Dear sifu-sifu, I suspect my tokina 11-16mm DXII is having back focus issue at F2.8.
I have tried other lens, no back focus issue. I don't think is DSLR body problem.

Is this lens is having some focusing issue at big aperture by nature?
What can I do (some verification test) to further confirm this issue?

Am I able to send for calibration or repair? Any recommended repair shop?

This post has been edited by Holyjolly: Jan 4 2017, 10:46 AM

Send back to service Centre
I think no one can be repair

Hihi, sorry to hear of your problem, I totally understand how frustrating back/front focusing can be
You can verify your suspicions by following the steps here: https://photographylife.com/how-to-quickly-...utofocus-issues
Basically you just need to print out the focus chart, paste it on a wall and set up your DSLR on a tripod (must be parallel to the wall). Since you are testing a wide angle lens you need to get up close to get a shallow depth of field. Then let your DSLR autofocus and take a shot, followed by checking on a computer to see whether its really suffering from back/front focusing. To check whether the focusing issue is caused by the lens, just repeat with another lens (need to change distance depending on the lens used) and try again. If you notice front/backfocusing issues in both tests, then perhaps its a problem with the DSLR body.

*Note that it is worthwhile to do this test if you think your DSLR suffers from back/front focusing problems. I used to think my DSLR/lens had problems with focusing until I've checked and realized it was actually a problem with my shooting style

Are you using a Nikon D90 (based on your signature)? I don't think you can digitally calibrate the front/back focusing on this model. This means that if there really is a focusing problem with the body, it is probably best to send it back to the service center. (There are DIY ways to fix this problem but it is rather risky and not recommended).

On the other hand, if the focusing problem is caused by the lens, then I think it will be difficult to fix: I don't think service centers are willing to put in effort to troubleshoot and fix the problem

Yeah, I am a D90 user. I was aware that my DSLR doesn't have the auto fine tune features. Thanks for the help man.

I will carry out the test to further verify the root cause. Most likely is the lens issue. I hope got people recommend some contacts that are providing lens/ camera calibration services.