My Trip to Sigma
Not having anything else to go on to solve my focus issues with the Sigma 120-300 f2.8 “Sports” lens and the Canon 1D, I decided to make the trip to Ronkonkoma Long Island. My hope was an in-person dialog with the service department as they looked over my lens would get to the bottom of things.
First off, they were able to un-stick the front filter, swapped my emergency replacement brass tripod collar screws with nice standard Phillips head screws, and assured me everything was fastened in with Loctite. Then it came down to making adjustments in the PCB ROM not available using the USB dock.
It was interesting to find out that the dock actually provides more control over the focus adjustment of the lens than the factory adjustment software. The factory software apparently allows + and – adjustments to just the outer focal lengths (120mm and 300mm). Based on my earlier findings they programmed some additional “+” into the 120 end and some “-” into the 300 end. The goal was hopefully to lessen the large gap in the settings from +17 at 200 and -16 at 300.
To make a long story short, it didn't work. The reprogramming had no real effect on the 300 side, and just shifted the required existing settings over a proportional amount on the 120 side. The main problem of not getting accurate focus with the 1D Mk IV (and Mk III) in between 200mm and 300mm was still the same. Next they brought out another new 120-300 “Sports” lens to compare with mine. The results were the same with the new lens, so that confirms it's not some anomaly with my cameras. With that the service manager said he would be sending an advisory to their headquarters in Japan to have them investigate it more.
So was it a wasted trip? I guess I will have to wait and see if I get an answer back from Sigma Japan. I also don't think just shipping my lens to them with the Mk IV (and being without both for a week or more) would have convinced them as easily that there really is something to all this. I will say that I was very satisfied with the service and reception I got while I was there, despite the outcome so far. I'm keeping my fingers crossed.