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Any TIPS for Slow-Motion @ 60fps??

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Jim Lino
Any TIPS for Slow-Motion @ 60fps??
on Jul 13, 2018 at 3:43:32 pm

Hi there!

Using a Canon Rebel 70D @ 60fps and 1080p
i7700 cpu & GTX 1070 gpu with 16gb ram


So I'm shooting car-related video..... just like sexy car shots.

However, when I slow my clips down in Premiere (typically to like 80%), I'll notice a jitter or jump or frame tear (same thing, not sure what you wanna call it) every now and then.

And especially if I speed the clip down... then nest it.... apply Warp Stabilization.... I'll almost always get this frame jittering.

What's worse.... is that sometimes I'll concede to the frame jitter..... go in, remove that single frame..... make sure the clip looks smooth again..... and then a few minutes later, there will be a NEW JITTER somewhere else on that same clip. wtf?!!

I used to think it was the limitations of the previewer... like, of course, it's not a full render so there will be hiccups.... however, once I export the final video..... those hiccups always remain in the final video..... almost meaning the damn previewer does its job pretty well and shows me a true 1:1 representation of the final look.


Under sequence settings, I've tried different Editing Modes, etc. Currently, I've settled on using DSLR with a 60fps Timebase.

Perhaps I'm holding myself back some way?? Any help here would be much appreciated.

Thank you!!


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Blaise Douros
Re: Any TIPS for Slow-Motion @ 60fps??
on Jul 13, 2018 at 5:22:16 pm

When you shoot for slow motion, you need to use a faster framerate than your main timebase.

If you want to be able to really slow down your shots, you need to use a 23.976 timebase, and Interpret Footage so that your 59.94 footage is showed at 23.976, which is slowed down by 2.5x. Or use a 29.97 timebase, which is a 2x slowdown. Right now, with a 59.94 timebase, slowing down your footage just stretches existing frames across others, which creates the "jitter" you're describing.

This is pretty basic stuff, so you may want to find some tutorials on shooting higher speed framerates for a slower timebase so that you can really understand it before going out and making mistakes on set.


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Jim Lino
Re: Any TIPS for Slow-Motion @ 60fps??
on Jul 13, 2018 at 8:56:54 pm

Well, I've been experimenting with all different settings to try to figure it out. The 60fps timebase was just my current setup this time.

Creating a new project, changing to a 25 or 30fps timebase did not solve this issue. I got just as many frame tears as before. ☹

Thanks for the reply, Blaise.

Could this be a hardware issue? Needing more than 16gb ram??


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Blaise Douros
Re: Any TIPS for Slow-Motion @ 60fps??
on Jul 13, 2018 at 9:54:24 pm

You need to interpret the footage to fit the project timebase. Highlight the footage in the bin, right click it, and select Modify > Interpret Footage. Set the framerate to your project timebase. Now the footage will play back, frame for frame, at the same framerate as the sequence, without changing the Speed setting.

If your machine has issues playing back 60p footage, you might see some horizontal tearing during playback, but you wouldn't see frame jumps unless there's a framerate mismatch between your project and your media.


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Jim Lino
Re: Any TIPS for Slow-Motion @ 60fps??
on Jul 16, 2018 at 7:31:01 pm

Right, that's what I shoot at.... 1/125th @ 60fps.

Now, here's one of the reasons for my confusion....

When starting a new project and before even importing the raw footage, if the sequence settings are set to 29fps or 25 or whatever (the default for DSLR Editing Mode)..... as soon as I go to make my first edit on the timeline... a message will pop with Premiere suggesting I change the sequence settings to match the footage.

I can choose "no, keep current settings".... but in the past, I've typically chosen to go with its suggestion and match the footage. And if that footage is 60fps... the timebase becomes 60fps. So where am I going wrong there?

But ok, interpret footage, I'll make use of that now. Workflow-wise, you use "interpret footage" really on a clip by clip basis, then, correct? You're using interpret footage primarily for slow-motion purposes and just modifying that clip when the time comes?

Thx again!!


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Blaise Douros
Re: Any TIPS for Slow-Motion @ 60fps??
on Jul 16, 2018 at 7:59:52 pm

If you need to work at the native timebase of the 60p footage, you can still interpret the footage to an even-numbered division of that framerate to get 50% speed slow motion. So you work in a 59.94 timeline, interpret the footage as-needed to 29.97 for 50% speed. That way, you get an even distribution of frames across your timeline, so no tearing--it just doubles up the frames displayed.


