Here’s an example.
In 1986 we were prepping an episode of a TV Series called “Stingray.” The scene in question was of a ship leaving the dock and because of time and budget, we couldn’t afford to shoot a real ship leaving the dock so we had to come up with a creative idea.
We found a location (an old pier) where a cargo ship was permanently docked. After scouting the interior of the ship, we realized it worked for our interiors, but it couldn’t be moved. So how do we film the shop leaving the dock?
Since our cargo ship couldn’t really move, we will “make it leave the dock” by using a camera on a foreground object moving away from the ship in the background. This technique will give the audience the illusion that the ship is departing from the dock – where in reality, it never moved at all.
So this is how we accomplished the shot. We placed a car on a trailer and added a few extras standing by the car. We attached the camera to the trailer (with the car and extras in the foreground) so we could see the cargo ship in the background. Other extras were placed on the ship waving etc. On cue, the trailer was pulled forward as we filmed the extras on the ship waving.
And boy did it work. When we viewed the rushes the next day, the cargo ship “was” leaving port – just like we saw the battleship leaving port in Eisenstein’s movie.