Hi, looking for some advice. Does anyone use the Sigma 17-70 or Tamron 17-50 on their A6000 with the LAEA2 adaptor? Do they dwarf the camera or do they balance OK and is the IQ good? I've got the Zeiss 16-70 but I'm not blown away by the IQ and wondering if the above might be decent alternatives
I have Sony DT 16-50/2.8 SSM, which is an awesome lens: Quiet, Fast AF and Sharp with very nice blur characteristics, and color rendition. Good close up ability (1:4 magnification). Superbly built too. The lens itself is weather resistant and has no zoom creep (an issue I find with many zooms).
It is great on either camera (a55, where it primarily serves as my kit lens, or NEX-6). Distortion at wider FL is noticeable, but I expect that in 16-20mm range especially from a zoom, and easily corrected with one click in LR. I had paid $600 for it three years ago, but I think its retail price is up around $800.
That being said, it is a relatively heavy lens at about 580g, and is quite thick (72mm filter size). It isn't overly long (IIRC, about 85mm or so at its widest FL). This means, some of that length is absorbed by the SLR mount. When the mount difference is "filled in" with adapter, you're looking at about 106-110mm length.
You can use it just as well on an E-mount body, however, if that is going to be your normal zoom lens, then you might be better off getting an A-mount body. This is why Sony E 16-70/4 OSS ZA is more appealing on E-mount body to me (Sony A-mount has its own version, although a Vario-Sonnar instead of Vario-Tessar: Sony DT 16-80/3.5-4.5 ZA).
With the 16-70/4, you actually get a better range (probably the best range for a normal zoom), cut the weight in about half without compromising build quality, significantly thinner (55mm filter size) and probably cut the effective length by a third.
A lot is made about the 16-70/4 being "only" f/4 and not f/2.8, but I don't see a point to it especially if low light photography is important (I would suggest carrying an f/2 or faster lens to compliment f/2.8 zoom anyway, which I do and so would with f/4). In fact, 70mm f/4 is a better combo for portraiture than 50/2.8, and at 16mm, f/2.8 matters little where one is more likely to use smaller apertures.