How can themeparks snap a crystal clear picture of you on a rollercoaster going 70mph
In: Technology
Three things:
1. They use fast shutter speeds. That means that the shutter is only open for a very short period of time to gather data. And during that short period of time, you don’t move much. Imagine you took a video at 3200 frames per second, then advanced it frame by frame. The movement would be almost imperceptible. That is how much you move while the shutter is open. They probably shoot at 1/3200th or even 1/6400th. The down side to having the shutter open for such a short period is that there is not much light that gets through in such a short period of time, so…
2. They use bright, fast flashes. That flash will pulse with each shutter click and it will be timed to illuminate the riders for the same length of time. So the riders are getting hit with a very bright light for only 1/3200th of a second and anything that happens outside of that window is too dark to really process.
3. They use angles to their advantage. Look out the side window of your car on the highway and things will be zooming by and you can’t really focus on them. But look out the windshield and you can easily focus on approaching items.
Cameras have a depth of focus. These particular cameras are set to focus on a point in space that is let’s say…3 feet deep. So as the riders are approaching the camera from the background toward the foreground, they will remain in focus for 3 feet as they pass through the camera’s view. In 1/3200th of a second, they will probably move less than a quarter of an inch. So there is plenty of time to capture them in focus.
But if that camera were placed perpendicular to the coaster train and shooting from the side, the riders would zoom through the view much faster. It’s the difference of trying to catch a baseball thrown toward your face and trying to catch a baseball thrown *past* your face from the side. It’s much easier to see it coming straight on.
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