SLow motion in composing shot

alex8276alex8276 Website User Posts: 3
edited January 22 in Post-production techniques

Hi everyone,

I apologize for my english.

I'm a beginner with hitfilm express! I have a problem when I want make a slow motion in a composing shot.

I use the speed effect. When I slow down the vidéo, I lost the end of this one.

Video 10 seconds - Composing Shot 20 seconds. If I slow the video down by 2. After 10 seconds, I saw the half of the vidéo and I have a black screen for the 10 next seconds.
Is it normal ? Else, how to make a smooth transition for a slow motion ?
Best regards


  • TheBenNorrisTheBenNorris Staff Administrator, Website User, Imerge Beta Tester, HitFilm Beta Tester Posts: 1,571 Staff
    edited January 22

    @alex8276 the slow/speed controls and effects in the software a known issue unfortunately, and it is something we are looking at improving in the future.

    If I'm correct, you are slowing down a 10 second video, resulting in only 10 seconds of footage. You may need to drag the clip to be 20 seconds long.

  • alex8276alex8276 Website User Posts: 3

     Hello @TheBenNorris

    Thanks for your answer.

    In fact, I set a composing shot to 30 seconds. I have a video that lasts 15 seconds. I set the speed effect to 0.5.

    At start The slow motion is ok , but after 15 seconds, black screen. So I can't see the end of the video in this composing shot.

    Sorry if I'm not clear.

    Best regards


  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,302 Ambassador

    @TheBenNorris so, yesterday, when I asked about files conforming to framerate, etc when added to a timeline? Here's a consequence/offshoot. Ben, scroll to the all-caps "WHY?!" below. I'm sure you know what I'll say already. 

    @alex8276 this is not a bug. T he Speed effect is working as designed, but, because of the way Hitfilm operates, the Speed effect is a pain in the butt. 

    Here's how to get the result you want using the Speed Effect: Create a 30 second Composite Shot. Name it "Video source"(use the nameof the actual clip) and add your 15 second video.

    Create a new Comp Shot. Name it "Video Slow". Drag the Video Source Composite Shot to a layer. 

    Add the Speed effect, set to 0.5 to the Video Source Comp layer. 

    A better way to do this is to duplicate the video clip in the Media Bin and rename the Duplicate (Slow). Right click on the Slow version and select "Properties." Look for "frames per second" uncheck "from file" and change the value. If it's 30, for half speed change it to 15, etc. 


    So, when you drag footage to a timeline the video is "conformed" to the timeline. A series of frames are defined in a "datablock." The Speed EFFECT applies AFTER the datablock is created. So, setting the Speed to 0.5 sets the speed of the frames in the datablock, but, once you hit the end of the block, playback ends. No more frames assigned to play. If you've used the entire clip, you can't extend the datablock because there are no frames unused. This means you get slow speed but half duration. 

    By putting the 15 second video into a 30 second comp, then embedding the comp in a second comp we've tricked the speed effect by creating a new 30 second datablock so we can slow the 15 second video.

    The Rate Stretch tool is similar but different. With Rate Stretch you are changing the bounds of the datablock dynamically, but are still confined by the conformed number of frames on the timeline. Rate-Stretching 60 fps footage on a 24 fps timeline means you're rate stretching... 24 fps conformed footage and won't get smooth slow mo. 

    So that's where we get to changing the frames per second in the Media Bin. This changes the Speed of the footage BEFORE it's added to the timeline/is conformed and is the ONLY WAY to get smooth slow motion from a high frame rate source in Hitfilm.

    Alex, this is what Ben meant by "the slow/speed controls and effects in the software a known issue unfortunately." Figure Ben might want to copy/paste my long winded explanation for future use on Speed related forum posts because we've had several this week, already. 

    TL/DR avoid Speed Effect and Rate Stretch. Duplicate clips in the Media Bin and set different frame rates there. Edit/cut between clip versions as needed. You'll get better results than Rate Stretch and less of a headache than the Speed effect. 


  • TheBenNorrisTheBenNorris Staff Administrator, Website User, Imerge Beta Tester, HitFilm Beta Tester Posts: 1,571 Staff

    @Triem23 we know that the speed effects are broken because of the conforming framerate/loss of frames, we are looking to fix it, I think all of us can agree it does not work at all like it should

  • alex8276alex8276 Website User Posts: 3

     Hello Triem23,

    Thanks, I going to try this tomorrow ! :)


  • RichB888RichB888 Website User Posts: 1

    wow! thanks Triem23, works! 

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