Hans Holbein the Younger, court painter during the reign of Henry VIII, produced some spectacular works. Amongst the most celebrated is a double portrait of Jean de Dinteville, French Ambassador to Henry’s court, and Georges de Selve, Bishop of Lavaur. Painted by Holbein in 1533, the picture, known as The Ambassadors, hangs in the National Gallery, London.
Diagonally across the lower foreground of The Ambassadors there is an elongated form, the significance of which is not immediately obvious. It is a perspective anamorphosis, an intentionally distorted image who’s nature becomes clear when it is viewed from an oblique angle. From a vantage-point to the centre-right of the picture, the form reveals itself to be a skull, probably included as a memento mori.
Visual artists developed the techniques of painting in perspective during the early Renaissance, and mathematicians developed projective geometry, which systematizes the principles of perspective. Holbein had a deep appreciation of these principles, but the precise method that he used to produce the anamorphic form is still a matter of debate.
The picture contains images of books, globes and scientific apparatus, reflecting the learning of the two wealthy and influential subjects. It is approximately life-size, painted in oil on an oak panel, and is close to an exact square in shape. Detailed analysis of the anamorphic form has been done, using a range of complex mathematical transformations. To illustrate the ideas, we will use a computer image processing package (GIMP) to isolate and (un-)distort the anamorphic form.
First, we extract the section of the image in the centre lower foreground:
The three transformations we have performed are a rotation R, a stretching transformation S and an inverse transformation RT
T = RT S R
The three operations are equivalent to a single stretching transformation about an oblique axis. A more precise analysis leads to the following image:
The uses of the technique of anamorphosis are not limited to the fine arts. Advertisers display images flat on a football pitch which, when viewed obliquely through a television camera, appear to be vertically-standing signs, like that shown here:
Peter Lynch’s book about walking around the coastal counties of Ireland is now available as an ebook (at a very low price!). For more information and photographs go to RRI.