Here's a useful trick for iOS to dim the brightness further than control center allows.
It's a pretty hidden feature and I'm not sure what Apple's intention for this setting was, but either way, it's quite useful for reading at night.
Unfortunately, it seems this won't help preserve battery life (it's a software filter and not a physical dimming of the backlight).
Done! Now, when you triple click your home button, it should activate the Low Light filter.