slow motion

[NovelBuffalo]

Just got the mavic 3 and wondering about the difference between video and 'slow motion video' modes. It seems that the difference is just that slow motion mode allows you to shoot in 4k120fps as opposed to 4k60fps. However, I have two questions:
1. Can't I just shoot everything in 'slow motion' mode 4k120fps would that be a problem in any way even for the stuff I don't intend to slow down? I assume the higher frame rate will allow for smoother video?
2. It seems when i switch from video mode to slow motion mode the camera zooms in.. why is that? is it not just a different frame rate?

 

[CanadaDrone]

1) Yes you can. If you put 120fps footage on a 30fps timeline for example, it will just throw away the necessary frames. 120fps is maybe a bit excessive unless you are regularly using all those frames, but a lot of people shoot at 60fps all the time for this reason. Your video won't be any smoother if you are using a 30fps timeline though because you aren't adding any frames compared to just shooting 4K/30P.

The downside to doing this is that you will lose much of the motion blur effect, assuming that is desirable to you. 120fps footage would normally be shot with a shutter speed of around 1/240 where 30fps footage would be shot around 1/60, and that is going to be noticeable, especially with movement in the scene.

If you want 120fps footage to play back in slo-mo in a 30fps timeline, you divide the timeline fps by the footage fps, and slow the clip down by that amount (down to a maximum of 25% in this example).

2) I am guessing this only happens beyond either 4K/60P or beyond 4K/120P (I don't have a M3) as most image sensors are not fast enough to do a full pixel readout at the higher fps settings, so they use a smaller portion of the sensor to achieve that, and doing so effectively crops the image. At 200FPS the M3 also drops to 1080P, which is not uncommon as it further eases the processing burden of shooting at such high framerates, and they will either use subsampling or line skipping to get down to 1080P, so the 200fps quality is probably also pretty average.

 

[NovelBuffalo]

Thanks. SO I just tried it out and it looks like when I shoot in 120fps, it automatically is in slow motion - the playback plays in slow motion already. so i guess I shouldn't shoot in 120fps always anyway since the files will automatically be slowed.

 

[NovelBuffalo]

In that case, though - I suppose there is no reason to ever shoot in 4k60, right? when you can shoot in 5k50 instead. and then for slowmo stuff shoot in 4k120. Am I wrong here?

 

[CanadaDrone]

Thanks. SO I just tried it out and it looks like when I shoot in 120fps, it automatically is in slow motion - the playback plays in slow motion already. so i guess I shouldn't shoot in 120fps always anyway since the files will automatically be slowed.

This depends on your post processing timeline and how you edit it. If you are watching it straight off the drone on your phone or whatever, it's possible you will only see it as slo-mo. If you are truly getting 120fps though, you can do whatever you want with that in post.

 

[CanadaDrone]

In that case, though - I suppose there is no reason to ever shoot in 4k60, right? when you can shoot in 5k50 instead. and then for slowmo stuff shoot in 4k120. Am I wrong here?

You're not wrong, but there are reasons to use all of those, so again it just comes down to what you want to get out of it or what the intended end usage for the footage is going to be.

5K/50 requires more power to edit, and I assume that is using the full 200mbps bitrate so file sizes might be larger, however you gain the ability to do some lossless cropping/panning/zooming if your output resolution is going to be 4K anyway. You can also pull 14MP stills out of the footage which is plenty for a decent print. To my knowledge the M3 already oversamples it's 4K from a 5K frame, which is a good thing from an image quality perspective.

You can do some nice slomo with 60fps as well on a 30fps timeline (50% speed), it just won't be as slow or as buttery smooth as 120fps (25% speed), but with 60fps you can shoot with a 1/120 shutter rather than 1/240 for 120fps so it will have a different look to it. There are also plenty of displays that can actually playback 4K/60fps footage in real time.

If you want "cinematic" motion blur, you need to be shooting with a shutter speed of around 1/30 which means selecting 4K/24P or 4K/30P.

 

[jb.]

A lot of cameras that shoot 120fps then conform that to a 60/30/24 fps file internally. I know my C300 Mark III does that with it's 120fps footage.

 

[CanadaDrone]

A lot of cameras that shoot 120fps then conform that to a 60/30/24 fps file internally. I know my C300 Mark III does that with it's 120fps footage.

You can do this in post as well, the only thing to be aware of is that because you likely shot that 120ps footage at 1/240, even if you throw away frames and make it 30fps again, it will have a very different look to it than 30fps shot at 1/60.