Trevor Bell, Roger Hilton, Terry Frost, Patrick Heron, Peter Lanyon and others in the group. On moving to London in 1957, Kidner was introduced to The New American Painting exhibition at the Tate Gallery where he saw the Abstract Expressionism of Jackson Pollock, and Willem de Kooning. Somewhat later Kidner was particularly influenced by Mark Rothko's Colour field paintings. These inspired his After Image paintings, sculptures and reliefs, executed between 1957 and 1962. Another defining experience was a course in 1959 run by Victor Pasmore and Harry Thubron which alerted him to the Bauhaus derived ideas of colour. This led him towards a more objective use of colour that stimulated a new, radical approach to his painting. Kidner's first solo exhibition was held at St Hilda's college, Oxford in 1959 where he showed his After Image paintings. However it was not until 1965 that he became recognised as a pioneer of Op Art following the publicity surrounding the exhibition called The Responsive Eye organised by William Seitz at the Museum of Modern Art in New York. Both Kidner and Bridget Riley's work were included. Kidner was to teach at numerous art schools, including Bath Academy of Art and Chelsea College of Art. In 1978 he was invited by the artist Stass Paraskos to be an artist-in-residence at the Cyprus College of Art arts centre in Paphos on the island of Cyprus. Mature career After Image 1959 Kidner said that "Optics presents a challenge that was once offered by perspective". He was referring to the examination of visual perception in the science of linear perspective developed by Leon Battista Alberti and other Renaissance artists in the 15th century. Kidner was also interested in the work of Seurat and the Neo Impressionists who had investigated the connection between the retina and the brain regarding colour perception, as seen in their Pointillist paintings. Rothko's Colour Field abstractions led Kidner to see colour as "pure sensation". For example, in his Moving Green 1959 the colours seem to float in an atmospheric colour relief in front of the canvas.On gazing at the colour field, the eye moves from the green to the red area and a bright, red spot or after image produced by the retina appears in the field. Later Kidner's After Image works became hard edged with flat uniform patterns, when he realised that optical activity producing shimmer is decreased by brushy paintwork