I tried mode 3 briefly, but it didn't seem to matter much. I know Tamron claims the 4.5 stops of stabilization is for mode 3, but I read a review somewhere that said mode 1 was actually better. Unfortunately, the viewfinder is pretty shaky in mode 3. I think the review said that could've been the reason why they didn't get as many keepers. Hopefully, some of the professional review sites write about this lens soon. I'm surprised there aren't more out yet.
Mode 3 is definitely the way to go for two reasons. First off, it's better (my G2 gets about a 50% hit rate with a D500 at 1/40th of a second for me, vs 1/100th with my G1, and 1/200th with my old Siggy 150-500). Secondly, the shakiness of the viewfinder allows you to directly see how steady your technique is. My #1 issue with my G1's VC was that you had no idea if you were steady or not because the viewfinder image was rock solid (the G2's mode 1 does the same). The steadier you are, the more effective VC/VR will be.
I'll still use mode 1 most of the time because the steady view makes putting the AF point on target much easier, but when I want the maximum stability (from the VC and myself), mode 3 is the way to go. Most of the things I shoot (critters, birds, planes) don't hold still, so such slow shutter speeds aren't a good idea anyway. I'm also curious to try mode 2 out on fast-moving airplanes, hopefully the VC will stabilize along the full motion and not just shut off stabilization along the panning direction.
Sorry to hear about your issues with your lens's VC. Mine works great. I honestly did not expect to get that kind of improvement over the G1.
Another thing I like about Mode 3 is that there is no "settle" time. All of my other Tammy VC lenses require a half second or more of VC-on time (half-press the shutter) to fully stabilize, otherwise you degrade your image. Haven't tested the G2's Mode 1, but the mode 3 simply doesn't stabilize until the shutter opens, so it should be immune from this typical Tamron VC issue.
Good to hear your comments on the IQ (that it's largely a wash). I'll take the greater range with similar IQ over 1/3rd of a stop at the long end any day
(plus the faster F stop at the wide end kind of makes up for it IMO). I also like that as Tamron refines their firmware and VC logic, I can download their updates, a big improvement from the G1, and finally matches the Sigma lenses in that regard.
I've been reviewing my images of my G1 at 600mm and F/6.3. One thing I'm seeing in the new lens vs those images were the lack of "haze" or fuzziness that I saw on the G1 (and the similarly-designed Sigma 150-500 it replaced). One of my shots of a hummingbird at 1600th of a second actually looked as sharp at F/6.3 as my typical shots are at F/9 on the G1.
This is all based on only a few dozen test shots I've taken. Hopefully I'll get a chance soon to do a more thorough shoot so I can really tell if it's noticeably better than the G1, but I do like the lack of haze/fuzziness at close distance shooting wide open at 600mm.
