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Slow Motion Stutter


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#1 Sacha Sojic

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Posted 13 October 2007 - 07:41 PM

I'm seeking assistance from the members of this forum with the following issue:

We're shooting a commercial this upcoming week that opens with a young lady gracefully popping up into the frame in glorious slow motion. This will be simply acheived by having our actor jump up and down on a trampoline while we wait for her, framed at the top of her trajectory. To get an idea of what I'm talking about, I posted a clip of the test footage we shot last week at the following location.

Trying to avoid the film route, I shot these tests with the HVX-200, overcranking it to its maximum of 60fps and interpreting them at 23.976. The concept requires the compositing of the shots onto colorful backgrounds, so we're shooting everything on green. I'l be using a high speed shutter because the concept calls for it but also because the sharp images will help the key quite a bit.

The client has viewed the tests and finds that the footage seems too stuttery. I attribute this to the fact that the shot is fairly tight, and that the subject enters the bottom of the frame at high velocity. The frame rate being insufficient to sample enough moments in time, the subject has traveled to far between samples and the eye perceives a jump. This effect is, of course, accentuated by the absence of motion blur in the shot.

My question is the following: Given the fact that a narrow shutter is required by the concept (and very helpful in post), is my only option to shoot at a higher frame rate to eliminate the stutter? If so, is film the only option? That said, I'm desperately trying to avoid the Phantom Cam. Although I've heard some good things about it, Ithe workflow associated with it is just too heavy. We have many other shots to can aside from the aforementionned one and I'm trying to keep it as lean as possible.

Best,

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Sacha Sojic
Montréal, Québec
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#2 Michael Collier

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Posted 13 October 2007 - 08:26 PM

THis might be a small overlook of settings during the 23.98 pulldown. I am sure you looked at this, but make sure your feilds are in the right order. if the feilds are reversed then you will find the image has a lot of stutter to it. If that doesnt work then I would venture to say it is the shutter that makes it look the way it does. hopefuly that will solve the problems. 60p played as 24 should look smooth
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#3 monday sunnlinn

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Posted 13 October 2007 - 08:52 PM

the newest incarnation of the final cut pro suite has a really good slow-mo in Motion3. i took a busy street scene in south beach(miami area) with lot's of palm fronds and people moving in various directions and speeds and slowed it down to about 33 percent before the algorithim started to become ineffective. it's in the app called motion using the "optical flow" setting, the work flow is fairly easy. since it creates intermediate pixels, it adds a little bit of blur to it. another thing you could do is add motion blur after you key it. it might give you a cool look. after effects has a third party plug-in called reelfx-motion blur from revisionfx.com.

or come to think of it, you can hire me to do it.... ;)

Edited by monday sunnlinn, 13 October 2007 - 08:53 PM.

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#4 Michael Nash

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Posted 14 October 2007 - 01:04 AM

I'l be using a high speed shutter because the concept calls for it but also because the sharp images will help the key quite a bit.

The client has viewed the tests and finds that the footage seems too stuttery.


The fast shutter is what causes it. There's nothing wrong with the pulldown or the framing; that's just what motion sampled with a fast shutter looks like.

You say the "concept requires" the narrow shutter, yet the client objects to the stuttery look. Does that mean the client hates the concept? You can't have both!

You can try a shutterspeed that's not quite as fast if you feel that "normal" motion blur will cause you problems in keying. But motion blur is what makes motion look smooth; lack of motion blur is what makes it look stuttery. You can't have both no motion blur and smooth playback.

You can try adding motion blur in post as suggested, but then that would be un-doing the "look" created by shooting with a fast shutter. Or, shoot at a faster frame rate so that motion blurs less per frame, and plays back slower as well.
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#5 Elhanan Matos

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Posted 19 October 2007 - 02:21 PM

I worked on a small promo for G4TV where we had some actors jumping on trampolines and we were fairly tight on the lens, we had the same problem. We found the best speed is about 500fps with a 360 degree shutter.
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#6 David Mullen ASC

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Posted 19 October 2007 - 02:53 PM

As Ethan could tell you, there are digital alternatives to film for super high frame rates, cameras like the Phantom HD and the CineSpeed.
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#7 Sacha Sojic

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Posted 22 October 2007 - 10:38 PM

Thank you all for your respective input.

We ended up shooting 720P at 60 fps with the shutter at 1/1000th on the HDX-900 and everything turned out okay. I chose to frame the shots a little wider and that helped diminish the perceived stutter a bit. Strangely enough, I think the solution came through the use of a sharper lens, in this case a Canon CineStyle zoom. From a purely subjective standpoint, I found the images to be so sharp that they married well with the choppy motion. In comparison, the HVX's onboard lens produced much softer images during tests. So despite their choppy nature they just felt a little wrong.

As far as shooting with the Phantom camera is concerned, I've been trying to avoid it! Perhaps I'm beeing too cautious but I hear it's not for the faint of heart. A local production company here in Montreal recently rented our studio space to shoot a commercial with the Phantom HD. They spent nearly eighteen hours on set, mostly dealing with technical issues related to the camera and its complex workflow. If anyone has had a pleasant experience with the little devil, do share - unless the discussion belongs in another thread!

I've never used the CineSpeed sysytem although I know it's been around for a while longer than the Phantom has. Perhaps I'll look into it for the next slomo show...

Thanks again

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Sacha Sojic
Montréal, Québec
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#8 Michael Nash

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Posted 23 October 2007 - 02:46 AM

As far as shooting with the Phantom camera is concerned, I've been trying to avoid it! Perhaps I'm beeing too cautious but I hear it's not for the faint of heart. A local production company here in Montreal recently rented our studio space to shoot a commercial with the Phantom HD. They spent nearly eighteen hours on set, mostly dealing with technical issues related to the camera and its complex workflow. If anyone has had a pleasant experience with the little devil, do share - unless the discussion belongs in another thread!


Mitch Gross, Kevin Zanit or Elhanan Matos would be the guys here you want to talk to.

Glad it turned out well. I think the HDX900 camera had as much to do with the increase in sharpness as did the lens (compared to the HVX).
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