All,
My Tamron 70-200 was delivered last night. I didn't have a whole lot of time to play with it, but I did do a few low-light shots and the results were... interesting.
Here's a few observations:
1.) AF
Two things jumped right out at me about the AF. The first thing is that it's LOUD. Loud enough that I had to put the lens away at 10pm because I was annoying my fiancee who was working on the computer on the other side of the room. Her exact words were "I hope you never photograph a wedding with that thing because they'll kick you out"
The second was tha it does hunt in VERY low light (like 1/2s, f2.8 ISO1600 territory). The lens has a heck of a time focussing at that low lighting.
With that said though, in better light (1/60s, f2.8, ISO1600) it focuses with no real problems. It's pretty fast, finds contrast well (although it won't focus on a flat white wall at 200mm under that lighting) and doesn't back/front focus at all.
2.) IQ
The lens is really sharp across the frame. Maybe just a little bit (and I mean very little) soft in the corners at f2.8 but not noticable in a real life picture. The DOF is pleasing and colors are really good.
3.) MF
I hate the MF on this lens. Here's the deal. It's got that 'feature' where you pull the focus ring back to engage MF, buuuuuut on the K10D you also have to switch the camera body to MF also or you just end up turning the screw drive in the camera when you spin the focus ring... very bad. The good news for me is that I almost never use MF, so it's a rather moot point.
4.) Build
This thing is a big lens. Especially with the hood on it, it can be very ominous looking. It's pretty high quality though and lighter than it looks. It doesn't balance incredibly well on my K10D w/ BG, the weight is a little front of where I like to hold it but I'm sure I'll get used to that.
Now for pictures:
Like I said I didn't take many and a few came out blurry because it was dark and I was hand holding at <1/60s for a lot of shots.
Here's a 'good' f2.8 shot, ISO400 and a crop of it. Natural lighting for this shot (a lamp in the room).
and a crop of that shot. Sharpened and leveled in PS.
I'll update this after I have a chance to really try out the lens this weekend and put my thoughts in the lens review database.