Is there any quality difference doing slow motion in camera vs. shooting 720/60p and slowing in post?

Thanks!

I think that shooting slo-mo in camera will be quite a bit better.

This is because if you have the camera set at 24p and shoot at 60, the data is recorded at 2.5x the normal rate, so that it reconciles to 24p at 35Mbps.

When you shoot at 60p natively, the camera compresses 60 fps into 35Mbps.

Edit:
To clarify, regarding Adam's posting below, playing back material recorded at 60p at 24fps will essentially only use 35/2.5 or 14Mbps, whereas playing back material recorded at 24fps overcranked to 60 at 24fps will use 35Mbps.

This is fundamentally different from the way the HVX does it.

If you record 60fps and then use a quality slow mo plugin you can get some astounding slow mo in post

Well, although my two EX1's have not arrived, I have had three HVX200's over the last two years. From what I understand, these cameras are very similar in how they handle slow motion. So...

There is no difference in the quality between shooting 60p over 60p and 60p over 24p (slow motion). The camera is shooting exactly the same framerate in both modes. The only difference is how the camera tags and therefore plays back the footage. shooting slow motion in camera makes it a little easier in post as when you import a slow motion file it plays back in slow motion when placed on a 24p timeline. I normally shot 60 over 24 when I knew it was for slow motion. But several times I shot 60p when I needed the option of slow motion, but I also needed the sound (60p over 24p does not record sound)

Unless...
The only thing that could make shooting slow motion better quality is if the camera uses the bandwith normally used for audio and used it for video, but I doubt this. I am pretty sure the HVX does not do this, but maybe I am missiing something with the EX1.

Adam

Thanks all! Phil, can you suggest a good slow mo plugin for Final Cut?

Thanks all! Phil, can you suggest a good slow mo plugin for Final Cut?

I'm not Phil BUT I can suggest a couple I use in FCP. Re Vision's Twixtor is really good. Boris makes Optical Flow which is pretty decent as well. I use both of them.

Thanks Gabe--very helpful. Twixtor looks like the ticket. Thanks Eric also for clarifying the difference here from the HVX--one of the only places it seems like the HVX has a leg up!

Gabe does Vision's Twixtor work with HD HQ?

About the only good thing for slo-mo in post is that you can play around with the fps rate pretty easily. I've not tried 'undoing' in-camera slo-mo - has anyone else?

I really like the smooth sine wave slow motion that I do on the timeline. I can start a clip at normal speed, smoothly slow it to 15% (say) and then gently bring it back up to normal speed again. Looks wonderful in the confetti sequence.

I feel shooting slo-mo in camera is a bit like filtering the lens at the scene. Difficult to undo.

tom.

I have used twixtor for a few ex1 things in HQ mode. Also go to www.philipbloom.co.uk and look at the short "Autumns done come" for a really lovely example of everything shot 60fps (apart from the shots with cigar. I forgot to shoot 60fps and it was all done with twixtor)

Rob,

Actually I think the EX1 has the leg up here.

As long as you know what the camera is doing with your footage, you have several compression options when shooting 60 frames.

You can set the camera at 24p and overcrank to 60. The camera records something like 87Mbps onto the card. If you play back at 60 (doing a post speed up), you get a form of super high quality (though I've never tested this to see if it's worth it). If you play back at 24 you get slomo at 35Mbps.

If you set the camera to 60p, the camera records at 35Mbps. If you play back at 60, you'll have 60p at 35Mbps. If you play back at 24p (post slow down) you get slowmo at 14Mbps.

Then there are other options - setting the camera for 25p or 30 and overcranking to 60. This should give more data rate options when playing back at 60 or 24 (all would require post speed changes). I haven't tried any of these. In fact I really should test all of this more extensively before saying much more about it!

Thanks Phil it is good to know Twixtor can handle HD HQ. I really enjoyed "Autumns done come".

