1: https://www.allaboutvision.com/digital-eye-strain/is-dark-mo...
Hi Dark Themers, in an earlier life I worked in optics, designing holographic cameras for bubble chamber physics, so I know a little about focussing systems and depth of field. The iris in the eye expands or contracts to allow or restrict the amount of light entering the eye, attempting to maintain a constant luminosity on the retina so that either not too little, or not too much light falls on the cones and rods in the retina. When the iris is dilated (open) the eye allows as much light as possible into it. You can visualize the light from a point (say a pixel) that reaches the iris as a cone. The lens in the eye focuses this expanding cone back into a contracting one that comes to a point on the retina corresponding to the position of the pixel "out there on the screen".
Focusing is achieved by a muscle around the eye's flexible lens, the cillary muscle, which squeezes the lens into a more spherical shape to cause rays entering the eye to bend more, brings no objects closer to the eye into focus, or by the cillary muscle relaxing, allowing the lens to stretch back to a flatter shape, to bend rays less, bringing objects further away into focus. In old age shortsightedness is caused by the lens loosing its elasticity and remaining squeezed, and longsightedness by it losing flexibility and the cillary muscle losing strength so that the lens cannot be squeezed as much. By the time we hit our 40's many of us will suffer one of these two extremes and have to wear glasses either for reading or for driving or, in my case, for both.
Getting back to the cone of rays from a pixel that the iris and lens conspire to bring to a point on the retina, if there is a lot of light incident on the eye and the iris is undilated then this cone is much slimmer. The result of these differing cones on focus is called depth of field. When the cone is "fat" depth of field is reduced; only pixels in the same plane (actually a spherical surface, not a plane, because the retina is spherical; film cameras have planar light receptors; the eye and camera obscures etc have spherical light receptors) will be in focus; others out of the plane will produce a diffuse circle on the retina. When the cone is "slim" (because more light is incident on the eye) depth of field is increased because the size of the out of focus diffuse circle is smaller. Consequently, when there is less light falling on the eye, depth of field is reduced; the cones are fatter and as the eye roams the cillary muscle must work to alter the curvature of the lens to keep things in focus.
The implication for the dark theme is that, while it appears to have better contrast (it does not; but more on that below), the real effect is that it causes the eye to do more work than a light theme because the amount of light entering the eye is less. So both in the short term and especially over the long term the dark theme, relative to the light theme, will tire your collate muscle and cause your lens to stiffen or squish sooner. Why then, if what I'm saying is true, did all those World War Two military aircraft use white letters on a black background? My lotus europa is the same. The disc of the instrument is illuminated by a lamp so one can see it at night, and were the panel painted white then, for the same contrast, much more light would hit the eye that for white letters on a black background and the pilot's (or driver's) night vision would be impaired as the iris would contract.
I don't want to fear monger, but I do want to suggest that it is healthier and less wearing on the eyes to use light themes.
Eliot
I'm 49 and can literally watch (pun intended) how my capability to focus in the near field gets worse and worse. I've been using dark themes in the terminal for 25 years and for a couple of years tried to use dark mode also in other software as much as possible.
After reading this I really wonder if I did myself a disservice and if I shouldn't change to light mode again.
Does anyone know of more sources on this topic? And also if the effect can be reversed or at least slowed with going back to light again?
EDIT: This[1] answer on Stackexchange has some funded details.
Can’t help but feel that it is fear mongering, though. This can’t be that difficult to research. Where is the hard evidence to back this up? Your comment sent me down a rabbit hole looking for anything scientific that suggests what you’re saying, and I find nothing that implies long term damage. The quoted post is drawing a lot of assumptions.
I've had that, too, especially when Windows 10 came out, and I was forced to use it. The full-on white, on a high-contrast monitor, was a literally painful experience.
However, as others, I much prefer having the same lightness everywhere. I hate switching from a dark background terminal / editor to a light background webpage, so I set out to mitigate this somehow.
So, I've started using off-white backgrounds when I use light mode. Solarized is a bit too orange for my taste, but many other schemes are available. I, personally, use Base16 Equilibrium (both light and dark).
I use Stylus to apply a dark skin to some sites, like HN, and sometimes, I get a flash of brightness which is very jarring in the dark.
I think "dark mode" can make this worse, as it often 'pops' best with a very high brightness, which is even more blinding when running a non-dark mode app.
But I think the reason for setting the monitors to a high brightness, which I've sometimes done at work, is the awful quality of the panels. Setting them brighter makes colors pop, as you say, even in light mode.
My work laptop is one such offender, with darker hues basically indistinguishable at low brightness. However, the screen is shitty all the way, and max brightness isn't all that bright...
Isn't the fact you get migraines the issue to solve, rather than the color scheme?
Most monitors these days are way too bright, especially for the amount of ambient light coming into the room. I try to get a bunch of light into my office and it is still barely close enough for this monitor. Combine that with displays getting bigger and bigger and it becomes more understandable how it can aggravate these conditions.
Does that last part necessarily follow? Maybe doing more work is a good thing?
Or do you have a source to back that up?
Even since I learned to turn down my monitor brightness so that white on my monitor is about the same brightness as a white piece of paper in the room, I have been very fond of Prot's Modus Operandi (https://protesilaos.com/emacs/modus-themes).
So I use light mode now all the time. That said, dark mode will always look cooler.