D3 shutter: Within the blink of an eye

Started Sep 2, 2008 | Discussions thread
OP Marianne Oelund Veteran Member • Posts: 7,788
Some numbers
1

Speed and Precision

Using the timing information, one can plot the shutter curtain displacement versus time, and estimate velocities and accelerations.

Total transit time for the curtain edge to cross the height of the sensor is only 3.0msec. The shutter curtains reach a peak linear speed of 10mm/msec during the second half of their transit, which is 10m/sec or 36kph (or over 22mph for those of us still using Imperial units). That's significantly faster than most people can run.

In order to achieve that speed, an acceleration of at least 500g's is required to start the curtains moving. At the end of their movement, they come to a stop in only 0.5msec, which is a deceleration of at least 2000g's!

To make matters even more difficult for the designers, consider the precision required at high shutter speeds. At 1/8000 sec. shutter speed, the second curtain is released only 125microsec after the first curtain. In order to achieve a tolerance of, say, 1/6 stop, that time gap must be maintained within 15microsec, which is only 0.5% of the shutter transit time. So not only must the curtains perform the high accelerations, they must do so with a speed error of a fraction of 1%.

All of which should give us pause, and renewed appreciation of what our cameras do every time we press that shutter release.

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