They say a picture is worth a thousand words, and by that logic a video must be worth millions. However, from nearly the dawn of photography around 1840, photographers have made fake photographs. In modern times, Photoshop and Deepfake make you mistrust images and videos. [Action Lab] has a great camera trick in which it looks like he can control the speed of light. You can see the video below.
You probably can guess that he can’t really do it. But he has videos where a real laser beam appears to slowly move across the screen like a laser blaster shot in a movie. You might think you only need to slow down the video speed, but light is really fast, so you probably can’t practically pull that stunt.
The trick is to build a chopper that interrupts the light beam. The spacing of the aperture and the speed will control how the light appears. Of course, that doesn’t do anything unusual if you are just looking at the scene. The laser beam appears and then disappears as normal, seeming to travel instantly.
The trick is in how a digital camera takes a picture. The scan rate is fast, but the light is faster. So even though the laser traverses the frame all at once, the camera may only capture a piece of it. By controlling the scan rate and the rotation of the chopper, you can make different effects pretty easily. The video took inspiration from an earlier video that you might also enjoy.
Sure, you could add the laser shots digitally later. But the fact is, the laser bolts look real because — well — they are. In both videos, you can see people interacting with the beams and it makes it really clear that it isn’t a special effect or, if it is, it is a really good one.