I have a canon T3i, and when I look through the viewfinder and take a picture, the picture comes out fine. However, if I try to take a picture through the LCD screen, the screen shows two blue lines and when i take the picture, it gets cropped on those lines. Anyone knows what settings to change to avoid this?
It's on page 129 of the EOS Rebel T3i/600D Instruction Manual
It appears your camera is currently set to 16:9. To do what you want, you need to set it to 3:2.