I just received a new Tokina 11-16mm f2.8 yesterday. It's a Nikon mount and I use it on the GH3 + G6 with either a Metabones Speed Booster or the Novoflex Nikon -> MFT adapter. Should be both high quality precise adapters so flange distance shouldn't be the problem here I assume.

Today I took the Tokina for a test on the GH3 with the Novoflex adapter. It focusses just barely to infinity. Might be 1mm over it, but not more. It's either just on infinity or can't quite reach it. It's a matter of nanometers. My Sigma 18-35mm on the other hand focusses pretty far over infinity and is tack sharp at all apertures.

The Tokina however seems sharp to me, but the left side is clearly softer than the right or middle. This is more pronounced at 16mm than it is at 11mm and of course a bit more pronounced at 2.8 vs smaller apertures, but it is there in every shot. The Speed Booster gives me the same issues and might be even a bit worse.

How do I focus? I'm on manual focus, tap the screen to magnify 10x and focus until it is sharp. This is also how I concluded that it is barely going to / over infinity when I magnify a point in the far distance.

I have a couple of examples here which show the problem. Look how the trees / stones are softer on the left than on the right. The problem starts at about 1/3rd of the image.

http://i79.photobucket.com/albums/j138/timboz/P1090149.jpg http://i79.photobucket.com/albums/j138/timboz/P1090159.jpg http://i79.photobucket.com/albums/j138/timboz/P1090156.jpg

Click on the zoom function to be able to see it clearly.

What should I do? Send it back to the shop and exchange for a new one? Or is this 'acceptable' with these kind of super wides? Will infinity focus adjustment also take care of this decentering problem? Christian Schmeer has made a great tutorial about how to do it on the Tokina. Could that help? Or don't bother?

http://www.christianschmeer.com/blog/Tokina-11-16mm-f-2.8-Infinity-Focus-Adjustment

Thanks!!