Dark mode, for the first time ever, has legitimate, objective reasons to want, now that we have pure LED displays: a black LED pixel consumes no energy.
CRTs consume so much power that the beam current is negligible. The comparison is with backlit LCD screens, which have to have the backlight on regardless of how many black pixels you have.
Actually traditional tft displays need to apply a current to turn a pixel black, so if you don't use adaptive brightness that would dim the backlight if the display is mostly black, you actually consume more power with a black theme. I have a low power Pentium notebook with 15" led backlit screen and the difference between a terminal with black or white background is significant.
Battery at 74%. Sitting at black screen for about a minute, the highest estimate I got was 4:50, lowest 4:05. It was mostly showing numbers close to either of these, almost never something in between.
Switching to white I got 5:40 and 4:50 showing pretty much the same behavior.
It's an HP pavilion 15-p005ng with a Pentium N3530. Terrible machine btw. Linux freezes in irregular intervals, almost immediately with OpenGL stuff...
I'm pretty sure that's how it works. The drivers report total battery capacity, current battery capacity, and current power draw, so the meters just do the math.
I remember my high school electrical engineering teacher challenging me to make a project out of comparing ways to save power with CRTs and LCDs. All black vs. all white screen had no measurable difference on my multimeter. I couldn't answer it at the time. I was convinced that it should save power.
I regularly get migraines, where "bright" lights are searingly painful to look at. When the symptoms aren't too bad, dark themes on a text editor are okay, but light themes are not.
Migraines aren't an uncommon problem.
I think that is a fairly objective reason driving the preference.
I dislike sites with dark background. Maybe it is a problem with my poor quality LCD screen, but I switch to reading mode on such sites (so that the background becomes white) because they are hard to read.
I'm pretty much the exact opposite. I typically use my computer/phone in a low light environment (monitor and phone are almost always on lowest brightness settings), and a white background hurts my eyes. I use a dark background wherever possible, especially when reading ebooks/longer articles on my phone.
Any good software designed for reading should have good support for both.
Don't most dark themes actually use dark grey rather than black? The material design dark theme guidelines [0] were posted recently and recommend dark grey as the primary surface colour.
Backlight control for dynamic range is common, but not necessary for being an “LED display.” It just means the backlight uses LEDs instead of CCFLs like they used to.
It's a display and it "has LED". Given a clean slate language reboot for today's technology we would probably reserve the term "LED display" to "LED per subpixel" models and call LED LCDs "LED backlit", but the term got into widespread use when the backlit kind was the only one available so that's where we are now.
