What Is Focus Breathing?
Focus breathing is term that is used to describe the small change in focal length of a lens that occurs as the focus is adjusted from infinity to MFD, or vice versa. If you look through the viewfinder of your camera and rotate the lens’ focus ring from one extremity to the other, you will see that the lens appears to zoom in or out very slightly. This change is called focus breathing.
For still photography, focus breathing won’t make any difference at all. Even the most expensive professional grade lenses exhibit focus breathing, and it doesn’t matter whether the lens is a prime lens or a zoom lens. Even if you are shooting in a servo focus mode, the small focal length change as you track an approaching subject, is so small as to make next to no difference to the framing of your image.
When shooting video though, focus breathing can begin to be a distracting issue. As focus is adjusted throughout a video shot, you will notice a visible, if slight, zooming motion to the shot. Proper professional cinema lenses cost much more money than lenses for still photography and it’s their lack of focus breathing that often contributes to this high cost. Cinema lens optics are far more precise than those of still lenses, and when they are designed, they aim to have no focus breathing at all.
Go ahead! Grab your camera and take a look through the viewfinder while you rack the focus ring back and forth on the lens. If you look at the edges of your viewfinder frame, it should be pretty obvious that the lens is zooming in and out very slightly.
- What Is A Follow Focus?
- What Is A Cinema Lens?