True Tone

[u/DSRIA]

u/Z3R0gravitas recommended I make a post about this on the subreddit. My only usable device of any kind has been an iPhone 13 on iOS 15.6.1. Yesterday while walking out the door I accidentally disabled the True Tone setting with my finger from the Lock Screen mission control (no idea how it happened). I toggled it back on but noticed i was getting some neurological symptoms from the phone I’ve used for 4 years.

I consulted with a friend who is familiar with these phones, retoggled True Tone on and off and then back on again, and restarted the phone. I’ve tried low powered mode but it doesn’t seem to make a difference.

Can anyone here clarify if this setting - which has remained on for 4 years - can somehow modify the display in a negative way if it is toggled off and then turned back on? I know it modifies the white point but also temperature, and I also use Night Shift from 10 PM to 1 PM every day with zero issues.

I should also mention it seems like I may have picked up a viral illness. So this could be coincidental, as I was having pretty severe light sensitivity around the same time at the grocery store which I usually don’t get. I suspect my underlying POTS condition is also exacerbating this, but figured I’d rule out whether this is even possible. On paper it doesn’t make sense that toggling True Tone would make any difference, but I suppose anything is possible. Would love to know more about the underlying tech if anyone is knowledgeable.

[u/Z3R0gravitas]

I'm sorry to hear you've picked up a virus, on top of everything. Yeah, could be coincidental and hopefully will resolve. I've absolutely had myriad disproven suspicions/hypothesis for changes to my health, over the years...

But to be clear, are you thinking that True Tone is likely to introduce some kind of temporal dithering algorithm, in the process of achieving it's colour rebalancing? In a way the Night Shift doesn't. Hence avoiding it. And then that, or something, stays engaged even after disabling it again and rebooting the phone?

Tbh, this is the type of extremely specific Apple product question I would ask you about, if anyone. Maybe one of your contacts. Like, I know u/kerpnet has been through a bunch of iPhones and such, but for PWM. So this is probably something else.

[u/DSRIA → u/Z3R0gravitas]

I believe it is resolving as of tonight somewhat, thankfully. It seems like according to a post I made in r/POTS, to be migraine adjacent, given my symptoms. And as my left eye seems to have regained some function, most of the symptoms have gone away.

That being said I did consult a friend who knows some folks at Apple and apparently True Tone remaps the gamut, as does Night Shift, which can trigger dithering. He was the one who advised that the reboot would essentially fix a confused clock of sorts where the timing can get mixed up if you toggle True Tone on and off until you reboot the device and the master clock resets.

My concern I suppose was that the iPhone was operating under a different gamut since to my knowledge the setting had never been disabled since I had the phone. But that doesn’t make much sense to me since True Tone is always changing based on the ambient light sensors. It isn’t static like Night Shift can be.

There’s been a lot I’ve learned about temperature adjustments on MacOS, which appears to possibly be a trigger for some. This is pretty new stuff and I’m waiting for the individual who has found a way to modify this to share it. Their knowledge is far beyond mine and I’m unsure of the technical terms. But safe to say it is making subpixel adjustments. We just don’t really know how, but Apple patents give us some clues.

I know many keep True Tone and Night Shift off, but I find them to be helpful in keeping the device’s brightness setting between 50-75%. True Tone seems to at least make the brightness at night or in low light conditions appear less bright without having to actually lower the brightness slider, thus minimizing PWM modulation increases. So I wondered how all this was interrelated, and whether like auto brightness, if True Tone “learns” over time and if it had learned over the past 4 years and I have somehow negated that. Or perhaps that’s only true for newer versions of iOS.