6 Replies Latest reply on Aug 28, 2015 10:57 AM by Rick Gerard

    TWIXTOR slowmotion help

    Iggorr25

      Ok so if you can than please watch my 10 sec. video made in slow motion of me shooting an arrow. What am I getting so bad results. The way I made the video is this: Video recorded with a gopro hero 3 black, resolution 720p with 120 FPS, slowed down in twixtor in AE CS6.after that I used Adobe premiere to export the video out in 720 at 29 FPS so te part that is not slow mo will run normal. Can this be done any smoother?Archery slow motion shot - YouTube

        • 1. Re: TWIXTOR slowmotion help
          Dave LaRonde Level 6

          No link: can't see a thing.

          But I'd just drop the 120 fps stuff into a 29.97 AE comp; it ought to come out as a 29.97 clip in real time.  It might do that in PP too, but I'm not sure.

          For the slo-mo stuff, just conform the identical 120fps stuff -- imported a second time -- to 29.97 fps in the interpret footage settings.  It'll be just about four times slower than normal.  Want it slower still?  THEN you use Twixtor.

          • 2. Re: TWIXTOR slowmotion help
            Iggorr25 Level 1

            Ni link?.... hmmm well here it is I hope you can see this one:    Archery slow motion shot - YouTube

            • 3. Re: TWIXTOR slowmotion help
              Iggorr25 Level 1

              OK so one more thing, when I look at the properties for the footage in Windows it shows that the video is recorded at 119 FPS but it is actually 120 FPS, and when I import the video in AE I can see that the info for the footage in the project bar is at 59.94 and I can interprate it only up to 99. Why is that?

              • 4. Re: TWIXTOR slowmotion help
                Rick Gerard Adobe Community Professional & MVP

                Most folks have a misunderstanding of frame rates and playback. I've shot a lot of footage at 20,000 fps but I've never played back anything at more than 59.97 and most of my work has been at 29.97 or 24. There are lots of theories about visual perception but Douglas Trumbull, the guy that has done most of the experimenting with projection speeds says that most people cannot see the difference in any footage projected or played back at frame rates higher than 60 fps or 120fps for 3D footage with 60fps for the left eye and 60fps for the right. That's just how the human eye works. This means there is little or no reason to playback your footage at 120 frames per second and according to research the only way to get the ultimate cinema experience is to sit in a theater with a huge screen. The only practical reason to shoot at a high frame rate is to slow down time so you can see what's happening in detail. Let me explain how that works.

                 

                After Effects maximum frame rate is 99 fps. That means that the maximum frame rate that After Effects will add to the metadata of a video file is 99fps and the maximum frame rate that AE can interpret footage is 99 fps. Even though this sounds like a limitation it really does not make a difference in delivering your final product. See the first paragraph for an explanation. When your 120 fps footage was shot, if you want it to playback in real time, 1 second in real life = one second on the screen, then you'll have to play it back at 120 fps if you want to see every frame. If, on the other hand, you want your 120 fps footage to playback in slow motion, 1 second in real time = four seconds on the screen, then you open up the file interpretation dialogue in AE and interpret the footage as 30 fps (120/30 = 4).

                 

                Drop that footage in a 59.987 fps comp or in a 15 fps comp, or in a 29.97 fps comp and one second in real life will take 4 seconds on screen. Only if you drop your footage 120 fps footage interpreted as 30 fps into a 30 fps comp will you get every original frame in the rendered movie.

                 

                If you want to take that original 120 fps footage and play it  in real time for the first 2 seconds of the shot then slow it down to 1/4 speed so it is in slow motion then you open up the footage and interpret it as the same frame rate as your comp then do some math. Let's use the 30 fps example because the math is easy. You interpret the footage as 30 fps, then you drop it in a 30 fps comp. One second in real life is now 4 seconds on screen and the footage is playing in slow motion. To accomplish your speed change you enable time remapping. This puts 2 keyframes in the timeline. One at the first frame and one after the last frame. The first thing you do is move the CTI to the 8 second mark. You pick 8 seconds because you want the first two seconds of the shot to be in real time and your shot is moving at 1/4 speed. Now you add a new keyframe to time remapping. Now you move the CTI to the 2 second mark to give you something to snap to. You drag a selection around the keyframe at 8 seconds and the keyframe at the end of the shot and you then click and drag the selected keyframes so the keyframe originally at 8 seconds snaps to the CTI at two seconds. Your shot now plays back in real time for the first two seconds and then plays back at 1/4 real time or slow motion from 2 seconds to the end of the clip. If you want to gradually slow down the clip then you simply add another keyframe between the keyframe now at 2 seconds and the end of the clip. Now you grab the last 2 keyframes and drag them to the left. Open up the graph editor so you can visually see the speed changes. The steeper the line the faster the clip plays back. Here comes the trick for easing in to the speed change. The angle of the last half is the angle you want to match as the clip slows down and the angle of the first section is the angle you want to match as the clip starts to slow down. To make that easy to do you want to right click on the last keyframe and select Keyframe velocity. You want as little influence on as you can get on exit and you want to influence about half the time on entry so you set incoming to 50% and leave outgoing at .01% like this:

                Screen Shot 2015-08-28 at 3.40.55 AM.png

                Now you click and drag the incoming bezier handle to get a curve between the second and third keyframes that closely matches the angle of the first section and the third section of the timeline so I looks like this:

                Screen Shot 2015-08-28 at 3.41.43 AM.png

                This will give you real time for the first 2 seconds, then slow to quarter speed for the next two seconds, then play 1/4 speed until the end of the clip.

                 

                All of this applies to Twixtor. You just have to do the math. Set your comp's frame rate to one of the standard presets so you can playback the video on standard devices, interpret your high frame rate footage at the same frame rate as your comp and do the math so you can figure out what the speed change is. Then set things up with Time Remapping or Twixtor to get the temporal effects you want.

                 

                For your project you didn't need Twixtor at all to slow down the footage to 1/4 speed. All you needed to do was open up footage interpretation and set the frame rate of the footage to 29.97. This will show you every original frame. If you want to slow it down further then Twixtor, with some advanced settings, can do a fairly good job of creating the in-between frames as the arrow is released. You can probably slow down the footage to about 1/8 or 1/10 speed with some fairly good results but it looks to me like you only have about 5 or 6 original frames of the arrow moving across the screen. It's asking a lot for any software to turn 5 or 6 frames into 100. If you want hyper slow motion then you need to look for something that will shoot at 700fps or greater.

                 

                Pardon the crazy long post. I'm working on a book and frame rates are one of the chapters I'm trying to clean up.

                • 5. Re: TWIXTOR slowmotion help
                  Dave LaRonde Level 6

                  RICK GERARD: "Drop that footage in a 59.987 fps comp or in a 15 fps comp, or in a 29.97 fps comp and one second in real life will take 4 seconds on screen."

                   

                  For the simple reason that you're working on the frame rate chapter for a book, I gotta ask -- did you intentionally write 59.987, or should it be 59.94?

                   

                  And if you DID mean to write 59.987, why?  That's a new one on me.

                  • 6. Re: TWIXTOR slowmotion help
                    Rick Gerard Adobe Community Professional & MVP

                    Typo on the frame rate