the needs of the eye as it has done with the necessities of print.

Let’s let our eyes and our mind drift back in time to an age where our environment wasn’t so fluorescent, when work had a slower pace, when the things we were concentrating on were more of a bright spot in our field of view. Even Apple's Night Shift (automatic dimming of contrast and shifting of white point) acknowledges what we all know to be true : so much of our reading these days happens in the darkened intimacy of our bed. Why not make this the default mode rather than the exception? It's where the human mind feels most comfortable. Man, that conclusion got really grandiose. And then trivial. And yet somehow too short. I’ll definitely need a better conclusion for the TED talk.

Dark mode rules!