How to create slow motion video with Lumix cameras

We see a lot of slow motion video on TV, in the cinema and in online films because showing the world slowed-down not only helps to reveal the details of how high-speed events take place, but it can also support the creation of atmosphere while injecting a little more drama into every day occurrences. In wildlife documentaries slow motion footage allows us to see every detail as the lizard’s tongue lashes out for the fly, but in real-time it all happens in such a flash we’re as oblivious as the fly about what’s happening. And, with a romantic backing track, the waves breaking gently on the shore as the happy couple stroll along the sunset beach transport us, and them, to another dimension.
Slow motion video is, in its simplest form, just video footage shown at a slower rate than it was recorded. This stretches time, making things take longer to happen on the screen than they did in real life. If you just slow down regular footage however your final video will be a jerky and unattractive, so we need to find a way to achieve that slow motion effect but with beautifully smooth-looking movement that looks effortlessly natural.

The Principles

Most video is recorded at 24fps, 25fps or 30 frames per second. For each second of action the camera records 24, 25 or 30 frames video. Long ago it was agreed that this many frames in every second of footage were required to make motion in a film appear natural on-screen. The exact frame rate you choose will depend on where you will show your film; 24fps for cinema, 25fps for TV in PAL regions or 30fps for TV in NTSC regions – though any of those will look fine on the Internet. As we are in the UK, and our region uses the PAL standard, I’ll take 25fps as my base for examples in this piece, but it isn’t hard to convert that to 24fps or 30fps.
If you record a 5-second clip at 25fps and play it back at 25fps it will last 5 seconds and any motion in the scene will look normal. If you play that same footage back at 50fps the clip will only play for 2.5 seconds and the motion will occur at twice the speed it did in real life – everything will be sped-up. If you play it back at 12.5fps the clip will last 10 seconds and the motion will be slowed down to half the speed of real life. The maths are pretty simple – 25/12.5=2, so with this scenario we’ll have 2x slow motion.

The problem with this situation is that footage played at 12.5fps will look jumpy because it doesn’t have the enough pictures to display in each second to create motion that looks smooth to our eyes. Footage played at 12.5fps might look like an old Charlie Chaplin film or a flip-book. To achieve smooth motion we still need to play our footage back at 25fps, so to get a slow motion effect we need to record at a higher frame rate in-camera so we can slow it down afterwards. To get successful 2x slow motion that plays smoothly we need to set the camera to record at 50fps.
The key to whether we can create slow motion video that looks good is to find a camera that will allow us to record at these higher frame rates.
Fortunately the Lumix series offers users a very good choice of cameras that can record high-frame-rate video of the sort that’s ideal for playing back at lower rates for fabulous-looking slow motion. All of the current Lumix G and S series cameras, and many older models, allow us to create at least 2x slow motion through their 48, 50 or 60fps recording settings.

High and variable frame rates

This is the list of codecs in the Lumix GH6, with the C4K 120p mode highlighted. With this option selected the camera will record 120 frames per second, which is many more than needed for ‘normal’ 25fps playback. With all those extra frames-per-second though, fast action will look very smooth when the footage is played back at 120fps. As this mode in is the regular list of codec options, and it allows audio and autofocusing, it is considered High Frame Rate video

Some Lumix models offer two approaches to recording at high frame rates – HFR and VFR options. HFR (High Frame Rate) are codecs with higher than usual frame-per-second recording rates which also allow recordings with audio and autofocus. VFR (Variable Frame Rate) modes don’t allow audio or AF, but they do allow a wider range of incremental recording frame rates, including frame rates that create fast motion. VFR also allows higher recording frame rates than HFR, so ultimately it can produce footage with a more dramatic effect.

Not all codecs offer Variable Frame Rate shooting, but when one does you’ll see ‘VFR available’ in the on-screen display. You then need to go back to main menu page to the Variable Frame Rate option and switch it on

Using the HFR mode is really a short cut for slow motion as it only involves choosing a codec with a higher recording rate than you will use in your final film – which is simple to do in the camera menu. Once the footage is slowed-down though the audio will be unusable, so you either need to delete it or detach it from the video file before you slow the clip so you can use it separately. Having autofocus can be very useful, which is another reason some users choose HFR options.
Really though HFR codecs are designed to be played back at their recording frame rates to create extra-smooth motion in the final picture, especially when that motion is rapid. There’s no reason not to also use them for slow motion effects.

This is the Variable Frame Rate control panel. You’ll see whether the option is switched on or not, and you’ll also see the details of the options you have selected and the effect they will have on your footage. Here a 240fps frame rate will play back at 10% of the original speed – so with a 10x slow motion effect

A HFR mode might be a codec such as 4K 50p that you intend to play back at 25p for a 2x slow motion effect. When you pick a codec that allows VFR you select the playback frame rate with the codec – such as 4K 25p – and then use the VFR menu to determine the final recording fps setting and to see the slow/motion effect expressed as a percentage in the display. When you play VFR footage back in the camera you get to see the effect immediately, as you do in your video editing software. HFR video needs to be manually slowed in post-production to see the effect otherwise it plays at the normal speed.

Creating slow-motion in post-production

How you deal with your clips as they are dropped onto your timeline depends on how they were recorded.

HFR:

You need to set the frame rate of your project as normal, which might be, for example, 25fps. Often when the first clip of a project is dragged to the timeline the editing application will ask if you want it to adjust the frame rate of the timeline to match the frame rate of the footage being imported. Usually this is a handy reminder and we allow it to go ahead, but when we are pulling in clips shot at 50 frames per second that we want to play back slowly we need the timeline frame rate to remain at 25fps – so don’t accept the suggestion of the prompt.