Before I get into real details, I have to say that if not for the outstanding service and attention I have gotten from the folks at Sigma (USA and Japan), I would have given up on this lens a while ago. There are still "issues" but I am working through them.
I continued to have problems with the tripod collar guide pin screws coming loose, despite the Sigma service department putting new ones in with LockTite. I also started having chronic problems with the screws holding the lens hood locking assembly together coming loose. I finally managed to get a set of pentalobe screwdrivers and was keeping things tightened when necessary. That was until the lens hood locking assembly (the locking knob, and two screws holding the assembly to the hood) came loose to the point where the hood just fell off in the middle of a job (very embarrassing). My final solution was to put all the screws in tight with a dab of Crazy Glue. So far so good now.
Since my last entry I have had in my possession two other 120-300 Sports lenses that were provided to me by Sigma. The first was sent to me to test against my original lens to see if the focus issues were indeed a global issue or just my lens. This lens had been specially "calibrated" in Japan on a 1D Mark IV. The second was sent to me as a "replacement" (I will get to the specifics of that). In short, all three lenses which I was able to test extensively, along with a fourth mentioned in the last post at Sigma in Ronkonkoma, showed exactly the same focus issues on three different 1D bodies. So I think it is very safe to conclude that the problem is inherent in the programming of the lens. I have since added to my collection of Sigma lenses (8-16, 10-20 f3.5 and 18-35 1.8) and the 120-300 is the only one of them that I'm having this problem (or any problem for that matter) with.
My Sigma 120-300mm F2.8 DG OS HSM Sports, Canon 1.4x III and 1D Mark IV
The second "replacement" lens came about after my original lens spontaneously stopped focusing at the start of a Jets game. It was quite a sight to see me running out of the stadium back to my car in one of the far flung parking lots to retrieve my Canon 300 2.8 from the trunk of my car. I missed the first half of the first quarter, but luckily nothing important happened. I sent my lens in to Sigma USA and at that point they just sent me a replacement, which I was happy enough to accept.
Unfortunately the replacement was not going to work out for me. After trying to calibrate it through the Optimization Pro software it turned out that for my 1D Mark IV body (the one camera I really NEED the lens to work on), the widest focus adjusting parameters in both the camera and lens were not enough to achieve good consistent focus across the full range (I needed more than +20 and -20 in the lens settings). So I inquired about the status of my original lens. I was told it needed to be sent to Japan for repair, which would take at least a month. That was fine since they allowed me to hold onto the replacement, despite the fact the focus was not great on the Mark IV (it was fine on my 7D, but as mentioned before that camera requires a completely different set of focus adjustment parameters).
After two weeks I heard back that Sigma Japan was claiming "impact damage" on my original lens which was not covered under warranty (I don't remember dropping or severely banging it, but OK). After all that had happened up to this point I was resigned to just keeping the replacement and letting the whole thing go. Much to my surprise my contact at Sigma USA told me he cleared the lens to be repaired under warranty (see what I mean about service?). It took almost another month, but I finally got word to send the replacement back, and then my original lens would be returned to me repaired at no charge.
So now the word "saga" basically means I have gone full circle, several times, and am pretty much back where the whole thing started. To no surprise, my repaired original lens still has the issue of front focusing in between 200mm and 300mm on the 1D Mark III and Mark IV, even though every setting in the Optimization Pro software is dead on.
For those who have asked, for calibration I have used pretty much EVERY lens calibration system and method I could find up to this point. The list includes Reikan FoCal, Agisoft, Datacolor SpyderLENSCAL and the Michael Tapes LensAlign. My favorite is the LensAlign with the added long lens ruler. I have also been asked to make a post on how to do my calibration method, which I hope to eventually get to. Right now I'm pretty much "calibrated out".
A STRANGE TWIST IN THE TALE:
I mentioned in my "Initial Rant" post that the Sigma 120-300 f2.8 Sports lens works fantastically with the Canon 1.4x model III converter. This still holds very true. You get a 160-420mm f4, with amazing quality, for a fraction of the cost of the Canon 200-400 f4 (or even the Nikon for that matter). I did discover a strange and pleasant surprise when I decided to confirm my lens calibration with the Canon converter attached. To my amazement, there is NO front focus issue on the 1D cameras when the lens is set in between 200mm and 300mm (280mm to 420mm with the converter). What could this mean? Is the camera "happier" communicating with a piece of Canon equipment in between it and the lens? I don't have a copy of the Sigma APO 1.4x converter to test and see if the same thing happens, but either way this at least makes me smile.
The Devils Marek Zidlicky, 1D Mk IV + Canon 1.4x III - 308mm @ f4 6400 ISO
100% Crop from above (the vertical banding effect is from the plastic visor)
So at this point my Canon 1.4x model III is pretty much permanently attached to the lens unless I am in need of the extra stop in low light situations. I am very happy with the quality at f4 and 420mm, and even happier at f4.5 where the loss in quality is almost nil. It is not a complete solution, but I will take it. I have gotten used to turning the zoom back and forth between 200mm and 300mm when the converter isn't attached (skipping the in-between bits), which is working well enough so far. The front focus issue is bad, but I do sometimes get in-focus action shots in between 200mm and 300mm (a function of focus inconsistency found in any lens when tracking motion).
So that's pretty much the story as it stands right now. I am using the lens almost daily, and hardly pull out the Canon 300mm f2.8 IS any more (though it is not for sale so don't ask, I still need a backup). I'm getting used to the little quirks, and will continue with the CrazyGlue on the crews if I have to. In all, I am very satisfied with the lens, and especially the service from Sigma. If and when I get around to doing a post on lens calibration I will provide a link to it here.
Lastly, I have gotten questions on how the 120-300 2.8 Sports lens works on Canon's newer cameras. I don't own any bodies newer than the 5D Mark II and 1D Mark IV. I briefly tried the lens on a 1Dx, but didn't really have enough time to come to a real conclusion on whether it shares the focus issue or not (none of my colleagues are willing to part with one long enough for me to really test it). I can only guess that the 1Dx's ability to adjust the AFMA values independently on the long and short ends of the zoom range can only help. I have not been able to try it on a 6D or 5D Mark III yet. All I can say in answer to the question is that I really can't say. At some point it would be great to be able to test the lens on these cameras.