VENICE • Alexander Payne's Downsizing, a satire about shrinking humans to 12.5cm tall as a solution to over-population, opened the Venice Film Festival on Wednesday.

The movie, starring Matt Damon and Kristen Wiig, occupied a curtain-raising slot, which has come to be seen as a launch pad for films with Oscar ambitions, and got effusive reviews.

The Hollywood Reporter said Payne had "hit the creative jackpot", while Variety welcomed a "ticklish and resonant crowd- pleaser for grown ups".

The movie tells the story of a financially strapped occupational therapist (Damon) and his wife (Wiig), who decide to be downsized - a process that is irreversible - so they can be part of an affluent "small community" where money goes a lot further.

Damon said films were the best vehicle to help humans empathise with one another.

Despite its apocalyptic tone, Downsizing ultimately is an optimistic movie, he said.

"At the end of the day, there is the sense that we are all in this together... I feel that is a very hopeful message in what is a very divided world," he told journalists.

While Downsizing is set in America, Payne brings in characters from across the world to show how something like this phenomenon "would ripple around the world", he said.

This is a new foray for the film-maker, whose past features - including Nebraska (2013) and About Schmidt (2002) - primarily focused on America's mid-west.

Downsizing is one of 21 features vying for Venice's Golden Lion, which will be awarded on Sept 9.

The festival has premiered Oscar winners, including La La Land (2016) and Birdman (2014).

REUTERS, AGENCE FRANCE-PRESS