Yesterday, I saw a very interesting TV-documentary starring David Hockney, who showed the viewers how he believes some old masters at painting used mirrors and optics to create their photo-realistic masterpieces. Here's a link to a page describing a piece of the process with a bit of healthy scepticism thrown in. There's a film and book available about the whole shebang as well.

For instance, Hockney believes van Eyck's "The Arnolfini Marriage" clearly shows the pro's and con's with optics. While the chandelier is beautifully painted, subtle shades can be found in the picture, that suggest aberrations only caused by the use of optics.

Other examples of his belief include Lotto's "Husband and Wife" and van Eycks "Ghent Altarpiece".

Some people do believe Hockney's theories to be too hard to swallow, as in this case. Never the less, it's an interesting exhibition.

I like the part in the documentary, where Hockney and a professor in optics examine a painting and the professor even comes up with the dimensions of the optics used.