The key to using the iPhone is the battery. Appliances can't do anything without power, and their attention is distracted when the battery is about to run out. That's why we enable “low power mode”, set the automatic lock time short, and make energy saving efforts.
In particular, it is effective to reduce the frequency of communication and reduce the brightness (brightness) of the display. In particular, the latter is considered to be the biggest factor that consumes the battery in all smartphones, not just the iPhone, and reducing the power consumption is directly connected to the battery.
To decrease the brightness of the display, use the “Brightness” slider in “Settings” → “Display and brightness” or the brightness adjustment bar in the control center. If “Automatic brightness adjustment” on the “Settings” → “Accessibility” → “Screen display and text size” screen is enabled, the brightness is reduced in bright places such as outdoors, and the brightness is increased in dark places. Let's use it together.
However, even if the brightness adjustment bar is lowered as much as possible, some brightness remains. As your eyes get used to it, you can see it to the point where you don't need it, so you might want to reduce the brightness a little more. I can't do that … I don't.
Let's pay attention to the "Reduce White Point" switch in "Settings"-> "Accessibility"-> "Screen Display & Text Size" screen. This switch is used to lower the brightness of bright colors such as white, but it also has the effect of reducing the display brightness beyond the range of the brightness adjustment bar. If you do too much, it will be indistinguishable level, but even this can darken the iPhone screen.