Upload & Sell: Off
Well, the lens arrived, and it is exactly as I expected. Wonderful build quality, and fortunately, better wide open performance than the 400mm f5.6 version I used to own on the Nikon f-mount. Yet, it will not let the camera fire if it is stopped down at all...generating an error code about not being able to communicate with the camera body. Wide open it focuses very fast and is really a good lens. So, to determine if it will be sharp enough stopped down...I came up with an extremely low tech test. BTW...I do have high standards. Generally, on a telephoto, I expect to see individual feather barbs or rami, and not a blurred mess. Testing on birds will have to wait, but for today I shot this....
Here is the new f-ring I fashioned out of black cardboard, gaffers tape, and a box cutter
Here is a 100% crop with the lens wide open at f4 at 1/1250th second
Here is a 100% crop with the lens at between f5.6 - f8 at 1/500th second using my home made f-ring taped to the end of the lens.
As you can see...it is sharper stopped down
Side by Side view
I still want to try and get the lens re-chipped. I will try calling Sigma US, and UK Monday.