Mystery Archive / Photographs & images
A bent propeller? Different capture times inside one photograph
A spinning propeller can look bent or broken in a photograph. Separate the object’s shape from the different times recorded across image rows.
First, what is puzzling about these propeller pictures?
A photograph of a fast-spinning propeller may show apparently bent or disconnected blades. It is natural to wonder whether the blades really took that shape. Rather than examining one viral image, this page isolates a capture process that can produce unusual outlines.
Some shutters expose all rows over the same interval. A rolling shutter offsets those intervals from row to row. An object that moves during the sweep can therefore contribute different poses to different parts of the image.
No propeller photograph is reproduced. We use a rigid two-blade bar and invented horizontal rows. Compare a shared reference instant with staggered row times, then reverse only the order in which the rows are sampled.
When an outline changes in a photograph, how can we separate a bent object from a difference in row capture times?
An object’s shape and its recorded outline can differ
Camera manufacturer Axis uses fast-spinning fans and propellers to illustrate rolling-shutter distortion. If exposure intervals shift between rows while the object moves, the combined outline may differ from the object at any one instant.
This does not identify every unfamiliar outline as rolling-shutter distortion. Interpreting a particular image requires its capture conditions and motion. Here we separate one mechanism rather than authenticate an unknown photograph.
Exposure duration and the offset between rows are different
Basler’s documentation describes successive row-exposure starts separated by a time offset. Each row may collect light for an equal duration while starting at a different time.
How long one row is exposed and how far apart the first and last row times are describe different quantities. A short exposure does not necessarily remove distortion from the remaining offsets during fast rotation.
Every instantaneous bar is straight; the recorded rows can differ
Shared row times
Staggered row times
The object turns clockwise in every comparison. Its bar stays straight at every instant.
The label electronic does not settle the question
The important comparison concerns when rows collect light. A global shutter can expose every row together, store the signals, and still read those signals out row by row later. Readout order alone does not define exposure timing.
FUJIFILM’s photography guidance also discusses rolling electronic shutters and fast motion. A description of one product is not a universal rule for every electronic camera. This activity does not rank camera models or equate electronic and mechanical labels with two fixed timing schemes.
First comparison: record one bar with shared or staggered times
The left card always shows the straight bar at the middle row’s reference instant. The right card combines the recorded rows. Try both All rows at one instant and Row times from top to bottom, comparing the two outlines.
The bar’s size, centre and clockwise rotation stay fixed. Only the assigned row times change. Check the top, middle and bottom row times in the table: they match in the shared-time mode and progress in the staggered mode.
- Assign times to the rows
The model selects either a shared reference instant or an ordered sequence of row times. This is a capture-process guide, not an invention chronology.
- The bar changes pose
Across invented time 0→1, the rigid bar turns clockwise through 120°. Staggered rows sample different poses.
- See the rows together
Rows from different times appear together in one image. Read their timing table alongside the combined outline.
Second comparison: keep rotation, reverse the row order
Stage two restarts with top-to-bottom sampling. Select both top-to-bottom and bottom-to-top. The bar continues the same clockwise motion, and the middle row retains the same reference instant.
Compare the recorded outline and the exchanged top and bottom times. You have not reversed the blades’ rotation. The aim is to distinguish the object’s motion from the order in which image rows record it.
The result establishes the invented rows’ time relationship
The model calculates the bar’s occupied interval at the centre of each invented row. Times from 0 to 1 indicate relative order, not seconds. It omits exposure integration, motion blur, a physical sensor and aircraft conditions.
Returning to a photograph, follow What an odd shape with How was it recorded? This model cannot establish a particular image’s authenticity, original blade count, rotation speed or camera model.
What if one motion is recorded in different orders?
Change the rigid bar’s recording scheme and compare its row-time table with the resulting outline.
Compare row capture timesSources and scope
Manufacturer documentation and direct explanations support the background: Basler for row exposure timing, Axis for spinning objects and the distinction from blur, and FUJIFILM for photographic context.
- 01Electronic Shutter Types Basler · Product Documentation · Checked 2026-10-22
- 02Global shutter vs rolling shutter Axis Communications · White paper · August 2026 · Checked 2026-10-22
- 03Electronic vs Mechanical Shutter FUJIFILM · X Stories · Checked 2026-10-22
The prose, bar geometry, row samples and timing table are original. No propeller photograph, drone shape, manufacturer diagram, logo or source layout is copied or traced. Row counts and numbers are model settings, not measurements from a camera.