Why do bicycle spokes look bent in a photo-finish image?
Asked 8/27/2017
97 views
2 answers
0
In a close cycling finish photo, the wheels and spokes appear distorted: the spokes look bent, and even the rim holes seem shifted. It looks similar to the way airplane propellers can appear warped in some photos. What photographic effect causes this, and why does it happen in photo-finish images?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
8
Photo-finish photographs are made using slit-scan cameras, not conventional cameras. The left to right relationships in the image are temporal rather than spatial...the distance in the image between the front and the rear of each bicycle reflects the amount of time between the front and the rear of the bicycle crossing the finish line (and passing in front of the slit).
The bending of the spokes reflects the different times at which the spoke crossed the finish line and was captured through the slit. The entirety of the hub of the wheel crosses the line in a shorter amount of time than the circumference of the wheel.
Originally by user50888. Source · Licensed CC BY-SA 4.0
user50888
9y ago
0
Generated from our catalog & community — verify before relying on it.
The spokes are not actually bending. This is a time-based imaging effect.
In true photo-finish photography, the image is usually made with a slit-scan camera rather than a normal full-frame exposure. The camera records only a very thin vertical slice at the finish line and builds the final image over time. That means left-to-right position in the picture represents when something crossed the line, not its real shape at one instant.
Because different parts of a rotating wheel pass the finish line at different moments, the spokes are recorded at different times as the wheel turns. This makes straight spokes appear curved or slanted, and can also make rim details like drilled holes look displaced.
A somewhat similar distortion can also happen with focal-plane shutters or rolling capture, where different parts of the frame are recorded at slightly different times. But for a race finish image, slit-scan capture is the main reason.
So the photo is not showing physical bending; it is showing motion over time mapped into a single image.
Recommended products
UniqueBot
AI9y ago
Your Answer
Related Questions
Why did my airplane-window photo show psychedelic colors over dark water?
Why do my close-up photos suddenly look wide or distorted on my Sony Cyber-shot?
Why can polished watch hands and markers look black in product photos?
Can a bird's head look distorted in flight because of angle, or is it likely photo editing?
Is the curved floor in a wide panorama caused by parallax error?