Jerky slow down footage - C100

[Kathy Smith]

Just curious if anyone know why my footage becomes jerky when I slow it down a little in FCX. Since both the camera and the software are new to me I don't know which one is the problem. I used to slowdown 5D III footage in FC7 and it was fine. Anyone know?

[Nate Haustein]

Which framerate are you shooting with the camera? Also, is the timeline rendered? Is frame blending on?

[Josh Kallis]

FCPX has optical flow for that, but most of the time it just causes blurring and a morphing effect if subjects move too fast or overlap each other. You have to choose your shots wisely when slowing down in FCPX

There are 3 different slow down options when you look under 'retime' settings

normal
blend (iirc)
Optical Flow

[Matt Davis]

Let's say you're shooting the majority of your work at NTSC frame rates - 29.97 fps - and you're using Progressive for a 'film look'. Let's call that 30p for now.

If you want slomo, you can either shoot 1080p30 (or whatever your natural frame rate is) and use 'Optical Flow" algorythms so each frame morphs to the next with variable results, Or you use the double frame rate of interlaced video.

So, for slomo, you'd shoot at 60i - the 'traditional video look' frame rate which is devalued today, and noting that 'interlace' video gets 'deinterlaced' for display on anything that isn't a Cathode Ray Tube monitor (the big glass bubbles of yesteryear).

Deinterlacing can be done two ways: nicely or quickly. Nice deinterlacing interpolates between each scan line in a field by using standard up-rezzing algorithms, but loses 25% of the resolution so 1080p looks like 720p (that or thereabouts - actually 768 lines). Quick deinterlacing doubles up each line in a field, halving the resolution. So 1080p looks like 540p.

So, 60i to 30p slomo LOWERs the effective resolution, but looks smooth because you've natively captured the movement. Smooth but dull. This method works best on a simple 'doubling' of time (or two-times-time-and-a-halving' from 60i to 24p).

The Optical Flow process is more flexible but looks a bit processed to the discerning eye. You tend to get what you pay for, hence price of Twixtor.

Or you use the quick and dirty 'Frame Blending' default of your NLE, which is probably what you're refering to' and things look juddery. Sometimes, this is the effect you're looking for.

C100 isn't a slomo camera, but thanks to its detail, and most people's need for slomo, an Optical Flow/Twixtor solution is all you need. Beyond that, you're moving into FS700 territory.

[Chris Malley]

Have a look at settings on the camera, I've been in the same situation myself shooting on my trusty 7D.

I pinpointed it down to the shutter speed, any sense of motion blur when using an optical flow/twixtor can quite easily go to mush.

If as Mike mentioned you're shooting in "30p", at 1/60. Try doubling up next time to 1/120 or further to see give yourself a fighting chance.

[Kathy Smith]

Originally Posted by Josh Kallis

FCPX has optical flow for that, but most of the time it just causes blurring and a morphing effect if subjects move too fast or overlap each other. You have to choose your shots wisely when slowing down in FCPX

There are 3 different slow down options when you look under 'retime' settings

normal
blend (iirc)
Optical Flow

Thanks Josh. I didn't realize there were 3 slow down options in FCX. This sorted my problem. Thank you

[Kathy Smith]

Originally Posted by Nate Haustein

Which framerate are you shooting with the camera? Also, is the timeline rendered? Is frame blending on?

I solved the problem by changing to different slow down option in FCX.

[Kathy Smith]

Originally Posted by Matt Davis

Let's say you're shooting the majority of your work at NTSC frame rates - 29.97 fps - and you're using Progressive for a 'film look'. Let's call that 30p for now.

If you want slomo, you can either shoot 1080p30 (or whatever your natural frame rate is) and use 'Optical Flow" algorythms so each frame morphs to the next with variable results, Or you use the double frame rate of interlaced video.

So, for slomo, you'd shoot at 60i - the 'traditional video look' frame rate which is devalued today, and noting that 'interlace' video gets 'deinterlaced' for display on anything that isn't a Cathode Ray Tube monitor (the big glass bubbles of yesteryear).

Deinterlacing can be done two ways: nicely or quickly. Nice deinterlacing interpolates between each scan line in a field by using standard up-rezzing algorithms, but loses 25% of the resolution so 1080p looks like 720p (that or thereabouts - actually 768 lines). Quick deinterlacing doubles up each line in a field, halving the resolution. So 1080p looks like 540p.

So, 60i to 30p slomo LOWERs the effective resolution, but looks smooth because you've natively captured the movement. Smooth but dull. This method works best on a simple 'doubling' of time (or two-times-time-and-a-halving' from 60i to 24p).

The Optical Flow process is more flexible but looks a bit processed to the discerning eye. You tend to get what you pay for, hence price of Twixtor.

Or you use the quick and dirty 'Frame Blending' default of your NLE, which is probably what you're refering to' and things look juddery. Sometimes, this is the effect you're looking for.

C100 isn't a slomo camera, but thanks to its detail, and most people's need for slomo, an Optical Flow/Twixtor solution is all you need. Beyond that, you're moving into FS700 territory.

HI Matt,

Thanks for a very detailed explanation. Fortunately changing to a different "slow" mode in FCX sorted the issue. I was just looking to make already slow panning a bit slower.