slow motion?

[PhilPowers]

Hi guys - I have been asked to shot a sequence where a scientist will break a wine glass with powerful sound waves. I have seen this done before and can remeber it fracturing very fast. My director has asked if this action can be slowed in any way. Can you advise me? It will be shot on digi beta and we will be able to do the demo a number of times. I also have a PD150 "ehh!" at my disposal. There has been mention of some split screen stuff.

 

How can I make this look good using video??

 

Any sugestions would be gratfully accepted..

 

All the best - Positive Phil. B)

[Alvin Pingol]

Several ways to go about slow-motion on video, some being far better than others.

 

The first thing to remember is shoot with a shutter speed of 180 degrees or smaller (1/120th or faster) [note: I am speaking in terms of NTSC]. Using open shutter, 1/60th, will create ugly blurring when the footage is slowed.

 

In post production, run the 60i footage through a process called Bob deinterlacing. This takes your footage and converts fields to frames while shifting them half a pixel up or down (depending on whether it is even or odd), thus creating a 60fps stream. You now have a lot more information to work with. There are several ways to Bob deinterlace. I find a combination of commands in AVISynth work well, but it may be a bit much for you if you haven't used AVISynth before. A VirtualDub filter will work fine, as well.

 

From the created 60fps stream, the only way to get more information is through interpolation. One method is frame blending, as such:

 

1

1+2

2

2+3

3

3+4

4

4+5

5

5+6

 

and so forth. Doing this will result in a 120fps stream. I achieve this in, again, AVISynth. I am not sure if there is a VirtualDub filter that will do this.

 

The next way is through motion estimation interpolation. An application like Dynapel's MotionPerfect as an example. This method takes the longest but can provide the best results. The software looks at frames 1 and 2, applies motion vectors, then decides what should go inbetween and creates a frame. It does this in between every frame (or thrice between every frame if you tell it to). I usually get mixed results, but the quality largely depends on the video subject matter. This is where shooting with fast shutters really comes into play, as it is difficult for the motion estimator to place vectors on images with motion blur.

 

Now, you can combine these two methods to get some super slo-motion, but it won't be perfect. If you decide to, just be sure to do the motion estimation interpolation BEFORE the frame blending.

 

Essentially,

 

60i --> 60P --> 120P --> 240P, so thats 240fps you can slow down to 24fps, 1/10th of the original.

 

Or,

 

60i --> 60P --> 240P --> 480P, so that's 480fps you can slow down to 24fps, 1/20th of the original.

 

The steps are

RAW --> Bob --> MotionPerfect --> Frame blend.

 

I chose 24fps as the final output because it is the lowest framerate before everything starts looking too "choppy."

 

Hope this helps.