Background lighting on the iPhone makes it possible to view your apps in all lighting conditions. However, keeping the backlight turned on all the time drains the iPhone battery unnecessarily. Use the Auto-Lock feature to automatically darken the screen and lock the iPhone after a set period of inactivity, which increases the battery life. Adjust the specific length of inactivity before the shutdown occurs according to your usage of the phone. When you set the Auto-Lock timer to a low value, you increase the length of time between charging sessions.
Tap the "Settings" app.
Select "General" on the Settings page.
Select the "Auto-Lock" option and choose a value from the list of options to set the time before the backlight dims and the iPhone locks. You can select increments of one minute up to five minutes. Selecting "Never" keeps the display turned on until you manually lock the iPhone.
Information in this article applies to iOS 7. It may vary slightly or significantly with other versions or products.
Tap the "Settings" app, select "Wallpapers & Brightness" and set the "Auto-Brightness" toggle switch to the On position. This causes the iPhone to reduce and increase the brightness of the backlight depending on the ambient light.
When you use the Auto-Lock feature, the display dims slightly before the iPhone locks and turns off the display.
The Auto-Lock feature does not prevent you from receiving calls or messages. However, if you use a passcode with your iPhone, you must enter the passcode before accessing the device again.
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