You can set the camera at 24p and overcrank to 60. The camera records something like 87Mbps onto the card. If you play back at 60 (doing a post speed up), you get a form of super high quality (though I've never tested this to see if it's worth it). If you play back at 24 you get slomo at 35Mbps.


Eric,
You put a very clear explanation about the compression/quality EX1 behaviors.
Unfortunately I don't get my EX1 yet, but if you make this post speed up to find out this form of super high quality, please post it. Ill be follow you.
Saludos!
Octavio

Thanks Phil it is good to know Twixtor can handle HD HQ. I really enjoyed "Autumns done come".

twixtor is great but the biggest problem with it is the long render times and the lack of preview.

Happy New year to all.

Phil What does "Autumns done come" mean?
I really enjoyed your film.

Stelios

It means the best years of your life are over

It means the best years of your life are over

Phil, Thanks for the quick reply, but if the guy in the video is you, then the best years are still to come.

Stelios

ha ha! its not me...would have been hard to film. its my dad. he is just the actor but i will forward him the comment! he will like that!

twixtor is great but the biggest problem with it is the long render times and the lack of preview.


Phil, Would you recomend the standard version of Twixtor or the Pro version....

I have been wanting this plug in for a while now...

Thanx....

Also, do you use the fields kit deinterlacer with twixtor???

ha ha! its not me...would have been hard to film. its my dad. he is just the actor but i will forward him the comment! he will like that!

Phil please tell your dad this true story:

Once they asked Zorba the Greek, why he is always vibrant and happy and enjoy life so much. He then told them this: " When I wake up is like everyday is the last and like everyday is the first day in my life at the same time".
Get your dad the book " Zorba the Greek" He will thoroughly enjoy it.

Stelios

P.S. here is another thing from Zorba
"God always forgive everything wrong we did in our lives. But He never forgives a man if a woman desires him and this man doesn't offer her the satisfaction she needs. This is the only thing according to Zorbas that God doesn't forgive to men..."

Phil, Would you recomend the standard version of Twixtor or the Pro version....

I have been wanting this plug in for a while now...

Thanx....

Also, do you use the fields kit deinterlacer with twixtor???

i dont have the pro version or know about the deinterlacer

I have never played with a camera that can do any variable speeds, so I am completely in the dark about this (and the resulting workflow in the editing room). So the only slomo (or fastmo) I have ever done has been done from the timeline (in my case FCP). I understand the principals of why slow motion done in camera (film) has a different look than slow motion done from the timeline (in camera = object appears to be "moving through a denser medium than air", as Herb Zettl puts it; in post = time slows down). What I am curious to know, is the over/under cranking features of the EX1 analogous to that of film cameras? Do you get the same frame density and seemingly absence of gravity that film overcranking gives us?

Also, what would the workflow be from shoot to post?

I played around with the slow motion in-camera and I confirm what Eric described.


Example (1) - Record at normal speed 30p (720p30)


The file size for 1 second = 5MB.

1 second realtime = 1 second in the Editor timeline/playback:


| 30 frames |
|------------------->| (Editor Timeline)
00:01





Example (2) - Record at 60 frames over 30p (slow motion in-camera)

1 second realtime becomes 2 seconds in the Editor timeline/playback:


| 30 frames | 30 frames |
|------------------->|------------------>| (Editor Timeline)
00:01 00:02



* The file size is doubled (the camera recorded twice the normal bitrate -- 35Mb/sec times two)

10 MB = 1 second realtime = 2 seconds in the editor timeline/playback.


Therefore, each second in the timeline/playback is still 5MB (35Mb/sec).



Example (3) - Record at native 60p

Drop the 1 second clip on a 30p editor timeline,
and stretch it to 2 seconds (slow down 50%) in the Editor timeline:




| 30 frames | 30 frames |
|------------------->|------------------>| (Editor timeline)
00:01 00:02



* File size = 5MB (Although native 720p60 has double the framerate of native 720p30, they're both recorded at the same 35Mb/sec bitrate.)

