Definition
What is focal length in video?
Focal length is an optical property of a lens, usually expressed in millimeters. At the same sensor size, shorter focal lengths show a wider angle of view and longer focal lengths show a narrower view.
Focal length works with camera position to shape the image. To keep a subject the same size with a wider lens, the camera moves closer; with a longer lens, it moves farther away, which changes the apparent relationship between subject and background.
Lens labels must be understood in relation to sensor format because the same millimeter value covers different fields of view on different formats. Editors benefit from this knowledge when matching coverage and planning crops or reframes.
Example in the edit
A cinematographer changes from 24 mm to 85 mm and repositions the camera, making the background appear more compressed behind the actor.
Why editors use it
It affects framing, perspective, depth cues, and how well shots will match, not just how close the subject looks.
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Quick answers
Frequently asked questions about Focal length
Does focal length alone determine perspective?
Camera position determines perspective. Focal length determines angle of view, and changing it often leads the camera to be repositioned, which changes perspective.
What is a short focal length?
On a given format, it is a lower millimeter value that provides a wider angle of view.
Why does sensor size matter?
A lens projects the same image, but a smaller or larger sensor captures a different portion of it, changing the field of view.