My article for FoMRHI, the Fellowship of Makers and Researchers of Historic Instruments.  about the use of mirrors and lenses by artists from 1420 and the implications for modern instrument makers when interpreting and copying paintings of musical instruments.

David Hockney carried out research at the very end of the 1990's into certain painting techniques used by many of the 'Old Masters'. I have no idea if this is widely known by instrument makers and researchers. It culminated in a lavish book published in 2001 entitled Secret Knowledge- Rediscovering the lost techniques of the Old Masters. I was first made aware of his research through a fascinating TV program that he made, which fortunately I videoed and have watched many times. I have heard some hearsay that it caused a bit of a stir among art historians. I do not know whether this stir was of the “We- knew-about- this- all- the- time” or “Hockney- is- talking- a- load- of- rubbish” variety. But I do know that anyone who has ever been involved in interpreting the evidence of musical instruments painted by the Old Masters should read this book.

 An enormous advance in realistic painting took place around 1430- 1440. This has long been noted by art historians but it has never has been properly explained. Hockney gives a very clear case that from this period onwards many of' the Old Masters were using convex mirrors to project the image onto the canvas.

If you already find yourself sceptical about this I really encourage you to read his book as the evidence is compelling. It certainly has changed the way I view paintings from this era. Now it becomes clear why so many old Flemish portrait paintings measure about one foot square. This is the optimum size for a projected image using a concave mirror. Most of us will be familiar with early portraits where the background is very dark, yet there is bright light on one side of the subjects face. And the irises of the subject are contracted. The subject would have been sitting in full sunshine and the artist would be painting in a darkened area using the image projected by a concave mirror

The next big advance came around 1510 when there had been significant advances in glass making which allowed lens maker to supply artists with lenses that they could use for this purpose.

Long before I knew anything about Hockney's research I enlarged to life size the Albrecht Dürer woodcut of a bagpiper and mounted it on plywood- it stands about 5 foot high. I usually take it to The London Early Music Exhibition to jolly up my stall.

 The original woodcut is post card sized and yet when I had it enlarged all the proportions of the bagpiper still remained absolutely correct. I often mused that it seemed to have a 'photographic look' and marvelled at Dürer's skill to draw such a small figure with perfect proportions. He made that print in 1514, which is only four years after lenses started to be used by artists.

 A lens reverses the image it projects. A clue that Dürer used a lens for this print is that the image is 'back to front'. The piper is 'left handed'. And, yes, it is quite possible that he actually was a 'left handed' piper. But you try looking at any paintings of musicians and see how many of them suddenly become left handed after 1510!

 Working in conjunction with an optical scientist Hockney gives a detailed analysis

 of some of the inevitable distortions that appear when an artist tries to fit several projections together into a complete painting. He shows various 'clues' one can look for.

 Once one can spot these 'clues' and can be confident that the artist has painted using this technique one can have much more confidence in the dimensions of a musical instrument in a painting.

 Secret Knowledge- Rediscovering the lost techniques of the Old Masters. David Hockney (Thames & Hudson ) 2001 ISMN 0-500-23785-9

Julian Goodacre