Super High Speed Cameras | Shutter Speed, Frame Rates & Exposure
Photography is such a unique way of capturing light that, if done correctly, you could gather light in many many different and unique ways. And each one of them would look different even if you film the same subject.
Today, we are going to talk about the challenges and rewards of filming using a Super High-Speed Camera. A High-Speed Camera is defined as a device that is capable of shooting in excess of 250 frames a second. If you are a filmmaker yourself and often make videos, you do already know the importance of frame rates. The usual frame rates used to create ‘natural motion blur’ to mimic our human eyes are 24 or 30 (depending on the content). So you do understand that almost ten times the ‘usual’ frame rate would make a killer slow motion footage.
Persistence Of Vision
Recently, Gavin Free from the YouTube channel ‘The Slow Mo Guys’ discussed the challenges of filming using a Super High-Speed Camera. The entire channel, as you can already guess from its name, is dedicated to shoot stuff that happens quickly and then slow it down to a frame rate that humans can perceive. It is so odd to think that many of these things may happen to us on a daily basis; but even though they happen right in front of us, we never get to ‘see’ them for real. This primarily happens due to a phenomenon called Persistence of Vision.
Persistence of vision refers to the optical illusion that occurs when visual perception of an object does not cease for some time after the rays of light proceeding from it have ceased to enter the eye. (Wikipedia Definition)
In simpler terms, it means that we humans can only perceive things that are happening at a certain speed; anything faster than that and all we see is a blur with not much detail. For example, a bullet being fired, a piece of glassware breaking when it hits the floor or a hummingbird flapping its wings.
What really happens is, as these things happen at a brisk pace our eyes cannot keep up with it. You can think of it as the refresh rate similar to that of your computer’s screen. Our eyes and brain together refresh what it is looking at every 1/30th of a second (approx). This directly means that everything that happens within that extremely brief period is lost and cannot be seen by human eyes.
Movies and Animations
But don’t be so disheartened thinking that you miss all the ‘action’. Persistence of Vision is also the reason which makes all our favorite movies and animations possible. Back when the first animations were created, it was all hand drawn and colored. What you really saw on screen was all these drawings in a particular sequence….quickly!
With the advent of the DSLR & Mirrorless Cameras, we have really ushered into a totally new and modern zone.
In most of the cases, a few drawings per second. If this happened quick enough; our brain would magically join one image with the other and make it look like a smooth and languid video. This is exactly how we perceive our everyday life.
Now you know how many sketches it took to make your three minutes of Tom and Jerry cartoons.
Super High-Speed Cameras have come a long way but it really isn’t just pressing record and do weird stuff. There is a lot that goes behind the camera to make the footage look sharp and so dramatic.
Challenges Of Using A Super High-Speed Camera
Although shooting with a Super High-Speed maniac of a Camera sounds fun and adventurous, it is not always easy. The number one challenge that Gavin discussed was the eternal struggle with light. A Super High-Speed Camera shoots at astronomical speeds and frame rates. That is what they are built for. However, this also means that each frame gets very little time for exposure.
It is nearly impossible to shoot on a cloudy dark day; a sunlit day is a must. Moreover, for certain videos which are shot indoors, it requires a ridiculous amount of lighting to support such high frame rates. A wide aperture of the lens may help but not all the time since it also necessary to keep the subject in focus. Hence you will notice that most of the videos shot on a Super High-Speed Camera are shot parallel to the camera’s sensor plane. This allows the camera person to shoot wide and also keep everything in focus.
By the way, did you know that the shutter speed in these High-Speed Cameras is represented by an angle rather than a time period. This is a terminology that has been taken from the earlier days when the video cameras had a rolling shutter unlike the electronic shutters of the Phantom cameras that Gavin uses today.
I really think that many of the slow-motion videos do inspire ‘awe’. The let us see what we cannot with our naked eyes, and let us understand and marvel at the beauty of things in a totally different environment.
Author: Aalok Das