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Ryan Neuman
Re: Any TIPS for Slow-Motion @ 60fps??
on Jul 16, 2018 at 5:12:29 pm

The proper work flow for this would be: 24fps timeline, shoot 60fps, 1/125th shutter speed, and slow the footage down to 40%, I usually get pretty smooth results following this formula


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Jeff Pulera
Re: Any TIPS for Slow-Motion @ 60fps??
on Jul 16, 2018 at 8:21:19 pm

If you shoot 60fps, and edit in a 60fps sequence, all frames are being "used" already. Therefore, any slowing down of the footage means some frames MUST be duplicated. So if you set clip speed to 50%, each frame will be shown twice. That does not explain tearing, but will get to that later.

So create a 29.97 sequence (30p) and drop that 59.97fps (60p) footage into it. Disregard the request to change frame rate of sequence. And NO NEED to Interpret frame rate - unless you automatically want every single clip to play in slow motion, then you can do that.

When a 60p clip is played in 30p timeline, that timeline is only going to display 30 frames each second, but your clip has 60 per second, right? So what Premiere will do is simply skip every other frame, only playing half the frames, basically treating clip as if it is 30fps. Looks fine. Premiere assumes you want to see normal speed playback so it does this adjustment automatically, allowing you to mix clips of different frame rates together and have them all play normal speed.

Then if you set 50% speed on that clip, that would make a 5-second clip 10 seconds long. You have 300 frames to play with (5x60fps) and 10x30fps = 300, meaning every frame is played once, so you get perfectly smooth slow motion with a new frame played every time, no duplicates. If applying 40% speed to 60fps clip in 24fps timeline sequence, same thing, every frame used once, like the others stated. So then you also export at same frame rate as sequence, either the 29.97 or 23.976 for instance. Clips that do NOT have speed change applied play at "normal" speed, but if you apply the slow speed to select clips, you get that silky slow motion. Good so far?

Now about the tearing - the Warp Stabilizer is a finicky beast. Probably not going to play well with slow motion for various reasons, especially if using 60p clips in 60p timeline, slowing them down (frames duplicated) then also stabilizing, lots going on there!

What I would do if you need to stabilize a clip is this - put 60p clip in 60p timeline, and stabilize. Now EXPORT that clip as 60p using a good intermediate (lossless) codec like DNxHD (.mxf) or GoPro Cineform (.mov). Then, take that new already stabilized 60p clip and put it in the 30p (or 24p) sequence and add your slow motion or 50% or 40% as applicable. Can pretty much guarantee that will bypass the tearing issues you are seeing.

Hope this makes more sense as explained

Thanks

Jeff Pulera
Safe Harbor Computers


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Blaise Douros
Re: Any TIPS for Slow-Motion @ 60fps??
on Jul 16, 2018 at 9:01:03 pm

Good post, Jeff.

One thing to add--if you use the method of Interpreting footage, Warp Stabilizer will play nicely with it. However, if you've changed the speed of the clip either using timeline keyframes or the Speed/Duration dialog box, Warp Stabilizer will NOT work.


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Jim Lino
Re: Any TIPS for Slow-Motion @ 60fps??
on Jul 16, 2018 at 9:28:48 pm

Ok thanks a lot. Those tips reaffirm things.

However, I think this is a hardware issue now. I'm having these problems at the work pc.... I took my project home and am not getting the frame tearing, after I redo the sequences.

I had really always just been doing it a basic way -- 60fps and applying speed effects or regular time remapping.

After reading your advice, Modifying>Interpreting the clips individually that I wanted to slow down did make a smoother difference instantly.... and it did look nicer with the Warp Stabby. I'll also try that longer method of exporting the stabilized clips, too.

Now, my IT guy is trying to figure out what could be wrong with the work computer.

It's almost identical to my home pc.... they're both intel core i7700k, 16 ddr4 ram and a nice gtx 1070.

On occasion, the work pc has shown a GREEN SCREEN in the top-left source viewer window...... it's shown single RED FRAMES when scrubbing thru raw footage..... and some other weird issues.

Thanks for helping me with my workflow situation.... don't really wanna bother you guys with these troubles. I'm sure he'll figure it out.... maybe the previous video guy before me was mining some bitcoin on the side with the gpu or something and wore it out...?


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