When you turn on notifications for someone you follow, you'll get a notification every time that they share a photo or video. To turn notifications on or off:
If you'd like to turn notifications on or off for multiple people, you'll have to visit each profile and turn them on or off individually. Keep in mind that you may get a push notification when someone you follow shares something for the first time in a while, whether or not you have notifications turned on for that person.
People aren't notified when you turn notifications on or off for them.