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Thread: Motion blur on sped up video

  1. #1

    Default Motion blur on sped up video

    Hi, I have a 20 minute video that I want to speed up to 1 minute. I tried to do this in After Effects using time stretch with motion blur an frame blending on but that doesn't really do much.
    What would be the best way to accomplish this? Ideally I would like After Effects to use all or part of the dropped frames from the original as ghosts or something in the frames that stay when I speed it up. Is something like that possible?
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  2. #3

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    Not sure, I've just accepted the footage as is. I also suspect that re-interpreting the playback frame rate to 60FPS will make it look smoother as well.
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  3. #4

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    Quote Originally Posted by Grapes View Post
    Hi, I have a 20 minute video that I want to speed up to 1 minute. I tried to do this in After Effects using time stretch with motion blur an frame blending on but that doesn't really do much.
    What would be the best way to accomplish this? Ideally I would like After Effects to use all or part of the dropped frames from the original as ghosts or something in the frames that stay when I speed it up. Is something like that possible?
    Are you trying to speed up the whole clip, or only selected parts?.....

    You can get 'smooth' frame transitions using 'optical flow ' for either a speed up or slow down effects. That will need a program like Twixtor (expensive) or MVTools (free - but a bit of a learning curve!) to do that.

    If you're trying to get 'trails' of other frames, sounds like you need to use something like the 'Echo Effect' in After Effects ( see here: https://helpx.adobe.com/after-effect...e-effects.html )

  4. #5

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    I'm trying to speed up the whole clip. I tried Twixtor on a similar project over at a friend's place but while we where able to get lovely "guessed" motion blur on slowed footage we couldn't quite manage to get a nice look on a speed up. I'm sure the effect should be rather easy to make and I could do it frame by frame but with thousands of frames that will take me longer to do than I care for. Echo Effect doesn't really use the dropped frames but uses the existing ones as far as I can remember. I could be wrong though.

    Thanks for the suggestions though
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  5. #6

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    Quote Originally Posted by Grapes View Post
    . Echo Effect doesn't really use the dropped frames but uses the existing ones.......
    Trouble is, if your original frame rate was 25fps, and you're speeding up by a factor of 20, I can't see that there's going to be a lot of frames left to do anything creative with, when to comes to 'ghosting' etc.....?

  6. #7

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    Exactly.
    So what I was hoping to get was an effect that kind of like combines frames into one instead of simply dropping them on speed up. So for example if I had a range of 50 frames and I would speed that up to 10 frames, it would split apart 5 frames at a time with the first frame at 100% opacity and the 2nd, 3rd, 4th & 5th at 50% (or possibly at 50%, 40%, 30%, 20% respectively) and perhaps some additional form of blending so it only takes the difference in that frame trail.

    Perhaps that's just a really silly idea of me though and possibly the end result looks terrible... in my head it works though
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  7. #8

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    I have to say I can't see it......if - for example - you only have one and a bit frames left from every 1 second of video, time wise, you will surely only get the tiniest window (less than 40mS ) to display any additional ghost frames before the primary frame from the next second of video needs to be displayed?
    Not sure how you 'mix' the primary information and the 'ghosts' of each displayed frame......there's not enough time, surely?......Unless I'm missing the point altogether.....

  8. #9

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    I believe this illustration illustrates my train of thought:

    If a dot would move in 6 frames from left to right with a slight curve and I'd speed that up to two frames and add Echo Effect I think it would guess the direction and interpolates ghost images? That would mean they go in a straight line?
    Attached Images Attached Images
    Last edited by Grapes; 03-24-2017 at 11:50 PM.
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