This need to be always drawing is something he has in common with his idol Picasso. But while he sends out most of his iPad images as gifts he has also produced numerous more elaborate computer-enhanced pictures for exhibition and for sale. I suspect they will never be more than curiosities in his career. Those of the Wolds often look as if Maxfield Parrish had been holidaying in Yorkshire, with hyperreal trees contrasting with primitively rendered swathes of grass or road. "Anyone who likes drawing and mark-making would like to explore new media," Hockney says. This may be true but free-drawing on a computer is still a developing technology and while Hockney may believe that "limitations are really good for you" the evidence doesn't always support him. For all the tactility of swiping fingers or stylus on a screen the results have the off-putting tang of artificiality. 

This though is exactly the point where critics and Hockney diverge, although both are right. It is the role of critics to identify his strengths and weaknesses as an artist and it is his job to follow where his nose takes him. His is essentially an art of externals and this is not necessarily a pejorative judgment. With his Bridlington paintings he returns to certain sites and paints them over and over again — the same trees ("the largest manifestation of the life force we see") with or without leaves, in summer and winter, in bright sunlight and under slab-grey skies. Monet did the same with his pictures of Rouen Cathedral and of haystacks. Hockney doesn't attach a message to the pictures or claim that they are anything other than a visual record of seasonal change. If the pictures have an emotional charge then that is supplementary.

What upset people when he suggested that Vermeer, for example, relied heavily for his pictures on the images projected by a camera obscura was that he seemed to be suggesting that mechanics were more important than creativity in making art. His point, however, was that profound expression needs technique and artists should use whatever means necessary to hone the way they see. His own restless experimentation with technology may simply be an admission that he hasn't yet found the perfect medium for himself.