Breathing refers to the shifting of an angle of view of a lens when changing the focus . Some (often higher quality) lenses are designed to lower the degree of this effect. Lens breathing does not prevent one from focusing or following focus with this lens, but it does not have the desire for any kind of focus, since it is noticeably changes the composition of the shot.  This is not the case with the aspiration and expulsion of the internal volume.
- Jump up^ “SAMPLE – LENS BREATHING” . hdslr35 on Youtube . Retrieved 13 June 2014 .