Both aim to champion creativity and experimentation within short form documentary.
During 2016, the Fund will award 12 grants of up to £5,000 to filmmakers with untold stories and will also provide those films with a home on the Postcards platform.
Three films will be green-lit at Sheffield Doc/Fest in June 2016 and the remaining will be commissioned over the course of the year from online submissions.
The deadline for the 1st round of submissions is 31st January 2016.
The Postcards dedicated site - postcards.justsolondon.com - has also launched.
Currently it offers six shorts: Five Stone of Lead, Aka Chan, Funabashi Dreams, Rocket Wars, Stopping Time and Soft Serve.
The films, or ‘Postcards’, cover true life subjects ranging from a century old rocket-launching tradition on a Greek island to the next generation of Japan's martial artists
Just So, which is also behind the successful international music platform, Black Cab Sessions, said "the platform will not only provide filmmakers with the opportunity to make films but also to get them seen on a dedicated online platform in partnership with one of the key global voices in documentary, Sheffield Doc/Fest."