Focus Breathing Calculator
Calculate and understand focus breathing in lenses. Focus breathing causes the focal length to change as you adjust focus, affecting framing.
Lens Measurements
Nominal focal length when focused at infinity
Measured focal length at minimum focus distance
How to Measure
- Set lens to infinity and measure subject size in frame
- Focus to minimum distance without moving camera
- Measure the apparent size change of distant subject
- Calculate effective focal length from size ratio
Focus Breathing
11.8%
Moderate
FFocal Length Change
10.0 mm
IFOV at Infinity
23.91 deg
CFOV at Close
26.99 deg
VFOV Change
3.08 deg
Analysis
Magnification Change1.133x
Image Size Change13.3%
FOV Change12.9%
Video Suitability
Acceptable for video
About Focus Breathing
- Cinema lenses minimize breathing for smooth focus pulls
- Photo lenses may have significant breathing
- Internal focusing lenses often breathe more
- Nikon Z and some Sony lenses have breathing compensation