Farm field with rows of plastic sheet and tractor.

“Bridget Louise Riley (born 24 April 1931 in Norwood, London) is an English painter who is one of the foremost proponents of op art.” http://en.wikipedia.org/wiki/Bridget_Riley

“Bridget Riley is a well-known British artist celebrated since the mid-1960s for her distinctive, optically vibrant paintings, called “Op Art.” She explores optical phenomena and juxtaposes color either by using a chromatic technique of identifiable hues or by selecting achromatic colors (black, white or gray). In doing so, her work appears to flicker, pulsate and move, encouraging the viewer’s visual tension. Riley’s vibrant optical pattern paintings, which she painted in the 1960s, were hugely popular and become a hallmark of the period.”
http://www.webexhibits.org/colorart/riley.html
(Color Vision and Art is one of several exhibits in the WebExhibits online museum, all of which promote discovery through multidisciplinary approaches that support all learning styles. WebExhibits is a public service of the Institute for Dynamic Educational Advancement.)
Op art, also known as optical art, is a style[1] of visual art that makes use of optical illusions.
"Optical art is a method of painting concerning the interaction between illusion and picture plane, between understanding and seeing." Op art works are abstract, with many of the better known pieces made in only black and white. When the viewer looks at them, the impression is given of movement, hidden images, flashing and vibration, patterns, or alternatively, of swelling or warping.” http://en.wikipedia.org/wiki/Op_art
I was out taking photos today and coming down a mountain road I stopped at a scenic overlook. Below me were huge spring fields having just been planted with crops. The fields had been covered with rolls of sheet plastic to keep down weeds. The expanse was fantastic as it created linear patterns that are visually very much like op art in their optical vibrations. If you look close you can see a tractor sitting in the middle of this found op art field.
http://facweb.cs.depaul.edu/sgrais/images/Line/10_vv_bridget_riley_1967det.gif

http://gilbertgarage.files.wordpress.com/2010/10/bridget-riley_1296818c.jpg

Check this out. Prince William listens to artist Bridget Riley in front of "Cataract 3"

http://www.rca.ac.uk/UploadedImages/BRIDGET%20RILEY.jpg

http://www.cac.lt/files/images/914696/2004_Bridget_Riley_1_400x386.jpg

http://www.harpersbazaar.co.uk/cm/harpersbazaaruk/images/ob/WDY-Bridget_Riley-NPG2.jpg