1. Tap Apps from the Home Screen. You will be prompted with the Apps window.
2. From the Apps screen scroll and tap Settings. This action will bring you to the Settings menu.
3. From the Settings menu options, locate and tap on Display. (It’s found under Device sub-items).
4. You will then see the Display sub-menu. Tap on Brightness option under Screen menu. You will see a new screen where you can adjust the brightness level.
5. If you want to apply automatic brightness, tap to check on the checkbox for Automatic brightness. If Automatic brightness is uncheck, use the slider to the brightness level you desired instead. Just tap and drag the slider.
6. Tap OK once done.
7. On the next screen, tap Screen timeout option.
8. Screen timeout duration options will then show up. Tap on the time setting you desired (Typical options range from 15 seconds to 10 minutes.
Congratulations! You now have adjusted your Galaxy S3′s backlight settings.
For quicker adjustment on your phone’s brightness settings, access the Brightness Screen by tapping and dragging down on the Notification bar and adjust the brightness level you wanted.
Following this tutorial is optional, thus, we shall not be held responsible for any potential damages that may transpire on your device during or after the entire settings modification process. Nevertheless, it is very unlikely for a device to get damaged, for as long as you follow the steps precisely as mentioned in this page.