http://www.google.co.uk/imgres?imgurl=http://static.bbc.co.uk/programmeimages/640x360/clip/p00ndbjt.jpg%3Fnodefault%3Dtrue&imgrefurl=http://www.bbc.co.uk/programmes/p00ndbjt&usg=__l5UFZ-Kr8wICAoWlkGPynO6LTEY=&h=360&w=640&sz=77&hl=en&start=2&zoom=1&tbnid=9jTgFrNkoTAFdM:&tbnh=77&tbnw=137&ei=yMF6T7GOGsu98gPhw6i2CA&prev=/images%3Fq%3Dstout%2Bman%2Bwith%2Ba%2Bjug%2Bevan%2Bwalters%26um%3D1%26hl%3Den%26gbv%3D2%26tbm%3Disch&um=1&itbs=1

http://www.google.co.uk/imgres?imgurl=http://www.lumen.nu/rekveld/wp/wp-content/uploads/2007/03/dioptrique034.jpg&imgrefurl=http://www.lumen.nu/rekveld/wp/%3Fp%3D352&usg=__y4L-EC4fL91xdqMyMiMey-x94W8=&h=534&w=279&sz=27&hl=en&start=4&zoom=1&tbnid=MFTACHqnl8McOM:&tbnh=132&tbnw=69&ei=7s56T_mpN9Dm8QOpmJiyCA&prev=/search%3Fq%3Ddescartes%2Beye%26um%3D1%26hl%3Den%26sa%3DN%26gbv%3D2%26tbm%3Disch&um=1&itbs=1

On Hockney photocollages:
http://www.natures-pencil.com/heroes/hockney.htm