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Longest known exposure photograph ever captured using a beer can
mag_therm:
But that T-Model photo was on the RB67 with a leaf shutter which is concentric.
I might have photo-diode traces of the penumbra and open-time somewhere of that or a similar RB67 lens.
I will try to find tomorrow and put up here if so.
The camera was hand held.
I do not understand the trajectory that the spokes make.
Anyway, sorry to have hijacked the good pin-hole thread.
helius:
If it was a focal-plane shutter effect, the whole wheels including the rims would be bent, as seen in Henri Lartigue's 1912 shot of the Grand Prix. This amazing picture also shows distortion of the crowd in the background, because the photographer panned his camera to track the car during the exposure (but slower than the car itself).
That effect happens as the position of the wheel in the picture changes during the exposure, enough to be recorded at a different position by the shutter opening as it scans from bottom to top. (The effect only works if the shutter curtains move vertically, so that the wheel and shutter motion are perpendicular to each other.)
In your picture, the shutter moves concentrically, but that is also perpendicular to the direction the spokes move, which is rotatory. So the bending effect looks different, but is caused by the same phenomenon.
mag_therm:
Hi Helius,
I agree that the falling slit focal plane shutter ( Like the Speed Graphic above) exposes the bottom of the image first (upside down on film),
and takes time to get to the top, which causes the "race car" distortion of the car leaning forward.
In the concentric leaf shutter, if considering the optic (ray tracing) the mode is quite different.
The shutter opens as the smallest pinhole.
The light at that time exposes the whole film plane, as Bravo's example in post one shows.
As the leaf shutter continues to open to the aperture setting ( I would have used F11) ,
the light intensity increases over the whole film frame, then reverses as it closes.
So there are no shutter "slit effects" where the timing of the exposure varies over the film plane.
Exposure all happens simultaneously with a leaf shutter.
The spoke outer ends near the ground are almost stationary, while the spoke ends at the top are moving at 2 X the car speed.
That effect is observable on the T-model.
But I can't understand why the spokes moving vertically, in front of , and behind the axle, are both tilted downward.
SilverSolder:
There could be an effect of incident light (or lack of light, e.g. a cloud or a tree or a building) getting reflected differently in the spokes as they rotate?
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