Recently purchased a few Tamron lenses for my d7200 - 24-70mm G2, 70-200mm G2, and 100-400mm. All Tap-in compatible (thank goodness, as you'll see).
Initially I was a bit disappointed when I field tested these at certain focal lengths. It seemed I was producing really sharp images at certain distances and focal lengths, and not at others, and could tell the lens was not focusing properly in same cases. First thought perhaps it was VC acting up, so tested them tripod mounted – Same results. I read some reviews of the recent lens offerings and noticed other people complain about focus calibration issues, so I decided to calibrate them.
The 24-70mm G2 was a bit all over the place in regards to back-focused in certain cases and front-focused in others. Spent a day working on it (granted it was my first time using the Tap-in), but I eventually got it dialed in. Took it outside and a quick field test proved it was super sharp now, and consistent across the range!
The 100-400mm was pretty easy and pretty good out-of-the-box, but I noticed a slight tendency to front-focus as it zoomed. Within 1 hour I had the lens set absolutely perfect at 4.9 feet and 11 feet (the two Tap-in configuration distances). I also noticed that the lens hit perfect focus consistently.
The 70-200mm G2 was a whole ‘nother issue. It was horribly back-focused at 135mm, and I mean REALLY bad at 5 meters (“mid” distance adjustment point in the Tap-in); visually I could see that it was a good foot back-focused at 5 meters! – I had to use the body’s AF fine tune to go -5, and went -20 (+-20 is max in the Tap-in config), which made me have to go back and redo all the other config points I had done up to that point after making the adjustment in body fine tune. At 70mm, 100mm, and 200mm though, it was FRONT(!) focusing (but not super bad). Basically, though I don’t have the numbers in front of me, the 70mm, 100mm, and 200mm lengths are now set to around +10 to +15, while the 135mm focal length is set to -20. I also noted that at this 135mm and especially out past 10 feet, the AF hunts much more than the other focal lengths AND many times it still hits front- or back-focus pretty bad (several inches either way); but I feel that I’ve found and calibrated what the “average” is for that focal length.
So I saved the configuration on the 70-200mm G2, and reset the lens back to “factory” – did a field test and sure as can be, as I move from 100 to 200mm, this lens loses focus performance big time until I get back toward 200mm, at which time it comes back again. So I plugged the lens back in to the Tap-in and applied the configuration I had saved, and then repeated the field test. SOOO much better – but again I am noting that the 135mm-150mm focal range seems to be “difficult” for this lens.
I’m looking for any thoughts or opinions in my experience here – is this normal for the 70-200mm (as I have not seen anyone complain specifically about what I found), and do I potentially have bad glass in this one?