# Photon Film (DD-067)

> In 2020, Edoardo Charbon's AQUA lab at EPFL and Canon unveiled MegaX, the first megapixel camera built from single-photon avalanche diodes (SPADs), pixels sensitive enough to register one photon at a time. It records up to 24,000 frames per second, but it can also open its pixels for gates just nanoseconds long and shift them in steps of picoseconds (trillionths of a second). Repeating a laser pulse and stepping the gate let the team rebuild a laser pulse flying past optics, slowed down hundreds of millions of times. The 'trillion frames per second' figure the Reel uses belongs to other projects: MIT's 2011 femto-photography and Caltech's 2018 T-CUP, which reached 10 trillion frames per second.

- Department: Tech (also Science)
- First published: 2025-11-01
- Last updated: 2025-11-01
- Permalink: https://detailenjoyer.com/case/photon-film/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## On the timeline

- **2011**: MIT's femto-photography films light at an effective rate of about a trillion frames per second
- **2018**: Caltech's T-CUP reaches 10 trillion frames per second in a single shot
- **2020**: EPFL and Canon unveil MegaX, the first megapixel SPAD camera
- **2021**: EPFL's team reconstructs a laser pulse moving through space in 4D

Full timeline: https://detailenjoyer.com/timeline/?case=photon-film

## Quick facts

- **DD-067-F01**: EPFL and Canon's MegaX, unveiled in 2020, was the first megapixel camera made of single-photon avalanche diodes. _(Write-up · Exhibit A (What EPFL built))_
- **DD-067-F02**: MegaX records up to 24,000 frames per second; trillion-frame-per-second results came from MIT (2011) and Caltech (2018). _(Write-up · Exhibit E (Where 'trillions' comes from))_

## Write-up

A camera that films light itself moving. EPFL's MegaX catches single photons and rebuilds a laser pulse in flight from many repeated shots.

1. **What EPFL built**: MegaX, from Edoardo Charbon's AQUA lab at EPFL with Canon, was the first megapixel SPAD camera, the result of about 15 years of SPAD research. It was described in Optica in 2020.
2. **Single-photon pixels**: Each pixel is a single-photon avalanche diode. One photon can trigger a measurable avalanche of current, so the sensor counts individual photons. That doesn't mean you see a single photon flying across the frame.
3. **Fast, but not trillions**: MegaX shoots up to 24,000 frames per second. To film light, the team opened its pixels for a 3.8-nanosecond gate and stepped it in 36-picosecond increments, building the video from many repeated laser pulses.
4. **Light in flight**: In a 2021 paper, the team used the camera to reconstruct a laser pulse moving through space in 4D, using machine learning and an effect called apparent superluminal motion.
5. **Where 'trillions' comes from**: MIT's 2011 femto-photography captured light at an effective rate of about a trillion frames per second using a streak camera and repeated pulses. Caltech's 2018 T-CUP reached 10 trillion frames per second in a single shot by encoding the scene with a pseudo-random pattern.

## Related case files

- [Cherenkov Glow (DD-020)](https://detailenjoyer.com/case/cherenkov-glow/): More light doing something strange: the blue glow of particles outrunning light in water.
- [Shrinking Circuits (DD-018)](https://detailenjoyer.com/case/shrinking-circuits/): MegaX is a chip with a million single-photon pixels; this case follows how chips went from four transistors to 80 billion.
- [Solar Sailing (DD-039)](https://detailenjoyer.com/case/solar-sailing/): Photons again, this time carrying enough momentum to push a spacecraft.
- [Alcubierre Drive (DD-060)](https://detailenjoyer.com/case/alcubierre-drive/): The speed limit, bent on paper: a warp bubble that outruns light only as seen from outside.
- [Video Trickery (DD-301)](https://detailenjoyer.com/case/video-trickery/): I linked more about how cameras capture light
- [UV Face (DD-654)](https://detailenjoyer.com/case/uv-face/): Another camera that sees light human eyes can't
- [HoloFans II (DD-700)](https://detailenjoyer.com/case/holofans-ii/): Another case about light and imaging hardware

