1. Biological timing: adapting to darkness

In low-light conditions, our eyes adjust and begin recognizing details they couldn’t perceive before. The purpose of a night mode is to preserve that state.

The following IPAX simulator presents a scene we have all experienced: sitting inside a car cabin at night facing blinding lights. In this scene, we can switch between three common roadside sources. The most aggressive ones are, not coincidentally, the ones chosen by people who love inflicting high beams on everyone else.

Clicking the active light turns it off, triggering automatic adaptation to low-light conditions. Over time (accelerated in the viewer to just a few seconds), the road becomes visible. In a second stage, we transition into night vision, where we stop perceiving color and can even make out faint stars in the sky.

When we turn a bright light back on, the effect of it appearing to dim down is also part of visual adaptation: the eye moves from initial glare, caused by having vision adapted to darkness, to tolerating brightness in order to recover the cabin interior.

2. The phone as a head-on flashlight

In the next scene, we see a phone turned on in light mode inside the cabin. A secondary effect of the light it emits is preventing dark adaptation. Night vision only becomes possible once we turn it off.

In practice, the phone becomes our very own head-on truck.

The car’s built-in display is designed to prevent that blindness: in night mode, it doesn’t cause glare or wipe out vision of the surroundings. If we click that display and switch it to day mode, we see how this incorrect setting creates glare, casts a reflection on the windshield, and lights up the cabin… but without triggering bright-light adaptation the way the phone does.

If you have ever ridden as a passenger and turned on your phone (in light mode!) to check directions, the driver almost certainly asked you to turn down the brightness or shut it off completely. Because it is preferable to drive without seeing the map than without seeing the road.

Night mode is a Design System decision to ensure an application can be used under any real operational condition.

3. Halation and astigmatism: why a “night mode” is better

It is common practice to design dark mode as a negative of the light palette, replacing the white background with pure black (#000000) and black text with pure white (#ffffff).

An unexpected consequence of that design decision is strained reading for the 40% of the adult population with some degree of astigmatism.

This condition amplifies the effects of mydriasis: when the eye faces an absolute black background, it interprets that it is in darkness and dilates the pupil to the maximum. Placing pure white text over that black background causes the excess photons emitted by the glyphs to spill into dark areas, a phenomenon known as irradiation or halation.

The following simulator allows you to compare how typography behaves through the optics of an eye with moderate astigmatism, showing how 100% white on pure black creates a destructive halo.

As the IPAX simulator shows, lowering text luminance and elevating the background value mitigates extreme pupil dilation and reins in the effect. This is one of those cases where prevailing accessibility dogma (“the more contrast, the better”) proves to be a simplistic reduction, a topic Santiago Bustelo presented on at Rosenverse this past July.

Since the term “dark mode” has become popularized for any interface where text is lighter than the background, at Kambrica we propose calling “night mode” the subset that factors ergonomics into its design decisions.

To help achieve this, we developed IPAX, a model and toolset for making better design decisions grounded in the physics of light and perception. And with IPAX Foundation Layer, we help Design Systems handle this combinatorial complexity by making them scalable, accessible, and ergonomic without having to rebuild everything from scratch.

Designing for what happens in front of the screen

UI is what appears on the screen. UX is what happens in front of it: what users actually experience. Designing UX means anticipating what interfaces will provoke in people before deciding what elements to display.

The real context of applications has long ceased to be the monitors they are designed on, or the conference room projectors where they are approved. Today, moreover, digital transformation has placed screens everywhere: on vehicle dashboards, industrial consoles… and in pockets and bags, ready to enter any environment that didn’t have one yet.

If you want your App or design system to respond better to what happens in front of the screen, let’s talk.