I have always wondered how they make those movies in which the same actor plays two different roles(one I saw had the same actor play 8!)? Well yes it is obviously some photography/editing/mixing techniques but I was wondering if someone here knew more details of how it is done. Like how do they manage to show the same actor shaking hands with himself or talking to himself in the same location?
Well one method for a conversation is really quite simple.
Imagin yourselfs have a talk sitting at a table.
wiser is wearing a white outfit and now is wearing a blue outfit.
I’m the director/camerman.
I’ll film wiser’s half of the conversation first. I’ll have a double, someone who looks a little like now sit in now’s spot, wearing now’s outfit. This person only has to look like now in the back of the head. So someone with the same hair color and style will do. I can point the camera over the double’s shoulder, keeping a little bit of the double’s head and shoulder in the shot but it looks straight at wiser.
Then film now’s half of the conversation do the same thing with the double filling in for wiser and wearing wiser’s clothes.
Edit it together and bingo! **Wiser and Now ** are sitting opposit each other.
The real trick is the actor must have both performances in their head and be able to react to a performance that isn’t happening.
Or they could do it like some of the scenes in Terminator II and BTVS where they use the identical twin of the actor to play the second part.
But that’s kind of rare.
Nowadays with digital compositing, it’s a cinch (relatively speaking) to film actors A and B shaking hands and give Actor B Actor A’s face. In bygone days, if they had to film two actors at once so that both their faces were visible, they would lock the camera down, film the actor as Character A, then film him as Character B from the same setup, then matte the two shots together in the cutting room. Shots of two characters touching is often done by shooting tight and using substitute limbs. Watch the Star Trek: Next Generation episode where Data meets his “father” Noonian Soong, both played by Brent Spiner. There’s a tight two-shot where Soong cups Data’s face in his hands; the hands coming from the bottom of the frame are not Spiner’s.
One of the earliest movies I remember which used this technique was the original “Parent Trap” with Hayley Mills. This was way before the days of CGI and special effects as we know them now. I don’t think they even had blue screen in those days. It worked out pretty well, considering what they had to work with.
Buster Keaton played almost every part in “The Playhouse” (1921), there’s an orchestra scene where he’s about 9 people onscreen in one shot. You can get it on DVD from Kino Video.
In older films you’ll notice that the “doubles” don’t move in front of each other. They’d film by figuring out which character would occupy which part of the frame, then lock down the camera, mask the lens so that only the part of the frame with “character A” would be seen, film it, rewind the film, move the mask so that the part of the frame with “character B” would be seen, film it, repeat as necessary. You’re just exposing a part of the film each time. The final product looks like everybody was onstage at once.
More recently you can see other tricks being pulled. Watch “Back To The Future 2” and look closely at how Biff interacts with himself. You can see props that are actually animated, mechanical arms used to move a prop so that it looks like he hands himself something, etc.
Buster Keaton used the technique in “The Playhouse” in 1921, which is triply impressive for two reasons: he portrayed an entire movie audience, and cameras those days were hand cranked.
The technique in silent days was simple:
- Put a mask over one half of the lens. This keeps the film on that side from being exposed.
- Film the actor.
- Rewind the film in the camera.
- Put the mask over the other half of the lens.
- Film the actor again.
Presto – he’s acting with himself.
In “The Playhouse,” they used a special mask for each version of Keaton in the audience. They’d open one part of it, film him, rewind, open another, etc.
Hand cranked! 
The technique was used in Hollywood for years. Often you could spot a vertical object – a bar or a design – to separate the two shots. You’ll notice that the two versions of the actors don’t touch each other and are usually are well apart from each other.
Patty Duke used both this technique and the cheaper “over the shoulder” shot.
I can’t recall the name of the film but Gene Kelly has a fantastic sequence where he dances with himself. It’s a fairly long shot with the camera moving. And this was before computer/motion controlled cameras.