Focal Length
0x920aAlso: FocalLength
How zoomed-in the lens was, in millimetres.
Focal length describes the lens's angle of view. Short focal lengths (16–35 mm) are wide angle; long ones (200 mm+) are telephoto and magnify distant subjects.
On cameras with smaller sensors, the FocalLengthIn35mmFilm tag gives the equivalent field of view so you can compare across cameras.
This is the physical focal length of the lens, not the field of view. A 23 mm lens on APS-C frames like a 35 mm lens on full frame, so comparing the raw number across sensor sizes is meaningless. The comparable figure lives in a different tag, FocalLengthIn35mmFilm (0xa405), which many cameras never write.
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