Le 23/12/2025 à 11:21, Kevin Chadwick via Dng a écrit :
>
> -------- Original Message --------
>
>> You can force dark mode for all sites that don't have a native one or toggle this functionality on individual sites.
> Just an FYI especially for coders where black themes are easier to make look
> good (not in the OPs special case).
>
> White backgrounds provide for better e.g. stronger contrast and actually reduce
> eye fatigue compared to dark themes. I learnt this when I used to train a lot
> physically and it affected my work making me research and test it out
> significantly (in contrast to the usual mantra of exercise gives you more energy
> (maybe? upto a point or maybe that's just more ready to exercise more)). It's
> interesting that coding can be more fatiguing at times than physical exercise (I
> mean harder to keep going reasonably well after short rests).

    I think the mechanism is the following: iris openning adapts to the
mean light, which is dominated by the background.

    As a consequence, when the background is black, the iris is
wide-open and the white text saturates photosensor cells, which, I
think, might be harmfull on the long term. On the opposite, when the
background is white, the iris narrows down, so that no cell is saturated
but the contrast remains good because black is always black, meaning
zero light.

    That said, maybe due to age, though still using a clear background
and black text, a white background also causes me some fatigue and I
feel more confortable with some kind of light gray background. It is
relatively easy to adjust in Xfce4-terminal, Emacs and web browsers, but
I've not yet tried with Thunderbird.

    This applies to the open windows, not obviously to the desktop
theme. The global screen brightness can also be adjusted by writing to
/sys/class/backlight/intel_backlight/brightness . First look at
max_brightness and actual_brightness to find where you are. If you are
using Sysv RC scripts, there is one named brightness which saves the
current brightness on shut-down and restores it on start-up, so that you
only need to set it once.

--     Didier