Night mode is an automatic setting which takes advantage of the new wide-angle camera that's in the iPhone 11 and 11 Pro models. It's equipped with a larger sensor that is able to let in more light, allowing for brighter photos when the light is low.
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Apple References Unreleased Sleep App for Apple Watch
In the App Store listing for Apple's preinstalled Alarms app on the Apple Watch, there is a screenshot of an unreleased version of the Alarms app with a "Sleep" label and fine print that reads "set your Bedtime and wake up in the Sleep app."
Similar functionality is available on the iPhone through the Bedtime tab of the Clocks app.
There is no Sleep app or references to a Sleep app in the Alarms app on watchOS 6.0.1 or watchOS 6.1 beta, but MacRumors uncovered evidence of Apple working on a Sleep app for the Apple Watch in an internal build of iOS 13 last month, so Apple likely shared this screenshot too early by accident.
The new Sleep app on the Apple Watch will provide users with an overview of their sleeping patterns, as well as send users bedtime and battery charging reminders. Apple Watch users will be recommended to have at least 30 percent of battery life to wear it to sleep, according to an iOS 13 string seen by MacRumors.
Apple's sleep tracking functionality is referred to as "Time in Bed tracking" based on internal iOS 13 code, with one string noting that "you can also track your sleep and get woken up silently by wearing your watch to bed."
When released, the Sleep app may have a dedicated watch face available, according to the internal iOS 13 build.
Bloomberg's Mark Gurman was first to report that Apple was testing sleep tracking on the Apple Watch. Back in February, he said Apple plans to roll out the feature by 2020 if the testing is deemed successful. This follows Apple's acquisition of the iPhone-connected sleep tracking accessory Beddit in 2017.