When I set out writing this I tried to do a typical review with as many details as I could muster, but after reading it back I found it to be just so much noise. Since you can get the full specs from the Tamron web site I thought it would be more helpful to focus on why I think this is the best ultra-wide out there for Nikon DX bodies.
At $500, this 2nd gen model (B023) is priced within the range of similar offerings from Sigma and Tokina. However, this new Tamron is currently the only lens in this class to offer optical image stabilization (VC), an electro-magnetic diaphragm system, and support for Tamron's TAP-IN Console.
As for the VC, one might argue that having image stabilization isn't all that important on a lens with such a wide focal length. It isn't. But it is nice to have in slow shutter speed situations and if you shoot video hand held, it is almost a necessity. This, coupled with the electro-magnetic aperture, makes this a fine lens for video (more on that later).
Tamron's TAP-IN Console is similar to Sigma's USB Dock. It provides software for both Mac and Windows, along with a USB interface to facilitate firmware upgrades, focus fine tuning, and selecting one of three VC modes. While it doesn't appear I have an immediate need for the console with my copy of this lens, having had a copy of the original Sigma 10-20 whose firmware did not play well with my newest Nikon body, its availability was a factor in my purchasing decision.
The lens is reasonably compact for such a wide angle, and the AF and VC switches are well located, with a very positive 'click'. The zoom ring is pretty well damped, with slightly more resistance at 20-24mm. The objective end is fully retracted at 15mm, extending just shy of a quarter-inch when zoomed to either 10 or 24.
This is my first lens equipped with an electromechanical aperture. While Canon has had this for quite some time, it is a relatively recent addition to Nikon so make sure your camera body supports it (most bodies introduced since the D300 do). The biggest advantage here (other than supposedly a more responsive and accurate aperture setting) is saying goodbye to Nikon's frustrating inability with most bodies to allow you to change exposure via the aperture setting when in Live View. Yes, you can now preview exposure using all settings in Live View, even when shooting video! There is a one disadvantage though, and that is you can clearly hear the stepper motor when the aperture changes, and that will be picked up by the camera's internal mic when shooting video. Go with shutter priority, auto ISO, or manual to avoid it.
Autofocus is carried out via Tamron's new HLD (High/Low torque-modulated Drive) AF system. Tamron claims HLD enables stable and precise focusing, even with the large focusing elements used in this lens. The focus ring allows for full time manual override, and is smooth enough for one finger operation, but with enough friction to avoid being accidentally nudged. Ring rotation from minimum to maximum focus is 180 degrees. Due to the full time manual override, the focus ring does not have hard stops, but there is enough increase in friction when you reach either end of the focus range to easily feel it.
Given the 180 degree focus range, worst case scenario for auto focus speed (9.4 inches to infinity) was measured at 0.624 seconds. Other less drastic distance changes measured are:
Infinity to 1 meter: 0.28 seconds
1 meter to 32 meters: 0.127 seconds
32 meters to Infinity: 0.083 seconds
The autofocus motor is reasonably quiet, but like any lens I have used to date, it is clearly picked up by the camera's internal mic when shooting video.
The apparent build quality of this lens is surprisingly good… especially at this price point. There are seals at the mount and front element, as well as the focusing and zoom rings. The front element has a fluorine coating that repels water and oil. And while I have read conflicting reports as to whether the barrel is metal or plastic, it 'feels' like anodized aluminum to me. Sorry I won't perform a scratch test to prove that assessment, I can only tell you that when out in the cold, the barrel sections feel noticeably colder to the touch than the areas that are clearly plastic (front inner barrel/hood bayonet, switch plate, and focus scale window).
Even the front and rear caps are an order of magnitude better than what I have come to expect from third party lenses (so no need to replace them with Nikon caps), and the lens hood and bayonet mount are decidedly more substantial than I am used to with even my Nikon lenses (I noticed this immediately upon removing it from the box).
I have been shooting Nikon since 2005, and have owned a number of lenses from both Nikon and Sigma. This new Tamron has a fit and finish that is better than any Sigma I have seen, and it is as good or better than any modern day Nikons I have owned.
I am not DXOMark. While I did have the opportunity to compare it to the Nikon 10-24 and the Tokina 11-20, I didn't bother. Hell, some of the best picts on my walls were taken with that old Sigma 10-20, on a 6MP body no less. The Tamron is noticeably better.
Is it better than the Tokina? Possibly… I know of at least one very staunch supporter of the 11-16 that has said so. Shots I have seen with the Tokina show it is susceptible to some odd flaring whereas the Tamron is remarkably immune. Plus I find Tokina's focus clutch implementation to be clumsy at best (I had a Sigma macro with this same kind of arrangement and hated it).
I do have to say that one advantage to having the Nikon (albeit it at almost twice the price) would be their built-in distortion correction. However, if you use Lightroom or Photoshop I am reasonably certain you will see a lens profile for the new Tamron added soon.
The picts I have shot with this so far have been beautiful, and I find that I use less sharpening on them during development. Even the in-camera jpegs are remarkably sharp.
I think Tamron has a winner here. So much so that I will be looking hard at their other 'Gen 2' models in the future. I simply can't imagine anyone picking up this lens and not being impressed with the feel, fit and finish… and the features and handling are second to none.
With that said this is my first Tamron, so I have no track record of their reliability or longevity compared to Nikon, which excels in this regard… but it seems pretty clear Tamron is confident. They offer a 6 year warranty with 3 business day turnaround on service. That's pretty impressive. So is the ability for me to update the firmware should it ever be needed down the road, and my experience with third party lenses tells me it could.
So while I have mentioned the pros above, in the 2-3 weeks I have had this I am struggling to come up with some cons. The only one so far is that it is not a Nikon lens… and I have had compatibility issues with older third party lenses on newer Nikon bodies, so there is risk here. For me, the availability of the TAP-IN console has me feeling better about that. It is technology I would like to see Nikon adopt.