Capturing time

Screenshot of slow motion video of cork popping from bottle
(Screenshot at the 5:01 mark)

How in the world did this slow-motion video capture two moments at once?

The cork just coming out of the bottle—AND—the moment when the cork hits the guy’s face? (look at the shadow on his shirt, you’ll see the cork hitting his face)

How slow-motion video works

When you imagine video being recorded at 30 frames per second, you probably think there are literally 30 distinct full frames recorded every second.

Like, in one second, you hear 30 shutter clicks. Each click is a full frame. Kinda like a movie reel. Over one second, you’ll have 30 little images.

That’s close, but not entirely it. There are indeed 30 images. But those 30 images are not captured in an instant. That 1/30th of a second is not that exact moment. Each 1/30th of a second is actually a little PROCESS within that short moment.

For each individual frame in that 1/30th of a second, the camera records each frame from the top down. If you are recording a person swinging a bat, the head is recorded first, then the arms, then the torso, down to the legs. Then when it reached the bottom. The next frame starts from the top again.

If you’d like to see how this works in action, the SloMo guys on Youtube produced a wonderful explainer video. They show you how the shutter works inside a camera in high-speed photography with shutters going a fraction of a second at 1-2,000th of a second.

I made this animated gif from The SlowMo Guys video

The slowed the video down, so you can see how the shutter clicks at the various super-fast speeds. Notice how the shutter doesn’t capture the entire frame, but only a small section from top to bottom.

That little sliver of the shutter is capturing one a little bit of the image at a time. That sliver moves from top to bottom.

The coolest part from their video is when they recorded a champagne cork being popped right into some guy’s face. Ok, that premise is rather odd, but it illustrates the point perfectly. Here’s that image again:

At the middle of the frame, you’ll see the cork just popped out of the bottle. But then further down, you see the shadow of the cork hitting the guy in the face!

How did that happen? Remember, video frames are recorded from top to bottom. For this frame:

  1. The shutter recorded the man’s eyes first.
  2. Then the shutter moved down and recorded the bottle and cork.
  3. Next down the shutter captured the shadow of the cork on the man’s shirt.

In that little bit of time it took the shutter to capture this one frame, the cork started to pop from the bottle and then hit the man’s face. All in one frame.

Absolutely fascinating how one frame captures two moments in time.

Literally, in this one frame, you see a moment in time when the cork is just leaving the bottle. AND IN THE SAME FRAME, you see another moment in time when the cork hits the guy in the face.

It’s like time is mashed up into one image. We think of video as a continuous timeline. This happens, then this happens, then this happens. Everything flows, but there is a distinct timeline. One thing happens after another. Things don’t happen at the same time.

In this image, it appears that past and future are happening at the same time. When you understand how high-speed video is captured, you can start to comprehend how an image like this is created.

This is an example of a short-exposure photography representing time. On the other hand is long-exposure photography.

Long-exposure photography

Represent a very long period of time in a photograph. Keep the shutter open a long time, and you can capture a single point of light moving across the screen like it’s a line.

Someone used a cider can to capture eight years in a single photograph. The ethereal snapshot, recorded by a drink can left in an observatory for almost a decade, may be the longest-exposure image ever taken.

Regina Valkenborgh's photograph features 2,953 arcs of light

I love the notion of time being represented.

Here we have examples of two extremes. Capturing 8 years of time, and capturing a fraction of a second. In both examples, images showing the course of time.

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