Because 5MB of video is streched in the timeline, there is now only half (2.5MB) of data per second (bit rate is halved).

Bernard,

Very well explained.

Mike,

Yes, it would be virtually identical. There are many samples of the 60 frame overcrank on these forums (and linked from this forum). Phil Bloom has some lovely examples on his blog.

The only thing to mind is your shutter speed. If you keep it in "angle" mode and set to 180° then you will have a very convincing film cadence.

Workflow is seamless because, when you overcrank or undercrank in camera, the camera still tags the file at a predetermined *playback* speed. Just drop it in the timeline and you are done.

So if you are in 24p mode, those clips will play back at that rate in the timeline regardless of how you over or undercranked them while shooting - and this is exactly how film behaves.

When you speed up or slow down in post (assuming you do it as a simple speed change and do not use Twixtor or Kronos or something like that) you will see a change in playback frame rate. 24 sped up to 60 in post looks fast motion but also takes on a "video" look because the screen is updating at 60 frames (or fields) per second. It gets a more present "live" look that does not cut well with other footage. Or, if you drop frames (because your timeline does not display 60fps) you get a strobier look. When you slow down in post you start to see a choppiness because you are repeating frames to fill the time.

There are many plugins that alleviate the above mentioned choppiness or strobiness (they are described earlier in this thread) that do "in betweening" and redraw th motion blur to remove the appearance of choppiness. The plugins track the movement of each pixel and synthesize frames where there are none. They work great for smaller speed changes, but start to show their limitations for larger changes. They are easily fooled by random motion (fire, water) and objects appearing and disappearing (moving behind one another). They also start to get confused by compressed footage with lower color sampling (like DV or HDV - haven't done much testing with XDCAM).

By far the best software for this is Kronos by The Foundry (who have uniquely solved many of the pitfalls associated with this process). Expensive, but amazing results.

With this software, post speed changes can approach the look of in camera speed changes. But still the best way to do it to maintain the look we all associate with "high quality" is to do it in-camera. And the EX1 does this very well.

Yes, it would be virtually identical. There are many samples of the 60 frame overcrank on these forums (and linked from this forum). Phil Bloom has some lovely examples on his blog.

The only thing to mind is your shutter speed. If you keep it in "angle" mode and set to 180° then you will have a very convincing film cadence.

Workflow is seamless because, when you overcrank or undercrank in camera, the camera still tags the file at a predetermined *playback* speed. Just drop it in the timeline and you are done.

So if you are in 24p mode, those clips will play back at that rate in the timeline regardless of how you over or undercranked them while shooting - and this is exactly how film behaves.

Many thanks for the reply Eric. I don't know anything about altering the shutter axis, but it is good to know I should be mindful of that detail.

So I guess the only bugger about the overcranking feature is that the EX1 only does 1-30fps in 1080p (while doing 1-60fps in 720p). Overcranking options whilst shooting in 720p are great, but for 1080p the limit is 30fps, which would only allow one to "reduce" the apparent speed of the action (in camera) to -- uh, I can't even begin to try to do the math on this one -- 80%, is that correct? (My math skills are embarrassingly horrible.)

I guess this posses the filmmaker with a choice between: a) shooting in a resolution that is ideal to film outs, but with limitations on in-camera slo-mo; and b) having greater in-camera slo-mo options, however shooting at a smaller resolution and having to blow your image up for film out. Is that right?

Another option for 1080 is to shoot at 60i and convert the footage to 60P
in post....

no other way to get 1080p60 with this camera...

One software plugin to help with this is Fieldskit

Another option for 1080 is to shoot at 60i and convert the footage to 60P
in post....



That's not a bad idea for those who want to stay in 1080P.

But it effectively halves your vertical resolution and adds some vertical jitter in the process. I would prefer up-resing 720p - I think in the end it will look better. Haven't tested it with this camera but I have seen the results with other HD cameras.