Geometry of Image Formation

Pinhole camera

The focal length is the distance from the pinhole to the image plane. The size of the projected image (x,y)(x,y) is related by the focal length ff and the distance to the pinhole ZZ.

x=fXZx = f\frac{X}{Z}

y=fYZy = f\frac{Y}{Z}

Rays captured by a lens converge on a focal plane. The distance from the lens to the image plane is twice the distance from the lens to the focal plane.

References

Image formation - Wikipedia