> However, using a light scheme with mostly text, you have a huge rectangle of LED (most of the time) white light blaring at you, which itself causes eyestrain.
I'll basically repeat my comment from below, but ergonomically set up displays meet ambient brightness, but don't exceed it (much). If you're sitting in front of a display set to 80 % brightness (~300+ cd/m²) in the evening, you're simply holding it wrong and compensate by limiting the content to dark tones only, which is a crutch at best.
That's not to say people shouldn't use dark themes. But if the reason for choosing a dark theme whenever possible is mostly "white is so bright it literally hurts my eyes", then the environment is decidedly wrong and needs fixing.
Over-bright displays relative to the ambient light are definitely an issue. I've found myself feeling much less strongly about light vs dark since I installed some LED strips on the back of my monitors as bias lighting. (I didn't want to dim my monitors much more because you do lose contrast when the backlight is low)
Contrast ratio is largely independent of backlight brightness. Intuitively this makes sense, because the panel is essentially just an adjustable light filter, which you'd expect to behave linearly.
I have three screens. I adjust the brightness on all of them twice per day, but you couldn't pay me to navigate the on screen displays with the mushy buttons more often than that.
> I'll basically repeat my comment from below, but ergonomically set up displays meet ambient brightness, but don't exceed it (much).
This is true in a world where many UI backgrounds are close to "white", i.e. maximum brightness. That in itself is an unfortunate situation (though driven in part by the technical limitations of display technology until now) because there are plenty of cases where you actually do want the ability to display above ambient brightness, just not for what is meant to be a neutral background. HDR displays are designed for high peak brightness and shine with photorealistic content - pun intended.
Content such as games, video, photos all have in common that their colour/brightness histograms are much less skewed towards the extremes than typical UIs which are dominated by large uniform, mostly bright areas. Those should be limited to ambient brightness, and ideally on a true brightness plane, not clipped to the faces of an RGB cube.
I'll basically repeat my comment from below, but ergonomically set up displays meet ambient brightness, but don't exceed it (much). If you're sitting in front of a display set to 80 % brightness (~300+ cd/m²) in the evening, you're simply holding it wrong and compensate by limiting the content to dark tones only, which is a crutch at best.
That's not to say people shouldn't use dark themes. But if the reason for choosing a dark theme whenever possible is mostly "white is so bright it literally hurts my eyes", then the environment is decidedly wrong and needs fixing.