Well...I had three Sigma f2.8 zoom lenses that were bought new and all three had to go back fro calibrating for quite severe back focus. The 70-200 f2.8 I bought from them was nearly an inch out of focus at 4m @ 200mm. It'sP1ss poor QA...nothing else. In my entire back catalog of Canon lenses I've only ever had one that required calibration, a 17-40L that I bought S/H. Every other L lens has been pretty much perfect or at least properly QA'd in the factory. As I've said in other threads....I'm done with Sigma. They have always been a promising brand but unfortunately they never seem to deliver on their promises....certainly not compared to Canon L glass, which are in a different league as far as I'm concerned.
Sigma glass is cheap for a reason...so are their low resale values...which also speaks volumes of their market place reliability. No other lens marque needs a lens dock calibrator except Sigma...and on one else would have the cheek to charge for it either. It should have been done in the factory...if they have time to box and bag it up, they have time to run it though a calibration machine...commercial ones take seconds.
If all three lenses were demonstrating focus inaccuracies in the same direction, maybe the problem wasn't with the lenses...
They can't match a lens to a camera that isn't there when they check the lens.
Quoting Roger Cicala from his classic blog entry
"This lens is soft" and other myths:
"
Addendum: I recently saw the greatest real life example of this ever, in an online forum where the poster states ’Canon’s New XX camera sucks’ (I’m eliminating names so the bots don’t pick this up and repeat it.) He goes on to say he had a body for several years, and a
hand picked collection of lenses that he knew were perfect because he’d gone through several copies of each to get the sharpest one. Now he bought a new body and all his lenses sucked, and he’d now exchanged bodies twice and they still all sucked. So here is the perfect example of a person starting with a camera at the edge of tolerance, choosing through multiple selection a set of edge-of-tolerance lenses, and now generalizing that all the new bodies suck. The sad part is the new body has microfocus adjustment and he never even tried it. Just sent copy after copy back to the store."
If cinema lenses costing five to six figures need to be adjusted by a technician to match the cinema camera to which it is attached, a process that usually takes a couple of hours, minimum, then why would you think lenses costing less than one-tenth that would come from the factory already matched to every existing camera in a particular mount?
My anecdotal personal experiences with Canon "L" lenses:
For my copy of the EF 70-200mm f/2.8 L IS II that I bought in 2010 I currently use AFMA values of -1 (at 70mm) and -6 (at 200mm) when mated to my EOS 7D Mark II. +1 (70mm) to -4 (200mm) with 5D Mark III.
Before a drop and trip to CPS (after it was dropped the lens was demonstrating fairly strong tilt), I used AFMA corrections of +7 (at 70mm) and +10 (at 200mm) with the same 7D Mark II. I used values of +5 (70mm) and +8 (200mm) when mated to a 5D Mark III. Between the time it was dropped and the time it was repaired, I used +9 (70mm) to +12 (200mm) with the 7D Mark II. The lens performs as well after the repair as it did when new.
Before the drop that required the trip to CPS, I used -4 with a 50D, -2 with a 7D, and +1 with a 5D Mark II. Those cameras only allow a single adjustment per lens. I haven't recalibrated it with any of those after the repair because I no longer use that lens on any of those cameras.
EF 135mm f/2L: 0 with 5D Mark III, 0 with 7D Mark II
EF 17-40mm f/4L: -7 with 5D II, -1 (17mm) and -1 (40mm) with 5D Mark III,
EF 24-105mm f/4L IS: 7 (24mm) and 6 (105mm) with 5D Mark III, 0 with 5D Mark II
EF 24-70mm f/2.8L: -2 (24mm) and -2 (70mm) with 5D Mark III, -2 with 5D Mark II
Non "L" lenses:
EF 50mm f/1.4: -7 with 5D Mark II, -2 with 5D Mark III at longer distances, +1 at shorter distances.
EF 85mmf/1.8: 0 with 5D Mark III
EF 100mm f/2: +7 at medium to longer distances, +3 at shorter distances.