# Walking around someone who is moving in Slow Motion?

In the "Buffy the Vampire Slayer" series musical episode, "Once More With Feeling", during the Giles and Buffy fight montage (Song: 'Standing in the Way') there is a scene where Buffy is hitting a punching bag in slow motion. Giles in regular speed is singing, he walks in front of her and then behind her.

I can understand how one layer is through a green screen. I'm not entirely sure how it worked for two layers in real time.

Can anyone give a quick synopses how this worked?

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## 2 Answers

Can't recall the particular shot, but the effect is commonly created using multiple composite layers

Typically there will be three layers

• the person walking in real time,
• the person in slow time,
• the background

Each is filmed separately as individual layers.

For the "people" layers only the people (and I guess the punchbag in this case) are used - the rest of the layer is transparent.

Now in editing a composite is done with the background layer, then the Buffy layer, then the Giles layer. When Giles moves behind Buffy the editor simply swaps over the order of those two layers at that point. So

• Background > Buffy > Giles

Becomes:

• Background > Giles > Buffy

The result is that they then appear behind.

Filming wise this probably means that both actors were acting in front of a chromakey (green) screen. Also if the camera was moving in the shot then a motion controlled camera is likely to ensure that each element of the composite was filmed from the same angle throughout the shot.

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I have not seen this episode, but have read that the effect is similar to the "bullet time" special effects in the Matrix. The latter was achieved using 120 still cameras in a circle surrounding the subject. The still cameras are fired sequentially (for hyper-slow motion) or all at the same time (to freeze the action instead). The single frames from each camera are arranged and displayed consecutively to produce an orbiting viewpoint of the action. Meanwhile a regular movie camera, running on a track and aligned with a laser targeting system, captures the live action.

The Matrix DVD has a special feature describing the process. Here's a link to it on YouTube:

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Where did you "read" that? links/sources? It doesn't sound the same to me at all. –  AidanO Apr 24 '12 at 8:02
Paragraph starting with "In order to understand" in Philosophical Potential in "Buffy the Vampire Slayer" -- where it discusses a slow-motion scene with Giles and Buffy in the episode "Once More, with Feeling" as similar to scenes in the Matrix. But perhaps there was more than one slow-motion scene like this. As I mentioned, I did not see the episode. –  tcrosley Apr 24 '12 at 9:04
I think that refers to the knives throwing rather than the punch-bag scene. nice link though. –  AidanO Apr 24 '12 at 11:12
Given the title of the question "Walking around someone who is in Slow Motion", I thought they might have used the same technique, i.e. a circle of still cameras as mentioned in my answer. –  tcrosley Apr 24 '12 at 12:01