The new six-month project, called The Search, is similar to its mobileAct Unsigned competition for new bands, which it is running with Orange around its music-orientated Walkman devices.
The photography promotion splits the entries into categories, with monthly prizes for each category winner. Celebrity photographers will also set challenges.
Monthly category winners will go head-to-head for the title of Cameraphone Photographer of the Year, and entry into Sony Ericssons global competition.
A gallery exhibition of the best entries will also be staged. Cameraphone users can upload images to the Sony Ericsson website.
Sony Ericsson UK and Ireland managing director John Harber said: The cameraphone is spearheading a photographic revolution.
The K810i features a 3.2-megapixel camera and is on sale already. The HSDPA-enabled K850i has a five-megapixel camera and launches later this year.
As an extra promotional tool, Sony Ericsson has counted public votes on the most iconic photographs of the past 30 years.
Images of the terrorist attacks on the World Trade Center in New York, the 1982 Falklands War and Diego Maradonas hand of god goal against England in the 1986 World Cup all ranked highly.