How to Focus On an Off-Center Subject on Your Canon EOS 6D
There are lots of rules for composing photographs with your EOS 6D, and many of them can be broken. However, the off-center subject rule is a useful one. It says that when you’re photographing a person, she shouldn't be in the center of the frame.
A photograph with your subject to the right or left of center is more interesting than one where she’s smack-dab in the center of the frame. You can easily focus on an off-center subject by following these steps:
Compose your scene through the viewfinder.
Move the camera until you achieve the desired composition.
Move the camera until the center autofocus point is positioned in the middle of your subject.
Press the Shutter button halfway.
When the camera achieves focus, the green dot on the right side of the viewfinder appears. If the dot is flashing, the camera hasn't focused on your subject.
With the Shutter button held down halfway, move the camera to recompose your picture.
By holding down the shutter button halfway, the focus locks on your subject, even as you move the camera.
Press the Shutter button fully.
The camera records the image.