First, How Slow Motion Actually Works
Understanding the basic principle of slow motion is helpful for both properly following and bending the format’s rules, so bear with me for just a second. The film effect has its origins in overcranking—in the early days of film, camera operators literally cranked the film reel when shooting a scene. By cranking the reel faster, they saw their films projected more slowly.
Why? That’s where we get to the basic premise of slow mo. Slow motion captures a bunch of pictures very fast—at least 120 images per second, and often 300 or more. Meanwhile, video typically plays back at an eyeball-friendly 24-30 frames a second.
So when you play back those 300 fast images at the speed your eye is happy with, you have a huge excess of images. Your 300 images may have been filmed in one second of real shooting, but they will last for 10 seconds on screen—slow motion is born.
1. Shutter Speed
Our brain can not distinguish beyond 30 frame per second. By filming anything faster than that it can be put on a 30fps timeline and it will play back slower. For example, filming at 60fps is 2 times slower than real time.
The iPhone 6 shoots at 240 fps, is 8 times slower than real time. We filmed at roughly 500fps and 1000fps which is 16 and 30 times slower than real time respectively. To accomplish this without ghosting in the footage the rule is the shuter speed has to be double that of the frame rate. At 60fps you need to be shooting at 1/125th of a second, 500fps is 1/1000th of a second and 1000fps is 1/2000th.
As we found out first hand, if you’re shooting somewhere dark, you’re screwed. The faster the shutter speed, the more light you need to shine on the object.
For 1000fps with the shutter speed at 1/2000 you need a lot of light. What seems ok to the naked eye, won’t necessarily be bright enough when shooting slow motion.
It’s not as simple as turning on more lights because they can flicker. Some low quality LED panels have a pronounced flicker when footage is slowed down. You can see this example in the movies or old TV shows where a TV in the background is flickering because it’s light output is at the same or slower rate than the footage being filmed.
Because every moment will be played out in slow motion, movement in real time can might not be obvious when the shot is slowed down. For shorter clips it’s not always necessary to use a tripod, but for longer slow motion shots we recommend it for the best final product.
If you are shooting a with a very shallow depth of field the focus of a the shot is vital to it being usable. In this case using a tripod is importing, any slight movement in your hands or body could shift the camera and in turn the focus point without you realising it. With the camera locked away on a tripod you will have one less thing to worry about.
5. Tracking shot
To do a tracking shot, you’ll need the tripod to stabilise the fast movement. Why fast movement when you want a slow pan? Because everything will be slowed down. What will feel like a fast movement of the camera will slow down to the perfect speed. This is something you might want to practice and check in advance if you only have one chance to get the shot.
6. Shooting too much or too slow
Shooting slow motion footage takes up a lot of space. When a single second turns into 40, you need to have enough storage space on your camera and
In the same way you can shoot too much, you can shoot too slow. Somethings are going to be better at 240fps than they would be at 1000fps. Then again, this Slow Mo Guys video was filmed at 170,000 frames per second so maybe there is no such thing as too slow.
When editing slow motion footage you need to be aware you don’t overdo it. Less really is more (unless you are making an entire video about slow motion). You will have shot amazing footage but by using too much it can take away from the overall video. The aim should be to wow the audience and leave them wanting more, rather than the opposite feeling.
Good Luck !!!!