What does focal length mean?

In the pinhole camera model, the distance from the pinhole to the image plane, given in pixels for vision work. An object of width W at distance Z appears f * W / Z pixels wide.

Also written as: focal lengths

In a lesson

f is the focal length in pixels, and (cx, cy) is the principal point, where the optical axis pierces the image. That is the whole of the pinhole camera. Real lenses add distortion and a finite aperture, and both are corrections to this, not replacements for it.

Learn it

• Taught in U11.1 The pinhole camera Vision, University

Used in

• 7.5 Ball physics
• 9.6 Sharing what you see
• U11.2 Intrinsics and calibration

All glossary terms