David Hockney had this idea about Western paintings suddenly taking off in a big way with the use of optical devices as aids to perspective and painting and his claim was that this sort of realism in painting really came from the artist being able to see optical images on screen and they didn’t necessarily copy that screen but the idea that you could get an optical image representing reality was enough to make them think more fully about what it is to represent on a canvas with paint. I think the jury is out actually. It seems to work at about the right time. I think the evidence is that sitters in portraits weren’t actually surrounded by these curved mirrors, they are actually mirrors and not lens as he suggested, because they would have reported it. I mean nobody reported the, you know, the surrounded with apparatus and whatnot, but on the other hand I think he was more certainly right that art is learnt from looking at optical images projected by curved mirrors or lenses. I think this is almost certainly right and it may be that Vermeer actually used what’s called a camera obscura directly. My own guess is it wasn’t so much used directly tracing the image and this sort of thing which is difficult to do. I mean it would have been upside down, it would have been very faint and things like this but what you saw in the optical image gave him an idea of what it is possible to do on a piece of paper or canvas. I personally think that’s it, so I agree with half his thesis but perhaps not the other half. And what about Canalettos with the amazing details of Venice and so on? Yes. Well, this is a difficult question, isn’t it? You either have to say that some painters are amazingly good at painting or you have to say they use a technique which some people might call cheating. And when do you call it cheating and when you don’t is a bit arbitrary, I mean, heavens, there’s nothing wrong with having a rest for one’s wrist when you’re using the brush in a delicate bit of work on the painting but some people think you shouldn’t use a lens. Okay. Why could you use a rest for your arms to stop it wiggling about and not be allowed to use a lens, you know? It’s very arbitrary, I think. I don’t think it’s cheating, I think it’s using your intelligence to help things along a bit.