iOS 9.3 arrived on Monday and I positively scrambled to install it. It's the first version of iOS that I've considered installing the beta of on my phone. I was after a single feature: Night Shift.
I've been a f.lux convert for years, and I can barely touch a Mac without it after sundown. For those who are averse to warming up their displays at night, I tell them to do what the domain name says: just get f.lux. Day 1 will be weird; Day 2 will be normal; and Day 3 you'll wonder how you ever lived.
I suppose the way I coped on the iPhone was because of its smaller screen size, but there were plenty of times that I noticed it straining my eyes late at night, even when making what compensations I could: dark mode in Tweetbot, sepia mode in the Kindle app. As I began to do more ebook reading, the bright blue luminosity of the iPhone screen was what convinced me to break down and purchase a hardware Kindle. When f.lux's attempts to get their app onto non-jailbroken devices were scuttled by Apple, I complained. Color temperature is a quality of life and accessibility issue, plain and simple.
Night Shift does everything it needs to, and offers appropriate settings including custom scheduling and color temperature. (I tend to keep my nighttime temperature a little cooler than the default, both in f.lux and Night Shift. In f.lux, I also warm up my daytime display by a couple hundred K; setting a custom daytime temperature isn't possible on iOS.) One feature I miss from f.lux is the option to set a slow transition between day and night modes. I find it jarring to have the temperature change like a switch was flipped at the moment the sun crosses the horizon.
One major shortcoming of Night Shift is its inexplicable incompatibility with Low Power Mode. Since iPhones are most likely to run out of juice late in the day, this restriction creates a direct conflict. While f.lux cautions that it can take CPU cycles (and power) during transitions, it essentially operates for free afterwards; I imagine the same is true for Night Shift. And there's every indication that Night Shift is a "display filter" like color inversion and similar accessibility settings, which stay on in Low Power Mode. My only guess is that the True Tone Display in the new iPad Pro relies on the same frameworks, and since it constantly updates based on ambient sensor data, it carries battery overhead. True Tone came as a total surprise, so this could be a late-add software misstep that should be fixed in 9.3.1.
Overall, Monday was great news for my eyes. Night Shift on my current phone and the promise of True Tone Display in future iPhones are no simple Sherlocking. iOS is going on beyond f.lux.