I wasn’t aware of the full extent of the controversy about David Hockney’s theories. Fortunately, Luke Strosnider emailed me to fill me in. The other day, I had posted the entry

“Computer analysis of a 17th century painting shows that the artist did not, as has been claimed, use optical devices to project a perfect image of the scene onto his canvas. The researcher behind the analysis believes his findings undermine many aspects of a theory recently put forward by the painter David Hockney.” - story

You can find more background about this on a page of resources in Believer Magazine. The current edition of the magazine also features (or more accurately: reproduces) a six-page hand-written fax that Hockney sent to the New York Times (which, following the shoddy journalistic behaviour they have been showing lately, they didn’t publish). As Luke writes “in the fax, hockney very eloquently refutes the idea that his theory is in need of being proven/discredited. instead, he seems to think the emphasis is more on getting people to relate to the history of image-making as a history of optics. he also brings up many other fascinating points - it’s riveting.”
(thanks, Luke!)