Many in the art establishment are horrified by Hockney's thesis. Some suggest that using lenses would be 'cheating.' However, Hockney responds by stating "...optics don't make drawing any easier either, far from it — I know, I've used them. *** To suggest that artists used optical devices, as I'm doing here, is not to diminish their achievements. For me, it makes them all the more astounding."
This is a large book, nearly 300 pages, with hundreds of color photographs of the western world's great paintings. Many color close-ups are included. At first glance you could easily mistake this for a coffee-table book. But open it up, and it is far more.
Hockney gathers the clues like a lawyer building a case before a jury. He includes visual evidence in the form of the paintings themselves, which he painstakingly dissects.
For instance, he explains why so many of the great paintings depict left-handed people. He claims most likely they were of right-handed people with the image inverted by the use of a mirror.
Hockney also includes documentary evidence, in the form of historical documents where references are made to optics and 'trade secrets' used by the artists.
The end result is a fascinating mystery story. After reading Secret Knowledge, you will never look at a Great Masterpiece the same way.