Cameron said he plans to complete principal shooting on the three movies at one time, perhaps over a period of about nine months and beginning in 2015. He said the aim is to release the first sequel in time for Christmas 2016 and the following sequels in late 2017 and late 2018."It's quite a thrill to be officially saying that we're bringing the Avatar films to New Zealand," he told a press conference. "We had such a wonderful experience here making the first film."Cameron said work has already begun on the writing and design of the movies.New Zealand's government has agreed to a 25 percent rebate for the films, meaning it will pick up one-quarter of the tab. The agreement states that Lightstorm and Twentieth Century Fox will spend at least $413 million in New Zealand on the movies.As is typical with blockbusters, Cameron declined to disclose a budget. But he did say he expects that economies of scale will help the three movies together cost less than $1 billion.He said that he intends to make the movies in 3D and to shoot at least some sequences at 48 frames per second.Films are typically shot in 24 frames per second.