Nikon 300mm pf VR issue possible explanation

micloi

micloi

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Michael
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I tried something that seems to shed some light to the VR issue that some people experience with the Nikon 300mm pf.

I tried 3 copied of the 300mm pf lens on many cameras and never had an issue with VR in low speeds as suggested from some reviews and forum members.

After a suggestion that mirror slap could be the issue on ungripped cameras (and especially the D810) I tried the test below which I was able to replicate.

The D7200 works ok at every speed with or without a grip.

ON THE OTHER HAND the D810 works ok with the grip (how I was always using it thus I never experienced the issue before) BUT as soon as I removed the grip the VR issue surfaced!

It seems like the mirror slaps at certain frequencies that affect the VR system of the 300mm pf on certain cameras (i.e. D810). The grip changes that frequency on the D810 and solves the issue.

D7200 GRIPPED:
https://dl.dropboxusercontent.com/u/16187250/Nikon 300mm pf/VR test/D7200 gripped.jpg
D7200 NO GRIP:
https://dl.dropboxusercontent.com/u/16187250/Nikon 300mm pf/VR test/D7200 no grip.jpg
D810 GRIPPED:
https://dl.dropboxusercontent.com/u/16187250/Nikon 300mm pf/VR test/D810 gripped.jpg
D810 NO GRIP:
https://dl.dropboxusercontent.com/u/16187250/Nikon 300mm pf/VR test/D810 no grip.jpg
 
Interesting observation. I can't recall where, but I recall reading about a photographer who recommended not only putting the camera on a tripod and firing with raised mirror using a remote trigger, but draping a small sand bag, such as a plastic bag of sand inside a sock, over the junction of camera body and lens, in order to increase mass and add some damping against vibration modes which shutter shock might induce. He claimed to have photographs which would show the advantages of his method to the determined pixel peeper. Thinking at the time that I didn't have this problem I didn't bother checking his images.

Of course he also recommended having the image stabilisation turned off. There are recent controversies in the Olympus community which suggest that combinations of certain bodies and lenses are liable to the exaggeration of shutter shock vibration modes by the image stabilisation. It's often forgotten, even by development engineers who ought to know better, that all PID type servo stabilising mechanisms have an inherent natural and unavoidable well damped resonant frequency. If a natural resonant frequency in the entire object (in this case camera plus lens plus grip etc.) approaches this servo frequency, or an integral multiple or fraction thereof (octave resonance), the performance of the stabilisation system can be seriously degraded because it contributes to perpetuating the oscillation.

People sometimes use image stabilisation on long lenses on a tripod in order to get image stabilisation in the viewfinder so they can manually trim the sometimes very trickily precise focus. Might be a good idea to try turning it off after focusing to see if this helps to improve image sharpness.
 
So this is not a VR problem directly, but rather more mirror/shutter shock that the VR has failed to correct, or has not been completely effective because the resonant frequency thing has exaggerated it? As a matter of interest, what were the shutter speeds and shooting distance? And could you replicate this result exactly with every shot? Thanks :)

It's also well known that image stabilisation systems are less effective with straight shift movements left/right and up/down (that could be happening here) as opposed tilting pivot-like movements. The latter is less problematic at normal shooting distances, but becomes more significant at close range. Canon's 100L macro was the first lens to address this with its Hybrid IS system.

I also have heard of a technique when using long lenses on a tripod, that is to rest the left hand on top of the lens (and/or place a sandbag) and hold the camera with the right, rather than letting it stand free and using a cable release, even when the camera is theoretically absolutely stationary. The human body is very good at absorbing and dampening vibration.
 
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micloi said:
Shooting distance was a few meters. Results are repeatable and were verified by another 2 people.
Click to expand...

micloi said:
Shutter speeds I tried were between 80 and 160. As reported already this is the affected range.
Click to expand...

Thanks. As I recall, around 1/100sec is the critical speed for shutter-shock with the Sony A7R* whereas with mirror-slap it's usually around 1/15sec or so that shows it up worst. Interesting, cheers :)

*Edit: with a lump of lead underneath being a cure.
 
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It's a nikon ,hitting it with a hammer works best :exit::woot:
 
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