Slow Motion - 3 methods?

Can somebody explain the difference in applying slow motion to a video?

I *think* there are 3 methods but not sure in which situation they apply , the pros/cons and how they work under the covers.

1) The 'speed' effect

2) Changing the speed/duration on the video contextual menu in the timeline.

3) Using the 'Rate Stretch' tool

Apologies if this documented somewhere... just couldn't find it

Comments

  • Triem23Triem23 Moderator

    Can't really go that much into how they work under the covers, but I'll tackle the situations.

    Changing the Speed/Duration of the video is best when you know that an entire piece of media needs to be at the same speed, and when you know exactly what that speed should be. Changing the Speed/Duration in the media bin will affect all instances of the media across the project. This can be helpful with, say, stock media explosions shot at a high frame rate that you might not want to be in slow motion. You can also duplicate a media clip in the media pool and assign each duplicate a different speed.

    Using the Rate Stretch tool is the most flexible and intuitive way to change speed, since you're simply dragging the media clip to it's new duration. It's great if you have a hole to fill and you don't want to do the math.

    The key with the above two methods is that they each apply a single speed to a single clip. If you're doing a "speed ramp" where you want a clip to change speeds within a single shot these can be useful if you want the speed changes to "snap." from slow-mo to regular motion, or fast-mo to regular motion. In this case I'd actually recommend duplicating the clip in the media pool and assigning wach a different speed, since this makes it easier to match up the frames where the transitions happen.

    The SPEED EFFECT is somewhat counter-intuitive and a pain in the ass. The ONLY time to use it is if you need a gradual speed change--instead of going from normal to slow in one frame, if you want the speed change to happen over a second. The way to use the Speed effect is to place the media you want the effect on in it's own composite shot, then apply the speed effect, using keyframes to build the ramp. Drag the embedded composite shot into your main comp to trim. If you're going for slow motion, you'll need to make the composite shot the new length of the clip. If you're doing fast motion, don't worry about it--just trim the embeded composite shot after building the speed ramp. Even in this case, I'd suggest duplicating the clip in the media pool and assigning one the proper speed after the ramp and only using the Speed effected clip for the actual transition--it really is a pain.

  • Excellent...many thanks.

    I might be doing something wrong but I am also having trouble with the speed effect as it isn't changing the audio. I can do that elsewhere but it's a pain. I get the point about ramping up/down though and that'll be useful.

    I've been using the speed/duration as it's..... easy. It produces pretty good results. Will play more with the rate stretch tool as well. From what I can see so far it produces a very similar output to the speed/duration but, again, can see how it's useful when filling a gap. Thanks again for the speedy reply.

  • Triem23Triem23 Moderator

    the SPEED effect doesn't change audio at all. It just alters the playback rate of the video. So, yeah, you'll have to alter the audio outside of Hitfilm.

  • Just to add one item #2 and #3 are the same function. The right click context menu option allows you to enter very specific speed values easily.

    There is one other mechanism to accomplish slow/fast motion. That is to change the framerate of an imported media item in the Hitfilm media panel context menu. If you want the same media to play at normal speed and slow/fast speed then just duplicate an imported media item and change the framerate of that one.

     

  • Rate stretch doubles or throws away frames. Speed blends them, which can produce better results. Depends on the footage and what you're doing with it. Blending works well for time lapses IMO.

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