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Giving the illusion of speed?

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Natalie Deans
Giving the illusion of speed?
on Dec 20, 2009 at 1:53:55 am

Hey,

I'm new to After Effects and pretty much am clueless on how to do some stuff. I'm making a short film using Premiere Pro and I need to give the illusion that parts of the shot are travelling at 2-3 times their normal speed. The main figure in the shot has to remain eventually remain stationary as the people and cars around move faster.

Any help with how to do this would be awesome.

Cheers

Natalie


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Michael Szalapski
Re: Giving the illusion of speed?
on Dec 20, 2009 at 6:34:50 pm

Do the people and cars in the shot cross behind or in front of your main talent? If so, you're in for a fun time! You'll want to read up on how to do rotoscoping in After Effects.

Basically you'll need to have your non-moving talent on one layer and your fast moving video on one (or more) other layers.

If nothing crosses your main talent, then you could do a really rough mask around them, but otherwise you're gonna be rotoscoping.

I did this once for a dream sequence in a short film. The talent was running on a pedestrian bridge in slow motion while the traffic and everything below him was flying along at very high speed. We had planned this shot ahead of time so that all we had to do was put the bottom part of the mask along the bottom of the pedestrian bridge so it looked like a seamless shot.

Planning your shot ahead is going to be key. For example, if you're going to have cars behind your talent and people walking in front of them, you might want to shoot three different passes.
One of your talent with a green screen held behind them.
One of the cars and other background movement.
One of the people who will be walking in front of your talent in front of a green screen.
That way, you won't have to do too much rotoscoping; you'll just have to do key out the green screen. (However, if you're shooting on DV or HDV you'll run into the famous color resolution issue of keying with those formats.)

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.


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Natalie Deans
Re: Giving the illusion of speed?
on Dec 20, 2009 at 7:17:59 pm

The cars and people cross the main talent briefly, the idea is to have the person walking through the crowd and to have the crowd and cars speed up gradually until the person is sitting down and stationary and everything around is moving like a blur.

My first thought was to do something like layering the clips but I didn't want to spend ages screwing around and it might not work. Since people cross the person I'm guessing I'll have to do a bit of rotoscoping and mask a bit for when they're stationary. Oh well, all in a days work.

I'll check out the tutorial. Thanks for the advice.


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Michael Szalapski
Re: Giving the illusion of speed?
on Dec 20, 2009 at 10:29:36 pm

[Natalie Deans] Oh well, all in a days work.

More like all in a week's work. (Maybe more.) So long as the camera is locked down and never moves it shouldn't be too hard to do, if you plan your shooting properly.

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.


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Stuart Elith
Re: Giving the illusion of speed?
on Dec 21, 2009 at 2:24:16 am

Michael has summed things up very well, I think.

Although it may seem like a lot of work to shoot the separate clips and layer them, i would MUCH rather do that than shoot the scene all in one and mess around with speeding it up and rotoscoping out your actor later. There are any number of comments I could include here about post work taking longer, being more painful and expensive (in time and money) than some good planning beforehand.


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Natalie Deans
Re: Giving the illusion of speed?
on Dec 21, 2009 at 11:13:01 am

I'm all for anything that doesn't take a hit on my funds, it's a college film so you can guess that my budget is pennies (being a skint student). I'd rather take the time to get each bit right than try and throw it all together at the end with something I'm not sure of.


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