Is 50% brightness can achieve 10hours of battery in normal usage?
Hi and welcome to the Forum!
Well that's hard to say, it depends how your iPad is set up also.... there are other settings which will use more battery also.
As well as turning your brightness down, turn off Auto Brightness.
Have you upgraded to OS 7? The new OS introduced many new features as well...... If you have updated, do these steps also to save on battery life.
OS 7 introduced the new Parallax effect on our screens - Settings - General - Accessibility - Reduce Motion, turn this setting on.
Background App Refresh - Settings - General - Background App Refresh, turn this off.
Automatic App downloads - Settings - iTunes and App Store - Automatic Downloads. Turn this off.
Location Services - Settings - Privacy - Location Services, limit these settings to apps you want to use this feature with or turn it off altogether.
Dynamic Wallpapers were also introduced with OS7 - Settings - Wallpaper and Brightness - only use Stills
All these steps will help you save more battery.