The pinhole camera is the most common camera model in Computer Vision.

We represent a pinhole camera by a plane called retinian plane
and a point *C* called optical center. Let *M* be a 3D point with the
coordinates (*X* *Y* *Z* *T*)^{t} in the projective space .In figure 1 we show how we project the
point *M* in *m* ( *T u*, *T v*,*T*), its image on the retinian plane
. The formula 1 gives us the relation
between *M* and *m*, *P* being the projection matrix. The projection
matrix *P* can be decomposed into a product of three matrixes as we show
in formula 2.

(1) |

(2) |

where:

- , the 3D coordinates change matrix:
(3) -
*P*, the standard projection :_{0}(4) -
*A*, the 2D coordinates change matrix:(5)

The parameters of (i.e. *r*_{x},*r*_{y},*r*_{z},*t*_{x},*t*_{y},*t*_{z}) are
called the extrinsic parameters and the parameters of *A* (i.e.
) are called the intrinsic
parameters. The parameter (the angle between the rows and columns of the camera) is usually set to [Vai90].