[stoppingdown]

First tests, a couple of days ago, with the Canon 6D borrowed from a friend of mine. Basically useless, because:

1. I had just a few minutes;
   
2. the day was grey and dull;
   
3. I've to re-skill about the long-lens technique (I haven't been practicing for a couple of years)
   
4. I had forgotten how annoying is a slapping mirror :-) for vibrations.
   

So, because of 3 and 4, most test shots were blurred. Indeed, a few ones weren't, and were absolutely badly focused. For a couple of days I was worried about having a broken lens. Then today I got the manual Sony/Canon adapter and at least I could retry with full aperture and manual focus. Now the achieved sharpness looks to be the one I expected. 

 

I can share three points so far about the lens:

1. with the Canon camera I had a very good, even though preliminary, impression about the AF speed - only by manually de-focusing and measuring the time to catch focus again; I didn't try moving subjects. It seems faster than my old Nikkor AF-S 300 f/4.
   
2. the manual focusing ring of the Sigma 150-600 is poor, as I expected having read some reviews: thin and a bit difficult to grip, and too "quick". Nothing that can't be fixed with some exercise, and in any case I think I'll seldom use manual focus with this lens, so a minor point. The "Sport" version, according to reviews, is much better in this respect.
   
3. the tripod collar is definitely bad. Placed too towards the rear end and probably too small. At 500mm you can see lots of motion in the EVF (not mentioning how long the vibration stays after a shot with a DSLR). I expected this too, by just looking at the catalog photos of the lens. And even the Nikkor AF-S 300 f/4 was bad in this respect: I had to work around it with a piece of rubber stuck between the foot of the collar and the lens; and later bought a replacement collar from Really Right Stuff. It was not just a dove-tail plate to adapt to Arca plates, but a global replacement of the collar with a longer foot and another support in the front where the lens could rest; in other words, the lens would rest on two supports.