This is an advert for something you can’t see, unless it’s repeated on BBC4 some time this week, if you can get BBC4….. (I checked BBC iplayer and youtube, to no avail.)

I know that the thought of a documentary about art might not strike you as utterly compelling, but that’s what it was – both “compelling” and a “documentary about art”.

It was an old Omnibus programme made by David Hockney. He argued that optical instruments and techniques had been used in Renaissance art, making it possible for the artists to produce accurate perspective and photorealistic effects. (According to Hockney, van Eyck, used camera obscura techniques, Caravaggio used mirror projections, and so on.)

This viewpoint has been pretty much discredited by many art critics and scientists. That’s not really the point, though.

Hockney’s attempts to recreate the paintings and his great enthusiasm and skill are mesmerising. It’s a real pleasure to watch.