The closer we stand from the object of the photo, the more blur his background. The closer the photo object, the lens focus is also closer and the depth of field will further narrow. Try to do this: thrust your index finger near the glass that is about 50 cm in front of you, focus your eyes on the index finger, now move the index finger close to your eyes. The closer the index finger with the eyes, the glass behind it will blur is not it.
