Vibration of the A7R shutter compared to D3 and NEX-7 using a seismometer

Started Dec 20, 2013 | Discussions thread
DavieK Contributing Member • Posts: 708
Re: Harmonics?

Bob Janes wrote:

Do you think that the problem of the excess vibration might be due to harmonics between the vibration of the initial closing of the shutter prior to exposure and the impact of the first curtain hitting the other side of the shutter when fully open? I notice the big peak on the Z axis occurs at about the 4th phase after the initial vibration... makes me wonder if the vibration would be minimised if the two impacts were out of phase rather than in phase with each other...

I think you may have something there Bob. Elsewhere I've quoted the transit speed of the shutter (4.8 metres per second) based on 24mm traversed in 1/200th - the time it takes for the first curtain to fully uncover the sensor, equal to the flash sync speed (where the second curtain starts travel after 1/200th).

The seismic readings indicate that the peak/tail occupies half of a 1/100-1/125 or similar exposure time, which would be commensurate with two vibrations ending in in phase - one from the capping action of the first blind, the second from its closing end of travel.

David

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