[davidmanze]

Apparently the lens was not the best example in well made firmware. There are a couple of firmware upgrades already available, see https://www.sigma-global.com/en/download.../firmware/

 

Lucky if one has a dock to update it.

 

I also suspect, the OS actually is working only in exposure mode, not in "keep the finder view steady" mode. I'm not sure if that can be changed via dock, but I think, I could change it in the 150-600 Sports custom settings. What happens if you take a picture @400 mm and 1/30 shutter speed? Blurred? More blurred than without OS?

   A half press of the shutter wakes up the OS, in viewfinder OS mode you would hear it humming,

   

in shutter only OS you are unlikely to hear anything as there's is "mirror/shutter/diaphragm/OS"....there and back covering the relatively quiet and brief OS action.

 

 Here, the  OS system is running at it's frequency, seemingly without any Gyroscopic compensation.

 

  Out of interest:     Modern gyros are extremely small "wafers of silicon shaped a little like tuning forks" they work on the principle that when they experience an accelerating force (or any movement) the thin wafer bends (due to inertia) and a voltage is produced.....(much like the old ceramic record pick ups).  With three of these gyros one in each plane and you have the ability to compensate in three dimensions. 

   It's been a real revolution in stabilization..gone are the old heavy spinning motors of the mechanic gyros.......... these have low current consumption, low weight and are physically very small........ they are mostly integrated within the surrounding micro circuitry.

 

   Stabilizing  the fourth dimension does of course require different techniques......and is better approached by chemical means!

 

   Actually, I've always wondered why stabilized binoculars have not become more popular, 6-8 times magnification is about the practical maximum magnification without OS, while some stabilized binoculars can be steady at more than 20 times magnification.