A camera that shoots 40k FPS decided the 100-meter sprint final

How the finish camera works

• It’s a line-scan (strip) camera: the sensor is effectively 1 pixel wide and many pixels tall.
• The vertical axis is space across the track; the horizontal axis is time. Each vertical column is the finish-line view at a specific instant.
• Every pixel in the composite image lies on the geometric finish line; runners look “distorted” because different body parts are captured at slightly different times.
• Shadows, shoes, and limbs are recorded as they cross the line, just like torsos. Distortions (e.g., “ski” feet) are expected.

Advertising banner and calibration

• The “banner” with the Olympic rings and brand logo behind the runners is not a normal 2D sign.
• It’s a very narrow, one-pixel-wide vertical LED strip that rapidly cycles columns of the logo.
• To the naked eye it looks like flicker; to the line-scan camera, stretched over time, it becomes a readable banner.
• Commenters note this is both marketing and a quick visual check that camera alignment and timing are correct.

Timing, data, and FPS semantics

• The camera captures around 40,000 “lines per second,” which some argue is a more accurate term than FPS for a 1D sensor.
• Because each “frame” is only one column wide, data rates are manageable; RAM-based buffering with later SSD dump is considered sufficient.
• One estimate: at 10,000 px height and 24-bit color, 40k lines/s is on the order of 10 Gbit/s.
• Discussion contrasts this specialized setup with general-purpose high‑speed cameras and old film-based strip cameras.

Rules, fairness, and what counts as winning

• Officially the torso decides the finish, not “any body part”; detailed guidelines define where the torso begins/ends relative to shoulders and hips.
• Some question whether camera angle or occluded body parts (e.g., hidden shoulder) could bias results, suggesting overhead or dual-side cameras.
• Others note that major competitions already require at least two finish cameras on opposite sides.
• There is debate over whether ultra-fine timing (e.g., 0.005 s differences) reflects true superiority or just noise and luck.
• Some argue for coarser official resolution or accepting more ties; others insist the race’s purpose is simply to identify who crossed first, however small the margin.

Alternative technologies and limits

• Suggestions include lasers, digital transponders on the chest, or dense rangefinder meshes.
• Pushback: transponder accuracy is limited (e.g., centimeter-level), body orientation/lean complicates “center of chest,” and sensors can’t yet match the optical precision and interpretability of photo finish.
• Several note that track construction tolerances, wind differences by lane, and reaction-time variation already impose a fairness limit beyond timing precision.

Critique of the article and broader context

• Multiple commenters find the linked article shallow and marketing-driven, lacking explanation of strip photography, optics, calibration, lighting, and reliability considerations.
• Others share links and anecdotes about older strip cameras in racing, industrial line-scan uses, drift-scan astronomy, and extremely high-speed DoD cameras, emphasizing that the underlying technique is mature but still fascinating.