Shooting slow motion is now easier than ever. Many cameras being released now will shoot 60fps. They may only do it at 1080p, but they can do it. If your final project is 24fps, that means you can slow down 2.5x without losing a single frame. If you’ve got a camera that shoots 120fps or 240fps, then you can slow things down even further. With 1,000fps cameras for our phones on the way, we can go even more slow-mo crazy.
But how can you use slow motion effectively? This video from Simon Cade at DSLRguide goes a long way toward answering that question. Some of the tips are technical, and some are purely creative. The why is just as important as the how when it comes to using slow motion, if not more so. Because if you don’t have a good reason why you want to use it, then the how doesn’t matter.
The thing to realise about slow motion, is that as effective as it can be, it’s not good for every type of shot. For some shots, you don’t really notice a difference when it’s slowed down. For others, it’s just pointless. So, let’s look at those tips.
Movement is vital
If nothing’s really moving in your scene, nobody will notice that the shot’s even been slowed down. Good subjects are things like sports, liquids splashing, destruction & explosions. If there’s no real movement, slowing it down isn’t going to make a difference.
Understand the frame rates
It’s simple maths, really. If you’re recording at one frame rate, and playing back at a different frame rate, you just divide one by the other.
For example, if you’re recording at 60fps, and you want to play back at 24fps, you simply divide 60 by 24. This gives you the answer 2.5. This means that 1 second of realtime takes 2.5 seconds to play back.
If you’re shooting 240fps and playing back at 24fps, then, 240 divided by 24 is 10. Your 1 second of realtime footage takes 10 seconds to play back in slow motion. Or 1/10th the original speed.
Think about light
When you’re shooting more frames per second, you usually need to increase your shutter speed, too. 1/50th of a second shutters are fine if you’re shooting 24fps. But, if you go up to 60fps, it’s physically impossible to shoot at 1/50th of a second. If you go by the 180 degree shutter rule, you’re now up to 1/125th of a second for 60fps. For 240fps, you’re at 1/500th of a second.
Faster shutter speeds means you need more light to adequately expose your subject. This might mean bumping up your ISO, opening up the aperture, or simply turning on more lights. This can introduce other problems, such as flickering with certain types of artificial light. If you’re using all natural light, you might need to shoot at a different time of day to get the shot you’re after.
Slowing down time to intensify emotion
This is commonly done by ramping the speed down. That means, it’s a transition from realtime to slow motion. Applications like After Effects and DaVinci Resolve allow you to do this quite easily.
The technique is often used to intensify emotion, or to reinforce a reaction to something. But, it’s also become a little cliché, and is often used in comedic situations these days.
Making stunts seem more epic
This is a little related to the one above. Slowing down stunts in action movies makes them feel more intense. Bigger, heavier objects move more slowly, relative to our perspective. It’s a technique commonly used to make small fires and explosions seem like a huge raging inferno. It’s also used to make small pools of water seem like huge oceans.
Our brain thinks it knows how fast something should travel, and when it’s slowed down, we perceive it as being bigger than it really is. In the case of a person, it makes them seem larger than life. For a hero in an action movie, that’s a big psychological factor.
In a movie, slow motion is often used to show the death of important key characters. Red shirts, stormtroopers and other minions might just get a quick half second shot. But the important characters are often shown in slow motion to add impact to the scene.
Also, yes, sorry, Dumbledore dies.
Make it a part of the story
Slow motion was used quite extensively throughout Inception. It wasn’t just a creative choice here, though. It was actually a part of the story.
5 minutes in the real world gives you an hour in the dream
– Arthur (Joseph Gordon-Levitt)
To show the difference between what was going on in the dream and the real world, time had to be slowed down outside the dream.
This is one that isn’t going to apply to most of us. Most of us don’t have things going on at different speeds in reality. But, if that is something that is integral to the story itself, you can portray it visually with slow motion.
The sample clip that Simon provides for this one is interesting. Because it’s using slow motion for several completely different meanings. In the first three clips of this sequence, we see three things. A wide shot of Arnold walking out of the elevator in slow motion. To us, the viewers, we already know he’s the hero. The shot is looking up at him. This combined with the slow motion reinforces that he’s the hero.
The second shot shows Sarah’s reaction, also in slow motion. It’s the shock of seeing Arnold’s face has he turns around, and her whole world suddenly feeling like it’s in slow motion. You know, it’s the same kind of thing that happens when you drop a glass onto a concrete floor or a light stand falls over. If you’re watching it, it always seems to feel like it’s taking longer to happen than it actually does. Yet, you’re powerless to stop it.
It reinforces her shock and fear. We’re looking slightly down on her, too, as she starts to fall, suggesting weakness.
The third shot goes back to Arnold, but this time it’s a closeup of his face. Now we see things from Sarah’s perspective. This is what she was reacting to. It takes on a completely different tone, and the hero suddenly feels more sinister and threatening – even though we know he’s a good guy this time.
The whole sequence contains several more clips, but the slow motion effect on ever single one of them adds to the emotion and impact. It makes you see the whole scene in a completely different way than if it were all played back in realtime.
Think about sound design
When you slow down video, you’re also slowing down the audio. If you just take the track recorded by the camera, this lowers the pitch, and can feel very weird and distorted. Sometimes you’ll want to lower the pitch, but it often doesn’t have quite the impact you hope for. Because the audio’s recorded digitally, it also doesn’t always stretch out very well, either. Especially if it’s an extreme slow down.
Sometimes, even though the footage is slow, you want your sounds in realtime. Simply adding reverb to a realtime shot can often sell the effect. This happens all the time in TV shows that contain gunfire.
Don’t use it just because you can
This is a big one, and one I’ve seen popping up more and more lately. A lot of people are using slow motion just because they can, and not because it adds to their story.
Yeah it looks cool, but does it really have a purpose? Or does it just make your video take longer to watch or no other benefit?
Slow motion, while a bit of a cliché is still extremely effective depending on the situation. So, use it wisely.