Sigma autofocus issues

[Tomasko]

So, not long ago I bought my first Sigma lens: Sigma 50mm f/1.4 ART.
At first I thought it's working fine and I credited occasional AF misses to my incompetence. Human error is quite common when it comes to fast lenses. But then I read on the internet about inconsistent AF with Sigma lenses and it got me thinking. I set up my tripod and did some test shots. I found out it's front focusing on close distances, evens out at about 1.5m and then starts to back focus.

I experimented with AF microadjustment in my Canon 6D and these are my approx. values needed for various distances:
40cm: +17
60cm: +14
100cm: +4
150cm: 0
400cm: -10

As the offset isn't constant, I need to adjust the lens based on various distances. I thought of few options:

1. RMA (though I heard it's not 100% and can come back with different issues)
2. Sigma USB Dock (is it effective enough to justify the purchase??)
3. sell the lens and buy one from a different manufacturer (Canon/Tamron?)

Can you advise me what would you do based on these findings? Are the values too off to be fixed easily? I'm not really comfortable with sending my camera away just to get one lens fixed, so I'm not sure about the first option.

Also focusing in live view is without any issues and the lens is REALLY sharp when it nails the focus. Of course, every other lens is working perfectly fine.

 

[Destin]

I have a sigma 17-50 that presents with the same exact issues. Focuses great in live view though, which I find odd.

My game plan is to sell it and replace it with a 24-70, I’ve tried to correct the issue with AF fine tune to no avail.

 

[Tomasko]

Live view focusing works differently, that's why it's fine. LV is often use to determine if the lens is ok or not. This is why mirrorless don't have such problems with FF/BF. Unfortunately focusing through the viewfinder is a different story :/

Did you try to use the sigma dock or did you perform the correction only in the body?

 

[benhasajeep]

I'm on the fence with Sigma. I have had several for Nikon and Canon mounts. Currently have 1 Sigma lens at the moment. It had to go back for a repair. My other Nikon Sigma also had to go back for repair. But my Canon Sigma's were just fine. My issues were with the physical focusing system themselves (internal ring broke free), and one lens had very bad lens creep almost out of the box.

You may have gotten a "Friday" lens!

 

[Destin]

Live view focusing works differently, that's why it's fine. LV is often use to determine if the lens is ok or not. This is why mirrorless don't have such problems with FF/BF. Unfortunately focusing through the viewfinder is a different story :/

Did you try to use the sigma dock or did you perform the correction only in the body?

My lens is too old too use the dock, so just in camera.

I had the Tamron dock for my old 150-600 G2 and found it to be extremely useful.

 

[kap55]

I have the dock and use it on a couple of Sigma lenses (although not your 50mm). It is perfectly suited to handle the situation you are faced with. Even if you're not happy with the lens after the dock adjustments you can sell the two items together.