How to best combine slowmo background with regular speed foreground?

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davide

Well-known member
Hey guys,

I'm planning out the shots for a film I'll be shooting in August and I was wondering if I could get your advice for a specific scene. There's a scene in the film where the main character is walking out of a hospital after receiving some bad news. I want to be able to have him walk off camera at regular speed (24fps) while the frame rate for everything else (extras walking, cars driving past) is ramped up to around 48fps. What is the best way to acheive something like this?

The camera we'll be using will most likely be the Canon XLA1 and I'll be editing on Final Cut Pro. My initial guess would be involving a green screen. I'd shoot the hospital exterior at 60i. Then shoot the main character walking in front of the screen at 24f. Is there a better way to do this? Or if my idea is close to being right any advice on how to make it work? Also, is there a good way of doing a ramp in post or would I have to have the background in slowmo for the entire shot rather than have it gradually slow down?

Much appreciated,
davide
 
Well, you could always do it the no-budget way and just have him walk normal and then slow down (an old-fashioned human slo-mo). In post, ramp during his slow-down so he stays the same speed and the background slows instead. Test it out, you might be surprised at the result.
 
You could Rotoscope him. That way you would have the lighting exactly right.

I did something very similar in the middle of this clip.

That was all Roto. Didn't take as long as you would expect, because the backgrounds are the same. It allows you to be sloppy. If you have access to a really nice GS studio, then I would go for that, but if your GS is going to be a sheet in your garage, consider doing it this way.
 
Thanks for the input.

Josh: So in post I would speed up the footage to make it look like the main character is walking at a normal pace?

Bennis: That sounds like it could work. I've got a pretty nice green screen in the studio I use, but I worry about a) it not looking good with the Canon's 4:1:1 color samping and b) trouble with getting the lighting just right. Would you mind going over a little bit about how you acheived the effect in that clip? I've never done a rotoscope before so any advice would be really helpful.

davide
 
Josh your trick is amazing, i want to try it in some way.
Bennis your rotoed timelapse is very good, would like to see a bigger resolution.
Davide, i think for you the best solution is rotoscoping the man if the scene is not very long.
 
Set up and lock off your tripod. Film him walking in 24p. Then film the scene in 60i for slowmo.

I don't know if FCP can do roto work (never worked with it). I did mine in AE, but I know Vegas can do it to, so maybe FCP can. Anyway... Put you slowmo track underneath the normal one and use a bezier mask to "cut out" your actor frame by frame. This will allow the back slowmo layer to show through.

This could get tricky if there are people walking in slowmo between your actor and the camera. The real great thing about this is the lighting will be perfect.
 
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