Rectangle in live view

The rectangle indicates the autofocus area, you want to position it over the area to be in focus.

Since you are likely using manual focus, there are several options depending on quick AF or live AF, start reading at about page 207 in the manual.

I don't believe you can turn off the white rectangle when live AF is selected.
 
Upvote 0
I think if you flip that switch, it'll remove the green box:

eos_5d_miii_live_view_button__hero.jpg
 
Upvote 0