Letters

Leonardo, Vol. 16, No. 4, pp. 333-335, 1983. Printed in Great Britain. LETTERS 0024-094X/83 $3.00 + 0.00 Pergamon Press Ltd. Readers' comments are welcomed on texts published in Leonardo. The Editors reserve the right to shorten letters. Letters should be written in English. OBITUARY: ALBERT GARRETT Albert Garrett, the painter and wood engraver, died suddenly in London on 7 February 1983. He studied art at Camberwell School of Art, The Anglo-French Art Center, and The Slade, London. He was a senior lecturer at the Polytechnic of North London School of Architecture until 1980. An authority on wood engraving, he became President of the Society of Wood Engravers. His work is widely exhibited in museums around the world. Garrett published a number of works, including A History ofBritish Wood Engraving and British Wood Engravings ofthe Twentieth Century. His research on color in motion led to publication in the journal Automobile Engineer of a number of his recommendations on ways to enhance the visibility of moving automobiles. In Leonardo he published On the Effects of Flashing White and Coloured Lights on Humans (Leonardo 9, 213, 1976), detailing some unexpected effects of contemporary art works. An ardent supporter of Leonardo, he recently wrote, "Leonardo has crystallized and fostered the concept of the interrelationship of art, science and technology, which is an aim of many artists, in many countries, who were trained after the holocaust of the Second World War. Leonardo has proven that archival writing and documentation in art can be done. Leading artists and scientists are now actually in dialogue." The art-science-technology community has lost an important member. Roger F. Malina Executive Editor Leonardo FLAT SPHERE AND TETRACONIC PERSPECTIVE Fernando Casas (Leonardo 16, I, 1983) arrives at "flat sphere perspective" by piercing the sphere of vision at a single point, which is topologically stretched to become the bounding circle of the image. This has the unwelcome consequence he mentions, that neighbourhood relations are disturbed in the neighbourhood of the point pierced: points that are very close on the sphere of vision arrive at opposite sides of the circular perspective image. However, it has an advantage he does not mention, that simple mathematical procedures can be used to create the perspective schema. The azimuthal equidistant projection, as used in cartography, provides the rules by which the topological stretching of the sphere can be made precise. Although in most atlases these rules are used to generate two separate hemispheric images, either hemisphere can be extended to represent the whole sphere by simple continuation of these rules. My own "tetraconic perspective" (Leonardo 9, 289, 1976) mentioned in the concluding editor's note to Casas's article, pierces the sphere at four points. This has the welcome consequence that neighbourhood relations are less disturbed. Provided the rotations described on p. 291 are carried out, any given point in the representation can be surrounded by its proper neighbours (although duplicate images ofthese neighbours are also generated in an infinitely repeating image plane). However, tetraconic perspective has the unwelcome consequence that no exact mathematical procedures are immediately evident to generate a perspective image with the desired smoothness. What is wanted is a formulation that blends the procedures of conical projection (which would be applied purely at the four pierced points), azimuthal projection (which would be applied purely at their four antipodes), and cylindrical projection (which would be applied purely at points midway between any two of the previously mentioned points). Can any reader 333 give mathematical form to this hybrid? Meantime I look forward to Casas's promised article on "polar perspective". Kenneth R, Adams Saint Martin's School of Art, 107 Charing Cross Road, London WC2H ODU, U.K. COMMENT: OLD PERSPECTIVE AND NEW VISION In his article, Old Perspective and New Vision, (Leonardo 15, 269, 1982) Georges Coppel claims to be able to determine the proper hanging height and viewing distance of Mantegna's Dead Christ, namely, with the top 1.83 m from the ground and the observer 1.80 m from the picture. It is hard to see on what evidence these assertions are made. Since the space in the foreground of Mantegna's picture is nearly...