7 NOVEMBER 1987, Page 24

Do it yourself

Sir: Giles Auty is right when he suggests (Exhibitions, 10 October) that art histo- rians should try their hand at painting. So often their assessments are awry because they are ignorant of the practicalities of the craft — for instance, I guess that very few of them could demonstrate why the per- spective in the majority of Canaletto's pictures is visually wrong.

They can also often go adrift over portraiture; the art historian writing the notes for the current Acquisition in Focus exhibition at the National Gallery points out that in the David self-portrait 'the artist glares at the spectator with an ardent expression. It difficult not to associate this feeling of urgency with David's in- creasing involvement with the Revolution.' Well, hardly. David's expression is that of all self-portraitists who rely on a single mirror; concentrated observation of their own face is the reason why the eyes are like that. First and foremost, painters of natur- alistic portraits are not burrowing after some internal, hidden 'character' — what they are trying to do is get the length of the nose right.

William Hewison

S Southdown Drive, London SW20