Slow motion, also known as slow-mo brings a whole new element to filming. Especially in the action world, where everything happens in a blink of an eye, slow motion really enables us to see things that we can’t otherwise, see ourselves.
In this article, I will discuss:
- What slow motion is and how it works
- How to shoot slow motion
- How you can use your action cam to film
- Some editing apps you can use
What is slow motion?
Normal footage being played at a slower speed, like the video above.
Unlike time-lapse, slow motion only work with some cameras as it has to hit a bare minimum frame rate of 48 fps to be able to produce a smooth slow mo video.
There is actually a youtube channel called Slow Mo Guys, which specialises in filming slow motion videos on about everything that they find interesting. Do check them out as it is really cool and fascinating to watch what we see every day but 1000x slower than real time!
How does slow motion work?
To start explaining, you’ll need to know what frame rates are.
What are frame rates?
Frame rates which are expressed in frames per second are the frequency of which the frames in any video film are displayed.
To me, it is kind of the same as shutter speed (used in photography instead of videos) as both frame rate and shutter speed decides how fast the sensor is exposed to.
Every video that you have watched in your entire life are made up of images played consistently, at a very fast pace of about 24 frames per second to create an illusion of movement. Therefore, the higher the frame rate, the smoother the video will become.
There are 2 methods of how you can attain ‘slowed’ down film, of which, the first is more popular than the second.
1st Method – Overcranking
This is the more popular and efficient technique of the two.
It works like this.
As you know, videos consist of taking frame very quickly so that when played back, it is smooth and real life.
Normal movie and videos usually play at about 24-30 fps. Hence if you slow down a normal video by half, it would only be able to play at 12 – 15 fps, which is way too choppy and rough.
However, if instead, you decide to over crank and film at say 48fps, even if you slow down by 2x, it would be 24fps, which seems perfectly normal and still look smooth to the eyes.
Therefore, for this method, you would have to capture at a rate much faster than playback so that when replayed at standard real-time speed, the video will still be slowed down yet remain smooth at the same time.
2nd Method – Time stretching
This is what some call fake slow motion as it is a post production technique.
What it does is it fabricate a new frame from the preceding original frames. The frames that are made are then used to insert in between the original frames.
Most of the times, the frames are made by the digital software tracking motion from the preceding and succeeding frames. The fabricated frames are then generated which basically acts as a smoother for a better transition between the original frames.
However, as you might already know, this requires expensive software and is used much more in the past. Since cameras with slow-mo capabilities are so affordable and ubiquitous nowadays, I really do not find a point purchasing an expensive software (such as Twixtor) just to do that as they can cost as much or more than a camera capable of filming slow mo.
Pros and Cons
After reading all of this, you might think, why isn’t a higher frame rate, capable of producing slow motion, used in all videos and films since it is smoother and more pleasing to watch?
Well, as you know nothing is perfect and using slow motion or filming at higher frame rate too, comes with some drawback.
As you know, slow motion creates a smoother video as it captures it in higher frame rate, causing the transition between the frames to appear more realistic and smooth.
You can easily tell the difference if you go to Youtube now and watch the first half of any video in 720p 30. Afterwards, watch the same video again in 720p 60.
You would be able to immediately tell the difference. If you had the choice to watch either, I’m sure you’d definitely pick the one with higher frame rate because it is more smooth and pleasant to watch.
You can also take a look at this video to see the differences between 30fps and 60fps.
Note: Set the resolution to 60fps to see the difference.
As I mentioned earlier, filming at a high frame rate has some drawbacks too.
Because when filming with a higher frame rate, the light entering and being captured by the image sensor in every frame is going to be lower due to the exposure time of the sensor being shorter.
Hence, when filming at a high frame rate, it is important to have a bright enough lighting when filming. If you have a smartphone, you can immediately see the difference of the lighting when switching between slow-mo mode and normal video mode.
Lower Video Quality
Another thing you would notice is that it usually drops in quality when you enable slow mo.
If you see the settings in most action cam, the higher the frame rate and the lower the resolution.
This is because, when filming at a higher frame rate, it requires more processing power by the chipset (motherboard).
So for example, if your camera can film 4K at 30fps, it’s highly likely that it cannot film 4K at 60fps but at a lower resolution like 2.7K at 60fps.
Apart from the quality dropping, it is also possible that the field of view of your film decreases as well.
More Storage Space
Another thing about filming at higher frame rate is they take way more storage space.
I actually did a little test to see how much more it takes.
The one with 60fps actually took 1.5x more space than the 30fps video despite having the same duration and content!
Hence, do check if you have enough memory and plan accordingly if you wish to film at a high frame rate.
Scam: Fake Slow Motion
Many of the times, manufacturers can also trick buyers like you, that their camera can film at both 1080p 60fps although the specifications of the camera only allow at maximum, 1080p 30fps.
How They Do It
They program their camera to film at 720p at 60fps (camera is able to).
However, when you take a closer look, you’ll realise that it is very blur and unclear and resembles more of a 720p video.
Preventing From Happening
So how can you prevent yourself from getting scammed?
Well, the easiest way is to search for the camera’s reviews, forums. Simply comment down and ask the author if he knows.
Else, if you still can’t find it, feel free to contact me or drop a comment down below to ask me!
What is the best frame rate for slow motion?
If you are wondering about the best frame rate for slow motion, there is no best. As mentioned above, too high and the video would be very dim, too low and it would be too rough.
It all depends on your needs but most of the situations, I’d recommend 60fps for slow motion as the most balanced frame rate (brightness vs smoothness) to go with.
How to Film Slow Motion
Using Action Cams with No Slow Motion Mode
If you are wondering how you can film slow mo, you can easily change the settings in ‘Resolutions’ to capture any resolution at a frame rate higher or equal to 60 fps.
However, if you own another kind of camera or phone, you would have to look for the frame rate/resolution settings. If you wish to use it in a smartphone, just look for the ‘slow motion’ mode in your camera app.
Using Action Cams with Slow Motion Mode
Some cams have a slow motion mode on it and you can easily use it.
The difference between this and the one above is that it will produce a slowed down video but most of the time still requires additional editing as the whole video.
More will be explained below on how you can convert your videos to slow motion.
How to shoot in slow motion?
There are 2 ways you can achieve slow motion videos using a slow motion compatible camera.
1. Camera produces processed video (Has slow-mo mode)
Action cams (such as Git2) and most smartphones have the ability to customise your slow mo settings and to directly output slow motion videos, hence, all that’s left to do is select and trim the video to the highlights of your footage.
2.Camera does not produce slowed down video (No slow-mo mode)
However, truth to be told, most action cams only film at the frame rate which you set and do not output a slow motion video.
Hence, some editing is required.
For that, I have actually handpicked some of the best software for converting your videos