6 Replies Latest reply on Aug 7, 2011 4:31 PM by Peregrinecommando99

    Slow Motion Problems With Twixtor Pro in AE CS5.5

    Peregrinecommando99

      Hello forum! I recorded some footage at 1080p and at 60 fps. My shutter speed was 1/1000 and the ISO was 3200. After importing my footage and applying twixtor pro to a solid and setting the color source to my footage, i get a lot of ghosting effects. Some other things i did with Twixtor: Changed speed % to 20, Cahnged Frame Interp to Motion Weighted Blend, Changed, Input Frame Rate to 29.97, and Finally Changed Warping to Inverse w/ smart blend. Below is my video. If the emedded video below doesn't work (because I'm new to the forums), then heres the link: http://www.youtube.com/watch?v=3qGmW7or3gw

       

       

        • 1. Re: Slow Motion Problems With Twixtor Pro in AE CS5.5
          Dave LaRonde Level 6

          What is the frame rate of your AE comp?

          If your comp's frame rate was, say, 23.976, did you also conform the frame rate of the footage to 23.976 to make it 2.5 times slower to start with?

          Why did you apply Twixtor to a solid and not the footage?

           

          And if I'm reading you post correctly, you slowed down the footage by a factor of FIVE.  Twixtor's good, but it can't work miracles.  I'm not surprised you're getting a little ghosting.

          • 2. Re: Slow Motion Problems With Twixtor Pro in AE CS5.5
            Rick Gerard Adobe Community Professional & MVP

            I think your technique is correct if you have an older version of twixtor. The newer versions can be applied directly to the footage for speeding up but require you to pre-compose or apply twixtor to a solid for slowing down if the slowed clip is going to be longer than the original clip.

             

            However, I think that your camera technique was not right. Your shutter speed was too high. Slow motion with digital cameras can be tricky. The shutter speed shouldn't be any faster than 1/2 of the frame rate. IOW, if you are planning on having your video playback like it was shot at 128 fps on a film camera then your shutter speed should be about 1/250 of a second. This will give Twixtor a better chance at simulating the pixels and it will help eliminate the ghosting.

             

            Any time you make drastic increases in the number of frames you have to do a bunch of testing with Twixtor to get exactly the right settings. You may also have to do some masking and tracking. The more you ask the plug-in to do (the more you slow down the footage) the more prep work that's required. `

            • 3. Re: Slow Motion Problems With Twixtor Pro in AE CS5.5
              Mylenium Most Valuable Participant

              I agree with Dave. The slowdown is quite extreme and there will always be artifacts of some kind. It also would appear that you are still making a mess of framerates somehow - there's a definitive jerking in your footage which can only be explained by frames being skipped/ omitted. And Rick also has a point - a bit of natural motion blur due to longer shutetr phase would probably help to disguise soem imperfections and improve the result.

               

              Mylenium

              • 4. Re: Slow Motion Problems With Twixtor Pro in AE CS5.5
                Peregrinecommando99 Level 1

                I'm a bit confused... How would a 1/2 shutter speed be better than 1/1000? I thought 1/1000 was faster?

                • 5. Re: Slow Motion Problems With Twixtor Pro in AE CS5.5
                  Rick Gerard Adobe Community Professional & MVP

                  Peregrinecommando99 wrote:

                   

                  I'm a bit confused... How would a 1/2 shutter speed be better than 1/1000? I thought 1/1000 was faster?

                   

                   

                  Maybe this will help. If you were going for a target slow mo of 1/2 speed and your playback was going to be at 30 fps then you'd shoot at 60 fps. If you had a film camera with a normal shutter shooting at 60 fps wold give you and exposure of about 1/100 of a second. That means that if you have a video camera that will shoot at 60 P, or even 60I that your shutter speed should not be any faster than 1/100 of a second. Slowing down 60P or 60i footage is easy, It only gets hard when you want to slow something down to 1/4 or even 1/8 normal speed.

                   

                  Let's take 1/8 speed. IOW one second of real time takes eight seconds of playback time.

                   

                  If your project was set to 24 fps that means your target filming frame rate would be 8 X 24 or 192 fps. That means your shutter speed would be somewhere close to 1/400 of a second or half the duration of the frame rate. So I guess I should have said frame rate times 2.

                   

                  Setting the shutter to 1/1000 will give you an unnatural look to the slow mo because the edges will be too sharp. There are some occasions when you want that crystal sharp image in slow mo, but you have to be able to film the original scene at a high frame rate. Images with very sharp fast moving edges give Twixtor a very hard time. The edges end up creating weird ghosting that can’t be interpolated away. It’s just too much information for the motion vectors to successfully recreate. 1/8 speed is about my limit for Twixtor. If the camera was capable of 60i or 60p that that means doesn't mean I could slow down that original footage to 1/16 speed. It means that at 1/8 speed I'd have twice as much original information to work with and would therefore get a better result. It also means that I'd still want a shutter speed that was no faster than 1/400 of a second.

                   

                  Did you follow that? First rule of slow mo: Film at as high a frame rate as you can with your camera. Second rule: Try and emulate the shutter speed of a film camera that is over-cranked. Third rule of slow mo: Don't try and slow down too much. The amount of slowdown you can successfully achieve depends entirely on the movement in the frame. Unfortunately, the faster the motion, the harder it is to slow it down using software interpolation.

                   

                  I spent several months working with re:vision fx on deinterlacing and speed changes in interlaced footage. This advice comes from several hundred experiments on several types of footage and from 40+ years behind the viewfinder of film cameras. I hope this helps.

                  • 6. Re: Slow Motion Problems With Twixtor Pro in AE CS5.5
                    Peregrinecommando99 Level 1

                    Sorry it took me so long to get back! I've been busy. But yes that makes sense thanks!