In an attempt to ameliorate the a7R portrait-orientation vibration blur in the preceding post, I made two modifications to my setup. I cinched the lens to the support with a cable tie (shown before the ends were cut):
And I put a two-pound weight on the bottom of the camera:
The result was an improvement in the horizontal blur at 1/80 second:
but an increase in the horizontal blur at lower shutter speeds. In fact, the worst shutter speed became 1/30 second:
This is in line with what Joe Holmes has observed (here and here) in his much more extensive studies of shutter vibration moderation through added mass. It also fits with the principles that I (cribbed from experts and then) put forth in this and subsequent posts. More mass reduces high-frequency excursion, but in the absence of any change to the damping, it lowers the resonant frequency and thus allows the motion to persist for a longer time.
For comparison, the a7 image looks like this:
So the added mass means that the a7R shutter-induced vibration in portrait mode can be tamed to the point where the horizontal resolution is about the same as with the a7. The vertical resolution is, as in the previous post, much better in the a7R.
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