vizio smart tv has a very dim/dark picture

Last weekend i purchased a vizio smart tv it was on display and 100.00 bucks cheaper then the original one in the box...but anyway....once i got home i noticed that the picture is not as bright as my previous sony bravio tv...not by a longshot i might add lol but its not too bad during the day when the light shines thru my glass windows and i have a overhead light turned on but its real noticeable and annoying at night and with no lights on in the room.....anyone know what might be the cause of this?...i read online that some other people have made complaints about their vizio tvs having a backlight problem that dims in too dark at times....thats not what i'm expiercing....my picture stays the same and seems worse at night....any help will be appreciated