This is a term that gets thrown around a lot in lens reviews, but what does it actually mean? Focus breathing is the minuscule change in focal length of a lens that occurs as the focus of the lens is adjusted. And that’s really all there is to it.
How Does Focus Breathing Affect Photography?
If you shoot mostly stills, the answer is: Not much. All lenses exhibit some degree of focus breathing, and it does not matter whether the lens is a prime lens or a zoom lens. As the focus of the lens changes, so does the effective focal length, but only by a small amount. So there will be a change in angle of view as you focus, but it’s a very small change.
On the other hand, when shooting video, it can be a real issue. Unintentional changes to the focal length in video is very noticeable and distracting. If you shoot a lot of video with a digital SLR, you may want to consider buying dedicated cinema-grade lenses, which are optimized to virtually eliminate focus breathing as you rack focus. They also have smooth “click-less” aperture rings that allow for seamless changes to aperture on the fly.