My Sigma 17-70mm C zoom does not focus properly at longer distances. I had sent twice to their UK service for adjustment and they sent it twice to Japan....which left me without lens for 2 months and the focus problem remains unsolved at full aperture. I finally bought the Sigma USB dock and did the firmware update. Beyond that I'd like to tackle the focusing issue but all I get on the computer is diagram for adjustments without any instructions. Does any forum member use this accessory successfully?

Thank you Daron and John. Daron, the length of your comment seems to express the level of your frustration.

I had to send older bodies for post-warranty repairs and in both cases sent them to the official Pentax service provider in ... Germany. It worked well, just a few additional pounds for postage. The bodies came back in ca. 10 days after approval of the repair cost forecast, as far as I remember.

In fact I bought this grip second hand and it worked perfectly when I received it. Problem is, the vendor didn't send me a copy of the invoice which is needed for a the warranty.

My grip stopped working on tis second day. The aperture control works but none of the other controls. I tested with several batteries of course. Any clue on the cause?

You may want to look at the huge collection of Michael Freemann's books. From all-in-one to technically very detailed books on specific subjects.