1. A method of measuring a shape of a specular reflective surface, the method comprising: producing a reflection of a pattern displayed on a surface of a target positioned at a target plane from a specular reflective surface positioned at a measurement plane; recording an image of the reflection at an imaging plane; determining positions of a plurality of points on the specular reflective surface relative to the imaging plane; determining a first relation between feature positions on the image of the reflection and feature positions on the pattern; and determining the shape of the specular reflective surface from a second relation involving a surface profile of the specular reflective surface and the first relation using the positions of the plurality of points as an initial condition.