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elisel67131197
elisel67131197
Participant
September 15, 2018
Answered

Odd Ghosting Around Slow Motion footage

  • September 15, 2018
  • 1 reply
  • 1870 views

Hello All,

I've recently been working on a Wedding Video and for that cinematic look I've been using slow motion. I've been slowing down my clips using the speed/duration and slowing them down to 40% on Optical Flow and to reduce the shake I've nested the clips and then added warp stabilizer. I have a few clips that have been giving me a hard time. The clips include Bridesmaids walking down the isle. The original footage for these clips were shot on a Canon 70D, 24fps. These clips in particular have been giving a ghost like trail around the subject walking. It sounds strange, and I'm not sure else how to explain it.

Here is a link to the video, see part 0:42-1:15. https://www.facebook.com/eliselappanmultimedia/videos/311857762699682/

I understand it might be hard to pick out if you're not a video person, but if you look closely around the subject moving you can see this odd ghosting like effect. It's more noticeable on certain bridesmaids clips.

My question is... is this caused by the frame rate I used when filming and adding slow motion to it? Or is there another explanation to this? I hope all of this makes sense and I appreciate any feedback on this issue!

This topic has been closed for replies.
Correct answer Meg The Dog

1) If you are slowing 24fps material down to 40% of real time, then you are asking the video to play at 9.6 frames per second. These 9.6 frames, however need to be stretched out to 24 fps on a 24fps timeline. This means Premiere must repeat/replicate frames to make up the difference in frame rates, by repeating/replicating frames from the 9.6 fps to fill out the 24. Optical flow tries to smooth this out as much as possible, but it can't work miracles. Hence there is some artifact when using it. The prominence of the artifact is dependent on the amount and type of motion in the scene.

2) Usually, if your intention is to use footage as slow motion, you would shoot at a much higher frame rate - say 60fps. Then when you place it into a 24fps timeline, Premiere can take each (pristine) frame from the 60fps source and play it back at 24fps which will result in 40% speed of real time playback with out artifact.

MtD

1 reply

M
Meg The DogCorrect answer
Inspiring
September 15, 2018

1) If you are slowing 24fps material down to 40% of real time, then you are asking the video to play at 9.6 frames per second. These 9.6 frames, however need to be stretched out to 24 fps on a 24fps timeline. This means Premiere must repeat/replicate frames to make up the difference in frame rates, by repeating/replicating frames from the 9.6 fps to fill out the 24. Optical flow tries to smooth this out as much as possible, but it can't work miracles. Hence there is some artifact when using it. The prominence of the artifact is dependent on the amount and type of motion in the scene.

2) Usually, if your intention is to use footage as slow motion, you would shoot at a much higher frame rate - say 60fps. Then when you place it into a 24fps timeline, Premiere can take each (pristine) frame from the 60fps source and play it back at 24fps which will result in 40% speed of real time playback with out artifact.

MtD

elisel67131197
elisel67131197Author
Participant
September 15, 2018

Thank you so much! I had a big of a feeling that was the problem, but this answer has helped big time! For next time I'll make sure I'm filming at 60fps. Again, thank you so much! Your help is greatly appreciated.

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