Nowadays, all movies use special effects, whether it's to add a tiny detail or turn a world of make believe into something credible.
From scenery to imaginary creatures, most are obvious - dragons, surreal landscapes, super human powers... And then there are CGI effects so subtle that even the beadiest of eyes would have a hard time spotting them.
Here are 11 special effects from famous movies that we bet you didn't notice!
1. Blood Diamond, 2006
Jennifer Connelly must have had problems shedding a tear when on the phone to her dying friend, as the special effects team added a computer generated one that trickled down her cheek. No one told Jennifer - perhaps they didn't want to undermine her confidence - and she only found out when the movie premiered.
2. Forrest Gump, 1994
We all know that Forrest Gump has lots of special effects. For example the feather that falls at Tom Hank's feet looks real enough, but was in fact computer generated. Ditto for the ping pong scene! No real ping pong balls were used - Tom Hanks was given a racket and had to pretend to play. The ping pong balls were later added to the scene.
3. Die Hard with a Vengeance, 1995
Bruce Willis didn't wear a sandwich board with these words during the Harlem scene - and for obvious reasons! He actually wore a blank board and the words were later added. Even so, once the movie was released, the sign was considered too insulting for TV audiences, so the team came up with a less controversial 'I hate everybody' version.
4. Black Swan, 2010
Another movie littered with special effects, notably during the scenes where Nina Savers, played by Natalie Portman, suffers from hallucinations. Some, however, are less obvious. For example, when the actress transforms in to the Black Swan and pulls a black feather out of her shoulder - a snippet that was entirely computer generated. Another subtle effect involved changing Natalie's hands, which the director considered to be too small and soft. As a result, her hands were elongated and wrinkles added.
5. A Beautiful Mind 2001
Sometimes directors use special effects in order to protect their cast. In this case it was because Russell Crowe was never going to drown a real baby! In the end, two scenes were shot, the first showing a full bath and the second featuring a baby in an empty bath. The two were then merged to create this deeply disturbing, highly convincing scene.
6. The Wolf of Wall Street, 2013
This movie is visually stunning - a luxury manor, a stunning wedding scene, breathtaking views... But believe it or not, the crew didn't travel around the world to shoot scenes in exotic locations! Most were computer generated, which helped keep the movie within its budget. That said, the scene where the lion strolls through the office is real! But it took several takes - one with the lion on its own, one with the cast and a third just showing the setting. The takes were later merged, with realistic results.
7. Dark Shadows, 2012
Tim Burton's known for being a perfectionist who loves special effects. He wanted Johnny Depp's vampire to look as convincing as possible and his creative team came up with the goods, notably by removing Depp's blinks to give him a terrifying, bloodthirsty stare.
8. Brokeback Mountain, 2005
Scenes involving animals can be particularly tricky, as Ang Lee, the director of Brokeback Mountain, found out. The sheep scene relied on CGI technology to turn the 700 available sheep into a herd of 2,500!
9. Birdman, 2014
Birdman gives the impression that it was shot in one extended take - a real test for the crew who had to deal with numerous issues such as getting the lighting right or matching camera movements and speed... A hardware filter was therefore used to hide cuts for an ingenious seamless finish.
10. The Social Network, 2010
You may not know that the Winklevoss brothers were played by the same actor, Armie Hammer. David Finch was determined that Armie would play both parts and didn't bother to audition any identical twins. So advanced CGI technology was used to replicate the actor's movements and facial expressions, which were then added on once filming finished, giving the impression that genuine identical twins were used.
11. Captain America: The First Avenger, 2011
Chris Evans is a muscular dude and was therefore not physically suitable for the skinnier Steve Rodgers. At first a body double was used, but the idea was later ditched as Steve Rodger's movements didn't look natural. The solution was to use special effects to slim down the actor. This involved shooting each scene from 4 different angles, alongside shrinking Evans's legs so that they looked slim in comparison to other characters in the movie.
Photo credit: Marvel Studios