A 3D version of the latest Bourne movie made exclusively for Chinese cinemas has caused local audiences to complain about headaches and nausea.

The format remains hugely popular in the country, particularly when it comes to action movies. But the conversion process required to give the 2D-shot film an extra dimension seems to have been ill-judged in this case.

Why has China got a 3D Bourne?

Cinemas usually charge more for movies screened in three dimensions, so there's an obvious incentive to show them in the format.But while Europe and the US have seen ticket sales for 3D movies decline, there's still a strong appetite for the technology in China.

Many theatres in the country are fairly new and have equipped themselves with the latest projectors.When it comes to 3D movies, however, there are two kinds.

"Real" 3D movies are shot with a dual-lens cameras, which capture two versions of every shot. Special glasses let viewers see a different one with each eye. Many critics believe this delivers the best illusion of depth.But another, cheaper option is to film in 2D and then simulate the effect in post production by using computers.

While this can work well for some movies, it does not for others, with Jason Bourne being a case in point.Its director Paul Greengrass shot several sequences using a handheld camera and then made rapid cuts to create a fast-paced, hectic edit.

It appears that converting this into 3D has made the film hard to watch, and has caused audiences to feel nauseous.

Why not watch in 2D?

Normally, Chinese cinemas offer audiences a choice.But in the case of Matt Damon's new movie, the vast majority opted only to show it in 3D in its opening week.

Out of 149 cinemas in Beijing, only eight are currently showing the 2D version, according to local media.In Shanghai, it's said to be only nine out of 174.

Movie-goers have complained about this on social media, with some claiming it's an attempt to force them to pay premium prices.Following the backlash, Universal Picture says it now aims to add more 2D screenings.