OVERCRANK: why not always 60fps

Steve Kahn

Steve Kahn

Well-known member
I'm shooting a dream sequence tomorrow and while I've done tests with 60 and 48 fps a question comes to mind...

If you're going for a slow motion effect why not always shoot at 60fps and then time warp in post to taste?

Understood you lose a small bit of light but the flexibility you gain is immense. Also not having to shoot multiple takes at multiple frame rates is a bonus as well - in the event you haven't locked down the perfect frame-rate for the scene.
 
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Call me old-fashioned, but I'd rather to do it in camera. I like to work with real frames (or at least the "real" frames the codec delivers!).

Though I suppose it could be more of a preference thing now.
 
If your shooting 60p, you are working with real video frames unless you slow it down past the standard 24 fps (assuming this is your time base) The NLE would just toss out unnecessary frames. Maybe I'm thinking of this in a backwards way but I think Steve has a point here. If you have the space on the card, I see no reason not to.
 
Can you do it? Absolutely. And it can certainly open up some options in post.

Would you really be tossing out frames? If you did that there would be gaps in the action. I assume (and I'm no post guy, so correct me if I'm wrong) that you are blending those 12 frames in there somewhere. I guess there are ways to make that look good, as I've seen some decent digital ramping done before. But I just like a frame to be a frame.

If you shoot at 60 fps with a 180º shutter and blend frames in post to make it 36 or 48 frames, I would think the motion blur would look a little off.

In the end it's probably not that big of a deal. I just think in terms of the camera's capability, whereas Steve sounds more like a post guy. I would love to see some samples of this idea in action.
 
I will say this, almost ALL slow motion content I have seen recently on television or in movies is CLEARLY 24p slowed down. It's jumpy and not smooth at all. Has anyone else noticed this? I love the look of 60fps slowed down to 24 but I also thought to myself, the stepped motion of slowed down 24p had a look to it and I did like it as well. Something to ponder.

To me, with the 60fps I get the most freedom because if I need slow and smooth, this is the best to get it. While the motion blur might be off somewhat at slower rates, it still feels unnatural anyways since nothing moves that slow! :)
 
Taylor Rudd said:
If you shoot at 60 fps with a 180º shutter and blend frames in post to make it 36 or 48 frames, I would think the motion blur would look a little off.
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I think you are right. If you're shooting 60p at 180degrees then transformed to 48p in post that becomes the equivalent of 144degrees or 90degrees at 30p. So less motion blur it would seem but not that much less at 48 vs. 60. And, I don't think it would be that hard to dial in more motion blur with AE in post.

I agree though, Taylor, it is best to get it in the camera. I bring up the idea only if you don't know and/or want the flexibility to change your mind later.
 
I don't have an AF100, so I haven't tried this. However, I will point out a couple things that will apply no matter which camera you are using.

1) If you are aiming for a traditional cinematic look, following the 180 degree shutter rule is typically the way to go. Basically your shutter speed should be twice your frame rate.
2) If your shutter speed is set to twice your frame rate at 60 fps (1/120 or so) and you are typically going to just use it at 24 fps, you will have lost over one full stop of light. ISO 800 becomes ISO 1600, f/2.8 becomes f/4 (but with f/2.8 DOF), etc.
3) If you want to maintain the 180 degree shutter rule throughout your footage, you would want to shoot 24 fps content at 1/48 (or 1/50), and shoot 60 fps content at 1/120 (or 1/125).

Of course, feel free to disregard any of this. My gut reaction though would be to shoot at the frame rate you intend on using in post and try to avoid conversions if you can avoid it.
 
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And I will say, the CC Force Motion Blur in After Effects takes FOREVER to render :) It's really cool and used for footage that you want to add in from the content you see, but wow, I was amazed at how slow it renders.

Also, if you do use it, increase the frames to sample to 16, not 8. It makes a big difference. And also remember, you have to use it on an adjustment layer OR on a precomposed layer as the only item on that layer.
 
Would you really be tossing out frames? If you did that there would be gaps in the action. I assume (and I'm no post guy, so correct me if I'm wrong) that you are blending those 12 frames in there somewhere. I guess there are ways to make that look good, as I've seen some decent digital ramping done before. But I just like a frame to be a frame.
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It depends on what post-production programs you are using, but time remapping usually involves frame interpolation. Some ways look better than others.

Folks make an interesting point about the frame angle, if the goal is to make the effect accurately look like overcrank with a 180 degree shutter. I kind of like the look of dramatically changing speeds within a single clip.
 
Rick Burnett said:
And I will say, the CC Force Motion Blur in After Effects takes FOREVER to render :) It's really cool and used for footage that you want to add in from the content you see, but wow, I was amazed at how slow it renders.
Click to expand...

What version of AE?

With CS3, that I am using now I can't tell you how many times I've crashed my 8 core workstation because I didn't pre-compose footage.
 
It can be a great effect. I have been trying to brainstorm a way to go from normal 24p to dramatically slowed down footage. My thought is to use 60p and then slow the footage down even further using time-remapping. I still haven't thought of a good way to go from 24p to 60p for the original footage though. So far, I can only think of doing it all at 60p and speeding the footage up to 24p.

If you all think that the render time in CC Force Motion Blur is bad, try working in some of the 3D programs!

Edit: Has anyone else seen Zombieland? That movie is very silly, but they did a lot of really fun time-remapping and titling in the film.
 
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Yes, for sure on the motion blur. I have been stuck brainstorming on going from 24p to the effect for some time. This is just for fun. I plan to do something similar for a more serious project, but it will all be CG.
 
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Three things come with it:

1. Light loss.
2. Less motion blur (and therefore slightly differently rendered motion).
3. Pullup or frame interpolation (when you shoot at 60p and conform to 24p).
 
Heh, well I am very experienced with Maya and Blender. I know EXACTLY of what you speak :) The worst part is getting it right and getting the different materials to work properly in the motion blur. Now at to that using Blastcode for destruciton stuff and it gets even worse :)
 
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