We have built some models showing central perspectives of a plane upon a secant plane. We have drawn pencil of rays (parallel or with a centre), triangles, quadrilaters, circles and it is possible to observe the perspectivity properties.Corresponding points are connected by incident rays. If we rotate a plane on the axis, during the motion corresponding points are aligned with the centre only if also the centre rotates; when the planes are superimposed, also the centre lies on the planes. On the superimposed planes there is a geometric transformation called homology. In particular it is possible to see what kind of conics corresponds to a circle in dipendence on the position of the circle .