High Quality Content by WIKIPEDIA articles! Walter Percy Day O.B.E.(1878, Luton –1965, Los Angeles) was a British painter best remembered for his work as a matte artist and special effects technician in the film industry. Professional names include W. Percy Day; Percy Day; “Pop” or “Poppa” Day, owing to his collaboration with sons Arthur George Day (1909–1952) draughtsman, Thomas Sydney Day (1912–1985), stills photographer and cameraman, and stepson, Peter Ellenshaw, who also worked in this field.