## Reel vs. record

- **Confirmed**: EPFL did build a SPAD camera that filmed a laser pulse in flight. MegaX, developed with Canon, was the first megapixel SPAD sensor (Optica, 2020). [EPFL; Morimoto et al.]
- **Wrong speed**: MegaX isn't a 'trillions of frames per second' camera. It records up to 24,000 fps; the light-in-flight video comes from 36-picosecond gate steps over many repeated pulses. [EPFL; Phys Rev X 2021]
- **Overstated**: it doesn't let you watch individual photons. Each pixel can detect one photon, but the movie is rebuilt statistically from countless photons scattered over repeated pulses. [EPFL; Phys Rev X 2021]
- **Mixed up**: 'encoding each light pulse with unique temporal patterns' sounds like Caltech's compressed ultrafast photography (pseudo-random spatial encoding), not EPFL's time-gating. [Liang et al. 2018]
- **Credit where due**: trillion-fps imaging of light dates to MIT's 2011 femto-photography (about 0.5–1 trillion fps effective), and Caltech's T-CUP hit 10 trillion fps in 2018. [MIT News; Velten et al. 2013; Liang et al. 2018]

## Video: Photon Film: A Camera That Films Light Itself Moving

- Duration: 21.4 s · Published: 2025-11-01
- File: https://detailenjoyer.com/assets/videos/DQiE9NdERcT.mp4

### Transcript

DID YOU KNOW? Swiss scientists at EPFL developed a groundbreaking camera capable of capturing the motion of light at trillions of frames per second, fast enough to observe individual photons in action. Using advanced single photon avalanche diode sensors, combined with computational imaging techniques, the camera can reconstruct ultra-fast events by encoding each light pulse with unique temporal patterns. NOW YOU KNOW!

## Questions & answers

**Q: Which company partnered with EPFL on MegaX?**  
A: It came from Edoardo Charbon's AQUA lab. _(Source: Write-up · Exhibit A (What EPFL built) · MegaX: the first camera to capture the smallest particles of light (EPFL News, 2020); Morimoto et al., Megapixel time-gated SPAD image sensor for 2D and 3D imaging applications (Optica, 2020))_

**Q: What does a SPAD pixel detect?**  
A: One photon triggers an avalanche of current. _(Source: Write-up · Exhibit B (Single-photon pixels) · MegaX: the first camera to capture the smallest particles of light (EPFL News, 2020); Morimoto et al., Megapixel time-gated SPAD image sensor for 2D and 3D imaging applications (Optica, 2020))_

**Q: What is MegaX's top frame rate?**  
A: The light-in-flight video came from picosecond gate steps. _(Source: Write-up · Exhibit C (Fast, but not trillions) · MegaX: the first camera to capture the smallest particles of light (EPFL News, 2020); Morimoto et al., Superluminal Motion-Assisted Four-Dimensional Light-in-Flight Imaging (Physical Review X, 2021))_

**Q: What did the 2021 paper reconstruct?**  
A: It used machine learning and apparent superluminal motion. _(Source: Write-up · Exhibit D (Light in flight) · Morimoto et al., Superluminal Motion-Assisted Four-Dimensional Light-in-Flight Imaging (Physical Review X, 2021))_

**Q: Which lab reached 10 trillion frames per second in 2018?**  
A: Its T-CUP system works in a single shot. _(Source: Write-up · Exhibit E (Where 'trillions' comes from) · Trillion-frame-per-second video (MIT News, 2011); Velten et al., Femto-photography: capturing and visualizing the propagation of light (ACM Transactions on Graphics, 2013); Liang, Zhu & Wang, Single-shot real-time femtosecond imaging of temporal focusing (Light: Science & Applications, 2018))_

## Sources

- [MegaX: the first camera to capture the smallest particles of light (EPFL News, 2020)](https://actu.epfl.ch/news/megax-the-first-camera-to-capture-the-smallest-par/)
- [Morimoto et al., Megapixel time-gated SPAD image sensor for 2D and 3D imaging applications (Optica, 2020)](https://doi.org/10.1364/OPTICA.386574)
- [Morimoto et al., Superluminal Motion-Assisted Four-Dimensional Light-in-Flight Imaging (Physical Review X, 2021)](https://doi.org/10.1103/PhysRevX.11.011005)
- [Trillion-frame-per-second video (MIT News, 2011)](https://news.mit.edu/2011/trillion-fps-camera-1213)
- [Velten et al., Femto-photography: capturing and visualizing the propagation of light (ACM Transactions on Graphics, 2013)](https://doi.org/10.1145/2461912.2461928)
- [Liang, Zhu & Wang, Single-shot real-time femtosecond imaging of temporal focusing (Light: Science & Applications, 2018)](https://doi.org/10.1038/s41377-018-0044-7)

## Cite this case file

Easterling, Marcus. "Photon Film." The Detail Department (DetailEnjoyer), case file DD-067, last updated Nov 1, 2025. https://detailenjoyer.com/case/photon-film/