One Million Views: Photographer Freezes a Spinning Fan on Camera

A video experiment has passed one million views in days. Pavel Mamontov, the YouTuber behind the channel Lensevision, synchronized his camera with an ordinary desk fan until the spinning blades appeared frozen in place.

The demonstration rests on a principle called the stroboscopic effect. The idea is simple arithmetic. A camera recording at 30 frames per second will show a three-blade fan as completely stationary if the fan rotates at exactly 10 revolutions per second. Each blade slides into the position the previous blade held one frame earlier. The eye and the sensor together read the result as stillness.

The same principle explains why helicopter rotors sometimes look frozen or warped on film. It is not a trick of the fan. It is a collision between a mechanical rhythm and a sampling rate.

How did Mamontov build the shot?

Mamontov began by drawing a different symbol on each of the three blades. The symbols turn the experiment into a visible test. If the fan truly locks to the frame rate, the symbols stay put. If the fan drifts even slightly, the symbols swap positions from frame to frame, and the drift becomes obvious.

He controlled the fan's speed by hand. "I'm using a potentiometer to control the speed," Mamontov explains. "So the RPM keeps fluctuating, and I have to find just the right moment."

That hand-tuned approach produced an instructive failure. Early in the video, the blades themselves appear frozen, but the symbols keep changing. Mamontov explains the cause plainly: between two frames of video, "the fan rotates just enough for the next blade to take the place of the previous one." The fan looks motionless on camera while it is actually spinning at full speed. Because each blade carries a different mark, the swap betrays the rotation.

The takeaway: a matched frame rate creates the illusion, but only a precise match holds the image together completely.

Why did the blades appear to reverse?

The experiment then took an unexpected turn. As Mamontov adjusted the fan's speed, the blades appeared to reverse direction, spinning counterclockwise instead of clockwise. Slightly faster synchronization causes this reversal, the same mechanism that makes wagon wheels seem to roll backward in old films.

"By slightly adjusting the speed, you can even make the blade appear to move back and forth," he adds.

The takeaway: small changes in rotation speed flip the perceived direction of motion, which is the stroboscopic effect working in reverse.

What role does shutter speed play?

Mamontov does not reveal his shutter speed in the video. The technique matters regardless. A faster shutter reduces motion blur within each frame, and less blur makes the blades and their symbols appear sharper and more convincingly frozen.

A slow shutter lets each blade smear across part of the frame. The stroboscopic alignment still holds, but the image loses its crisp stillness. Shutter speed here serves the illusion rather than the exposure.

The takeaway: frame rate creates the freeze, but shutter speed decides how clean the freeze looks.

Did the experiment succeed?

Yes. Mamontov eventually locked the speed and captured the blades and their symbols holding the same positions across successive frames. He also notes that the solution is not unique. "There can be a whole lot of different speeds where the fan appears completely still," he adds, since any rotation that moves a blade a full integer number of positions per frame produces the same result.

The one-million-view count suggests a broad appetite for optics demonstrations that cost almost nothing to stage. Mamontov continues to publish similar camera experiments on his Instagram and YouTube channels, where the audience that made this fan video a hit will find his next test of perception.