Sometime the lowest iPhone screen setting can still be too bright in very dark rooms and disturb other people.

The Reduce White Point setting lets you make it darker still.

You can still fine tune the brightness with Reduce White Point enabled.

To enable it, open Settings > General > Accessibility > Display Accommodations

Turn on Reduce White Point and choose a value that suits - somewhere between 75-85% is a good starting point.

To quickly enable it, go back to the main Accessibility screen and scroll down to Accessibility Shortcut

Make sure there's a tick beside Reduce White Point. You can then add the Accessibility Shortcut to Control Centre.

Open Settings > Control Centre > Customise Controls. Scroll down, add Accessibility Shortcuts and move where you want.

You can then bring down Control Centre and enable or disable Reduce White Point from there.

Alternatively, you can triple click the Side button (or Home button on older phones) to turn it on or off.