The iPhone XS is already taking some pretty stellar low-light videos, but if you want even better results, there is a setting that can help you better visualize dimmer situations.
John Gruber of Daring Fireball points out in his iPhone XS Review:
"There is a cool XS-exclusive feature in Settings → Camera → Record Video when shooting with 30 FPS ̵1; whether in 720p, 1080p or 4K – you can turn on "Auto Low Light FPS" which will reduce the frame rate to 24 FPS if the phone thinks this is a bit dark light exposures.This may happen in the middle of the shot Space and move to a dark or turn down the lights, and the frame rate changes within the clip. "
It is noteworthy that you do not see the setting when you have your camera Set the recording to 60 FPS on, so first enable "1080p HD at 30 fps" or "4K @ 60 fps" under Settings -> Camera -> Record Video before you see the switch for "Auto Low Light" FPS. "
agree Wrinkled-eye video enthusiasts may notice the change in frame rate, but most people probably will not notice the difference. However, what you will notice is the better exposure in low light conditions in a video in times when it is really needed.