A) Brain. You can train yourself to use more of your whole field, but you’ll lose that attentional “spotlight” that you normally aim at things and picks out all the detail.
If you’re ever scanning something like a thick tree, looking for something, hold your arms out and form your fingers into a square frame. Use this to further focus your attention, and scan the tree in a more methodical way by moving the finger frame. You are more likely to find the thing you are looking for this way.