Laser pointer filmed at 2 billion fps.
Full comment
OT video: "A laser pointer at 2 billion fps makes the speed of light look... kinda weird" (2025; AlphaPhoenix) this video
A laser pointer at 2 billion fps makes the speed of light look... kinda weird
6M views · Oct 17, 2025 · 29:22 · 0 HN recommenders · 3 mentions · discussed 2025–2026
AlphaPhoenix shows off a new camera that films at two billion frames per second and uses it to film a laser pointer pulse. He investigates a strange quirk in how the speed of light appears on camera.
Why Hacker News points people here: Referenced in threads about the two-billion-fps camera and equivalent-time sampling as an example of filming light moving.
What Hacker News said 3
Equivalent-time sampling used to film light in a garage.
Full comment
By definition, you can't interpolate a sample. A sample is a measured value. What you can do, if and only if you have an exactly repeating signal triggering at the same point within a cycle, is change the delay between the trigger and sample, and repeat. In other words, sample at different times within the same signal (since it's exactly repeating), to build up samples in time, of that waveform, to whatever time resolution you want. Of course, you're limited to any noise in the trigger, variation in the signal, etc. This is how you can record light moving through your garage [1]! [1] this video
Filming light at 2 billion fps with single pixel.
Full comment
Related - filming light at 2 billion fps with a somewhat similar setup in concept (at the single pixel scale): this video