IPhone decreasing the brightness to the lowest level will not only makes it convenient (especially at night) but also will reduce battery usage. If the default brightness level is still too low in the iPhone bright for your eyes, you have the option to lower it below the default level. This way you can do even without having to jailbreak your iPhone.
- Swipe up from the bottom of the iPhone screen. In the Control Center, change brightness to the lowest level.
- Go to Settings, navigate to General> Accessibility> Zoom
- Scroll down, turn on "Show Controller" setting
- Go back one page, scroll down to the "Accessibility Shortcut"
- Select Zoom. Now you can access the menu by clicking 3x Zoom on the Home button.
- Go back to the Home screen, click the Home button to bring up 3x Zoom menu.
- Tap Choose Filter, select the Low Light.
Next you will find the screen becomes dimmer and more comfortable on your eyes. You can remove the zoom menu by tapping on the outside. Furthermore, you can enable / disable this mode with the help of 3x-click the shortcut that you set in the previous step.
Dim the iPhone screen below the default level will help you to read at night when the lights turn off the room you have. Most ebook reader is already equipped with night mode, but if the eBook reader applications that you use do not have a night mode, you can use this trick to activate night mode in all applications.
In addition to the above, you can disable the controller by opening Settings> General> Accessibility> Zoom, tap on the toggle Show Controller to turn it off.