There are several ways to access the system settings:
From the Ubuntu taskbar
By typing system settings in the Unity dash search box
By clicking the wheel in the top-right corner of the screen and selecting System Settings
Select Brightness and Lock
Move the slider to the left to decrease the brightness level
Note: If you don’t like to go to the System Settings to adjust the brightness every time, or if your laptop doesn’t come with a dedicated brightness control button, you can install the indicator-brightness utility to directly adjust the screen brightness from your desktop.
To install it:
Open the terminal by pressing Ctrl + Alt + T
In the terminal window type the following lines (one by one, i.e. once you enter the first line, press Enter, and repeat the same procedure for the other lines):
Another way to decrease the brightness level is via the quick access menu (control center).
To access it, swipe a finger up from the bottom of the screen and the iOS quick access menu will appear. Move the brightness slider to the left to dim the display.
Note: This feature is only available to iOS devices that run iOS 7 or later. Make sure that Control Center is available within applications and on the lock screen too. To check this, go to Settings -> Control Center.
If you have a desktop computer, or your laptop is connected to an external monitor, you can dim the display via the monitor. Some monitors have a dedicated brightness key (a sun icon), whereas on others you need to access the monitor's built in menu.
Go to Settings -> Display & Brightness -> Drag the slider to the left to dim the dispay
Note: You can also enable the Auto-Brightness feature (by moving the slider next to it). The brightness will be adjusted automatically according to the current lighting conditions, thanks to the Ambient Light Sensor.
Also, Night Shift is another feature, which will dim the screen automatically after sunset.
Siri is the virtual assistant which helps you perform various tasks such as sending a message, increasing and decreasing the display brightness, etc. Before you start using it you need to make sure that it's activated.
To activate Siri:
Go to Settings -> General -> Siri -> Move the slider to the right to activate Siri
* If you don't want to press the home button to activate Siri, you can also activate the Allow "Hey Siri" option (Siri will appear once you say "Hey Siri"), which is available only to iOS devices which run iOS 8 and later, and which is plugged in a charger.
Follow the steps below to learn how to use it:
Press and hold the Home button
You will hear two quick beeps to tell you that Siri has woken up and is waiting for you to speak (What can I help you with?)
Ask Siri to perform a task such as emailing or texting or in this case, dimming the display (e.g. Decrease brightness, Dim screen please)
Siri will automatically detect when you have stopped speaking, but you can optionally press the microphone icon to show you have finished speaking
To be able to dim the display via the Home button (by triple-pressing it), you need to enable this option:
Go to Settings -> General -> Accessibility
Tap Zoom -> Enable the zoom option by moving the slider next to Zoom
Triple-tap your device's screen using three fingers simultaneously to gain access to an additional zoom settings menu
Tap on Choose Filter and select Low Light
*This extra dimming is performed on top of your regular brightness control, which means that if you have your display on minimum, additional darkening can be achieved by using this trick
Once you have selected Low Light, scroll down to and tap Accessibility shortcut -> Select Zoom as preferred shortcut
From now on, you can instantly dim your display, whenever you want, no matter what screen you’re on, by triple-pressing the Home Button. To return back to normal brightness level, re-press the shortcut.