I've read Hockney's book, and it is completely convincing to anyone who (to paraphrase P. G. Wodehouse) isn't being paid to be unconvinced by it. In his book he

I've read Hockney's book, and it is completely convincing to anyone who (to paraphrase P. G. Wodehouse) isn't being paid to be unconvinced by it. In his book he finds geometric errors (mismatches in the textures and folds of tablecloths and floors, for example) and depth of field artifacts exactly where you'd expect to find them if the painter were using optics to focus images onto a drawing canvas, and had to change focus as he moved out of focus planes. He also points out that Caravaggio's greatest paintings (among many examples) are a combination of astonishingly deft lighting and detail combined with gross errors that you'd get if (essentially) copying and pasting bits of photographs onto a canvas. (And, hey, I love Caravaggio...) The critics would have you believe that Caravaggio was a godlike draftsman who cold realistically paint the veins on people's eyelids but couldn't put their arms in the right position with respect to their bodies. These guys invented (analog) Photoshop in the 17th century and it was one of their trade secrets. Apparently art critics find this insufficiently awesome, or the wrong kind of awesome. (Think: science awesome vs. romantic artiste awesome.) Hockney also traces the passing of the secret technique by putting the works of various artists on an up-down (geographic) and left-right (time) chart and can show how two artists (one of whom had godlike drafting abilities and the other of whom was merely competent) crossed paths and then suddenly the lesser artist became godlike. The argument that Hockney is just jealous of the talent of the old masters is equally ridiculous when he shows his own work with and without the techniques. One could level the charges that the art "authorities" that disbelieve him are simply jealous of their own utter lack of talent. tl;dr -- most "art experts" are self-deluded idiots. News at 11.