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Compositing, Undercranking, Motion Blur, and more...


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#1 Dustin Pearlman

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Posted 27 June 2007 - 11:14 PM

I'm looking for any advice/guidance for a VFX plate that I'm shooting on Friday.

We are shooting a steadicam shot through a forest and the idea is to recreate the effect as seen in the chase in Jedi. This plate will be composited with a woman running on a treadmill. The idea is that she is running very quickly through the woods...

We are mainly concerned with motion blur as a result of our going down to 6fps. Any tips/experience in this realm would be excellent!

thanks,
Dustin
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#2 David Mullen ASC

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Posted 27 June 2007 - 11:43 PM

I'm looking for any advice/guidance for a VFX plate that I'm shooting on Friday.

We are shooting a steadicam shot through a forest and the idea is to recreate the effect as seen in the chase in Jedi. This plate will be composited with a woman running on a treadmill. The idea is that she is running very quickly through the woods...

We are mainly concerned with motion blur as a result of our going down to 6fps. Any tips/experience in this realm would be excellent!

thanks,
Dustin


The blur should be "correct" if you shoot at 6 fps with a 180 degree shutter (1/12th of a second per frame). That's how they shot it for "Return of the Jedi". You need that blur for it to look fast, as opposed to sped-up.
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#3 Nick Mulder

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Posted 28 June 2007 - 12:24 AM

I think most of the shots where you see the speeders and track with them were shot in a forest that was a scale version of the one you see in the other shots... Not a scale model, a similar look but smaller tree's plants etc...

I'm not %100 on the validity of this but I heard when I was back in school (a very young'n!) that the local bush here in NZ was used by the Jedi second unit for this... I've spent many a day in there riding bikes n wotnot, and yes it does look like a scale endor
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#4 Dustin Pearlman

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Posted 28 June 2007 - 01:14 AM

The blur should be "correct" if you shoot at 6 fps with a 180 degree shutter (1/12th of a second per frame). That's how they shot it for "Return of the Jedi". You need that blur for it to look fast, as opposed to sped-up.


David, I understand that the blur would be "correct" with a 180 shutter, however, the post guys are concerned that they want as clean of an image as possible for keying/tracking purposes. I will definitely do a pass at 180 as per your recommendation. We are also using an Arri-III, which makes me a little nervous about it's registration. However, the thought is that the under cranking would make the registration less important than say over cranking. Any thoughts?

Thanks for your speedy response!

Nick, thanks for your response as well. We aren't looking to copy the Jedi shot, it is just a visual reference...miniatures would be great. Then we could use the money for steadicam on a Frasier...
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#5 David Mullen ASC

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Posted 28 June 2007 - 01:38 AM

David, I understand that the blur would be "correct" with a 180 shutter, however, the post guys are concerned that they want as clean of an image as possible for keying/tracking purposes.


Doesn't make sense -- it's the background plate, so you're only keying something in front of it. Besides, if you shot at 6 fps with a 45 degree shutter, so the exposure time was 1/48 instead of 1/12... the shot would look identical if you simply took 24 fps footage and sped it up. And then they'd have to fake the correct blur.

Sure, tracking will be a pain but that's just the nature of the shot.

Garret Brown had a green string run through the woods that he used as a guide, plus levels with bubbles to maintain his horizon.

The side angles where shot normal speed from a moving vehicle on a road parallel to the woods.

They didn't really use miniature woods for that sequence.
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#6 John Sprung

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Posted 28 June 2007 - 12:53 PM

David is absolutely right. The background plate can be anything. It's the photographed boundary between the foreground person and the blue or green screen that creates the matte.

That being said, though, you still need adequate motion blur on your foreground action to have the illusion of motion, rather than an excessively rapid slide show.

Lighting, depth of field, color, and motion blur can each give away the trick if they don't match well enough between the BG and the action. This is absolutely doable with a 180 degree shutter. Ask to take a look at some previous work your effects vendor has done.



-- J.S.
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#7 Dustin Pearlman

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Posted 29 June 2007 - 02:28 AM

Doesn't make sense -- it's the background plate, so you're only keying something in front of it. Besides, if you shot at 6 fps with a 45 degree shutter, so the exposure time was 1/48 instead of 1/12... the shot would look identical if you simply took 24 fps footage and sped it up. And then they'd have to fake the correct blur.

Sure, tracking will be a pain but that's just the nature of the shot.

Garret Brown had a green string run through the woods that he used as a guide, plus levels with bubbles to maintain his horizon.

The side angles where shot normal speed from a moving vehicle on a road parallel to the woods.

They didn't really use miniature woods for that sequence.


Thanks again for the guidance. I kind of got thrown to the wolves on this one.
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Visual Products

Wooden Camera

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