From a welling tear to a wounded stare, the ability to project convincing emotions in close-up is the test of a cinema actor. But now it appears that there is more to some star turns than meets the audience’s eye.

Directors have started to manipulate actors’ performances in postproduction.

Modern visual effects technology allows them to go beyond traditional cosmetic changes, such as removing wrinkles and unsightly hairs, and adjust actors facial expressions and subtly alter the mood of a scene.

At the Visual Effects Society’s recent conference, Jeff Okun, the organisation’s chairman, showed before and after versions of one of the climactic shots in the Oscar-nominated film Blood Diamond.

In the “before” shot Jennifer Connolly, the leading lady, was shown talking on her mobile phone. The digitally manipulated “after” shot showed her talking on her mobile phone with a tear rolling down her cheek. Such alterations are becoming increasingly common, but practitioners are discouraged from discussing this work.

“Acting is all about honesty, but something like this makes what you see on screen a dishonest moment,” said a leading technician. “Everyone feels a bit dirty about it.”

Visual effects experts privately admit to changing actors’ expressions: opening or closing eyes; making a limp more convincing; removing breathing signs; eradicating blinking eyelids from a lingering gaze; or splicing together different takes of an unsuccessful love scene to produce one in which both parties look like they are enjoying themselves.

Mr Okun told The Times: “What used to cost £40,000 is now only going to cost you £6,000. It’s cheaper than reshooting a scene. We are put in a difficult moral position when directors ask us to change an actor’s performance. The performance is sacrosanct and to alter it is creepy. But we don’t get hired by actors. We get hired by directors.”

One veteran effects man said: “Most of the time, the changes are asked for by directors who don’t know what they are doing. The sort who in post production go, ‘Oh, now I see what I should have done.’ ” Actors are understandably concerned. According to Variety, the leading industry publication, a proposal to give actors approval of digital alterations was first put forward in negotiations with the Alliance of Motion Picture and Television Producers in 1998. Tom Le Grua, of the Screen Actors Guild, told the magazine: “The proposal said no part of a performance may be altered digitally or otherwise without the performer’s consent.” It was rejected and has languished since in committee discussions.

Some actors such as Tom Cruise have begun to write clauses into their contracts granting them full control of their own digital assets, Mr Okun said. “They are saying: if you make me look better, then it’s fine. But if you are dealing with the subtleties of a dramatic performance it’s not fine.”

However, Matt Johnson, a visual effects supervisor at Cinesite in Soho, London, who worked on King Arthur and V for Vendetta, said: “Actors have always known that directors would manipulate their performances [by clever editing in postproduction]. Now they are realising that visual effects can give directors even more choice. But I think it would be quite challenging to take a performance that wasn’t working at all and completely revolutionise it digitally. Audiences would be able to spot that.”

New scenes

Westworld (1973) showed a pixellated view of what the world looked like to one of the robot characters. In the sequel Futureworld (1977) the actor Peter Fonda was cloned In

Forrest Gump, the removal of Gary Sinise’s legs was so successful that fans think he is an amputee

Oliver Reed died of a heart attack during the filming of Gladiator. Some scenes were reshot posthumously, with Reed’s face superimposed on to a double

Source: Times database

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