David McKeran started to make test card paintings based on television test cards in 1991, and has since returned to them many times. He was initially interested in the fact that the colours and patterns were devised for a specific purpose; as a tuning aid for television engineers, and that any transmission or reception problem would manifest itself in a disruption to the visual logic of the image. David liked the testcard's "technical purity and self containment" and the idea of making art from the "art-less". Although the first testcard painting was an accurate copy of an existing television image, subsequent paintings were less faithful, as each image required some "aesthetic tweaking" in order to satisfy the logical sequence of the design, making the final paintings seem visually "correct". The most recent testcards from the "Ambassador" series are based on the Hans Holbein painting of that name in the National Gallery, London. The stretched images give the testcards something of an anamorphic quality akin to the deception experienced when viewing the skull in the foreground of the Holbein painting.