Hi ....(this will be little lengthy)...I have posted here before regarding the Sigma 50mm and the 35mm Art Lenses.
I own both and with some hesitation and quite a bit of attention to getting the lenses to perform consistently well.
I bought the 35mm Art first and I did not really test it at first...I was amazed by the sharpness. I am more an artistic photographer than I am a measurebator. ... I also bought the 50mm Art (when I could finally get my hands on one), and I was well aware of the focusing issues when I purchased that lens. I also bought a the Sigma Lens Dock when I bought the 50mm.
Here is how I test...I shoot specific images just for the testing and I will shoot a specific spot close and a specific spot much farther away. I repeat this a few times and look at my results. I use center focus points and edge points. I use a "Show Focus Points" Plug-in in LR so that I know exactly where I focused. (I will mention that both my "Show Focus Points" Plug-in and Canon's DPP show the focus point location on my computer screen slightly to the right of where I actually focused using the camera (5DIII). This is consist with every shot. There is a half to about 3/4 of a focus point shift from my camera to the two softwares I use on the computer? (Does anyone else experience this?)
Anyway...My 1st 50mm Art was all over the place and I could not get it to focus consistently. After wasting hours of my life ...I returned the lens to B&H, explained the situation (which they were well aware of) and they gladly sent me another lens. The 2nd lens was MUCH more consistent....and needed just a slight bit of tweaking on the Sigma Lens Dock (I did not touch the focus adjustment in the camera). I have used the lens quite a bit and it is consistently accurate wide open...Any issues I have are to do with operator error...I think that this lens is just fantastic. (but I worry about it shifting because of all I have read.)
OK...the 35mm ...Needed a LOT of adjustment on the Dock +13 in all 4 zones. At least it was consistently of and I could have used the AFMA in the camera to straighten this out as well. I must say I am a little disturbed and how big this adjustment is. It leaves me uneasy. ...but the lens seems to perform consistently well now that I have taken the time to adjust it.
Now ...I do not sit around with charts and..blah..blah blah... I use the lenses to go out and shoot images. ...and when I am shooting wide open I check my focus point occassionally and the lenses seem very accurate....and i just love the IQ...Especially for what I paid.
Its a drag to have to do all of this work...but in my case I feel that it was worth it. Both these lenses are capable of creating really great and unique images!!!
So...those of us who have trouble with consistent AF and lousy AF off the center point just need to do more voodoo, be less demanding, and more understanding?
I'm not sure you've carefully read many of the posts.
I'm happy you were satisfied with your second copy of the 50.
I'm hoping to hear great reports if Sigma fixes erratic AF with a firmware update.
I read all the posts. I had a different experience. I had a lousy lens. I sent it back. I was able to get a better copy.
Not doing any vodoo.
My photos look fantastic and are in focus where I want them to be. Just reporting my point of view, how I set up my camera and lenses, my experience and the results with MY equipment. I am a very technical guy. ...but I like to go out and shoot. The results are more than satisfactory...but that's me. Obviously other people have had different experiences. I have read many reports where photographers are having good experiences with both of these lenses, too.
I just love these lenses. They were just a bit of extra work to set up in my case.