For the past six months, Sony has been giving free masterclasses in 3D to around 500 professional movie-makers. The first series was in Hollywood, but for the past two weeks, Sony took over two studios at the BBC TV Centre.

The driving force is Buzz Hayes, chief instructor at the Sony 3D technology centre at Sony Pictures in Los Angeles.

Mr Hayes tackled several topics of interest to dealers, such as possible health issues. This first reared its head when – to play legally safe – Samsung issued health warnings with its 3D TVs.

"I spoke with Lenny Lipton, who has been in 3D film-making for years and started RealD (the system used in most cinemas)," said Mr Hayes. "I said if there were going to be a health issues, we should know about it now. Lenny said that in all his years of working with 3D, and with professionals who spend all their time looking at 3D screens, he had never encountered a single health issue."

But there are mistakes that film-makers can make that will definitely upset viewers. Such as shooting on a boat in rough seas and making people seasick. Or strapping a camera to a bike and riding it down a dirt track.

There could be a lot of queasy viewers once Panasonic's 3D consumer camcorder hits the high street.

The same thing can happen if there is extreme depth which makes the viewer's eyes diverge – look out and sideways – whereas eyes normally converge to look inwards.

"I warn you this will hurt like heck," said Mr Hayes, before screening a test that showed objects at wildly different depths apart.

He also challenged a few 3D assumptions.

"People say you can't do fast cuts in 3D. But that's wrong. You can as long as there are no wildly different depths that make the eye's convergence keep changing."

As for the glasses/no glasses debate, he added: “People talk about waiting for no-glasses auto-stereo. But for that we are going to need four times HD resolution. If you create nine views, that reduces resolution to a ninth or tenth. You end up with images like emailed photos. Good auto-stereo may need up to 27 views."

So 3D with no glasses is a long way off.

Barry Fox