Continuous Moving background with changing people

Phil Beastall · March 29, 2010

I have a project coming up and the client wants to have a person walking down the street with a dog. They then want this person to become someone else without the background jumping at all, so a continuous motion. This person will then become someone else, and so on. Considering we will need to see feet, what's the best way to shoot this? Would it need to be on greenscreen on some kind of treadmill? Because I am concerned it might not look great.

Edited March 29, 2010 by Phil Beastall

blackboxpictures · April 4, 2010

I have a project coming up and the client wants to have a person walking down the street with a dog. They then want this person to become someone else without the background jumping at all, so a continuous motion. This person will then become someone else, and so on. Considering we will need to see feet, what's the best way to shoot this? Would it need to be on greenscreen on some kind of treadmill? Because I am concerned it might not look great.

You could do this with good ol' clever shots if you're stuck for a solution. Make every character wear the same shoes and pants, something really generic, or at least the same colour. Then shoot your talent, the multiple people along a street or wall or wherever you are using a long track dolly so you can basically recreate the shots each time.

Then just get footage of the feet, legs and the dog walking. Whenever you need to switch people, just cut to that footage (or similar non-upper-body showing footage) and then cut back. If the dog is the same and they're in the same location then the continuity will be restored.

You could add to the continuity by adding some posters or peeling paint or something noticeable behind them and when you switch between the shots of different talent cut to the same basic point in time so that the recognisable marks carry along as if in a normal dollying shot.

Hope this helps!

Evan Ferrario · April 4, 2010

If you want to do this without heavy post work, it will take a lot of setup and practice.

You will need your camera on a dolly that travels backwards at as constant speed as possible. Then you need marks for the actors and camera when the shot will switch actors. The trick is that you need the camera in the exact same position that the one shot ends as the next one begins and both actors in relatively the same body position. Don't try to stop or start on the mark, you need to maintain the illusion of constant movement so by practicing, you can have actor one walk into the right position when the camera reaches its mark, then repeat the motion with actor two, this time you need the actor to be in the same position as the first actor when they reach the first mark, and then continue past that mark until they reach the next one.

The dolly needs to repeat the exact same movement every time so you probably need a track. Speed needs to constant so whoever is pushing the dolly should practice. The trick to doing this kind of camera trick is getting the actors in the right spot when the camera hits its mark. With a dolly, it is fairly easy in post to find where the two shots can be tied together, you just line up the background. The problem is going to happen when you want to cut to line up the actors movement, not the background. There is only one moment where the backgrounds will line up between the two shots and you will have to cut at this moment.

I tried a quick experiment on a short I was shooting with a similar effect, I wanted a continuous shot through a window. http://www.youtube.com/watch?v=DtEOL97pLws It's certainly not perfect, but even without a dolly, you can see the two shots go together fairly well.

changes in Lightning, background, and speed will give away that the camera shot changed and ruin the illusion of a continuous shot. You also might need a small crop or dissolve as the clip switch. This shot can be done, and it can be done without a lot of cgi or greenscreen, but it will take a lot of practice. I would try to get a dozen good takes of each actor so you have lots of options. If your client is willing to understand and accept the time it will take, go for it. I personally don't think green screen would be easier for this setup and it will never end up looking as real as just doing it.