I’ve always been fascinated with slow motion film and video. It adds another dimension to a visual piece of work by allowing us to see something our eyes cannot capture in the everyday physical world.
The employment of slow motion video is used everywhere in mainstream popular media. Music videos, for example, are perhaps the most popular medium for slow motion video along with professional sporting events.
The advances in technology over recent years has brought slow motion capture to prosumers and video enthusiasts. It’s affordable to purchase cameras that can capture up to 1200 frames per second (fps). Just type that into youtube and see how many hits you get. It’s fun seeing what looks good in ultra slow motion! However, such speeds come with compromises, the main one being resolution. The capability of modern prosumer cameras that can shoot high speed can only do so at considerable ‘cost’ to resolution size. But there are ways around this obstacle by using certain software on the market today.
The video of the ice-cube hitting a table above, I captured at 300fps. However what you see is not 300fps, it’s double that. Not only that, but the resolution of the video is twice that of what the prosumer camera I used was capable of achieving. This post aims to show you how to take your slow motion footage further by using additional software to improve your videos.
This is the high definition camera I use for my slow motion work. I think if I was looking at it now, I may be more inclined to pay a little more and go for the Canon 7D which is capable of 60 frames per second at 1280 x 720 (720p) and then to slow the resulting footage down further in post using Twixtor. Compare the 7D to the EX-F1 which is capable of 60 fields per second at 1920 x 1080 (1080i).
“What’s the difference?” I hear you ask. Well, I thought at the time that the Casio must have the better resolution. But 1080i is really a marketing gimmick. What I didn’t understand at the time, which I do now, is that motion is different issue. If you want to see motion clearly, then live action 720p is what looks best, compared to 1080i. Here’s why: The information content of 720p is about the same as 1080i, though what it lacks in spatial resolution, it makes up for in temporal resolution (because the picture is at 1/60th of a second, not 1/30th x 2.) On 1080i, this would show as flickered or jagged edges on bright horizontal objects (like in the background of a camera pan).
However, I am still happy with the F1. If only I could interchange the lens I would be far happier. Anyhow, this is what I have and here are the specs we are concerned with:
Casio EX-F1 Image Capture Specs
- 2816 x 2112 is max output resolution (photos)
- 1920 x 1080 at 60 fps (1080i)
- 512 x 384 at 300 fps
- 432 x 192 at 600 fps
- 336 x 96 at 1200 fps
As you can see, the faster the frame rate, the lower the resolution becomes. Also it should be noted that at speeds of 1200 fps, you need to throw a lot of light at the subject. When I say a lot of light, I mean a LOT. This is the same for any high speed camera, even the £60,000 professional high speed cameras. It’s obvious if you consider how fast the shutter has to operate to capture this footage.
We use the time remapping technique to extend the duration of the slow motion footage further. We do this even if faster fps rates on the camera are available. The reason we do it is because a higher resolution is available at the lower fps rates on the camera. The following video of waves washing up on rocks has an original resolution of 512 x 384 because it was shot at 300 fps on the Casio EX-F1. However it’s been further slowed in post production using software known as Twixtor to achieve the look of 600 fps. Had I used the available 600 fps rate on the camera, my resolution would have been a mere 432 x 192 – Arguably unusable footage other than as a novelty.
The exact process involved to make this to happen in Twixtor is outside the scope of this post and I intend to cover this in a tutorial for people if it is asked of me. There used to be a good tutorial available online in the form of a step-by-step guide, but it’s gone now. There are a couple on this page. There is other software that will, in theory, do the same thing. For example, Shake, or even Adobe After Affects ‘Time Remapping‘ effect. But of all of them, I found Twixtor the best for advanced frame blending through intelligent algorithmic creation of new frames.
Whatever software you use, the general principle is the same. Take footage at higher resolution of 600 frames per second, then slow it down further by using time remapping software. I’ve discovered through experience that as much as 50% slower is acceptable without the footage looking drab… But then it does depend on what footage you have initially.
The second method I use to enchance the slow motion video I create with the Casio is resolution resizing. Of course its possible to just try to scale it up yourself in your favourite video editing software. But if you really want it to look good, you can use software like Red Giant’s Instant HD.
I captured the footage at 512 x 384 (300 fps) to maximise the resolution. I then slowed the footage further with Twixtor in AE. Finally, the footage is scaled by Red Giant Instant HD 1.1. For the diffusion look I used another 3rd party plug-ins called Neat Video. This is normally used as a noise reducer, but I have used it here to create a softer look effect.
Using Instant HD is a great way of scaling from standard to high definition (HD). The software uses algorithms to generate the missing pixels and also employs integrated sharpening and anti-aliasing techniques.
I look forward to passing on more tips and tricks in future posts!