There is a new version of the Tokina 11-16mm f/2.8 AT-X - it's "II" suffix will tell you.
There are 2 differences between the original Tokina 11-16mm f/2.8 AT-X and the newer lens. The newer "II" version has internal focus motor and newer multilayer coating on the front element.
The Tokina 11-16mm f/2.8 AT-X II will work on older DSLRs which dont have a motor in the body - D5000 old D40 etc, i.e. those bodies that cannot drive an AF screw type lens without a motor in it. the new 11-16mm dx II lens is like the newer AF-S and AF-I nikkor lenses, whereas the original version was more like the older AF lenses which required the body to have a focus motor present.
A lot of things depend on your camera body. Having said that, if you only have a DX body and no other, then you only need to look as far as Nikon's own DX series lenses.
The only exception would be the Tokina 11-16mm, and maybe the Sigma 150-500mm (or 50-500mm) which are actually OK lenses, but anyone will tell you, money spent on lenses is not money wasted. Money spent on digital camera bodies is ALWAYS money wasted. Money spent on 3rd party lenses is almost always wasted, however the Tokina 11-16mm is proving to be worthy if you look at 2nd hand prices often.
IMO you should Ignore Tamron and all other (incl tokina & sigma) lenses other than mentioned above, you simply will not get the desired sharpness or image quality. I've played with many different DX & FX lenses on my D7000 and find the genuine DX nikkor lenses work the best - and in many cases better than the FX ones too.
If you have a film body and a DX or an FX and DX body, then the nikon nikkor 14-24mm f/2.8 AF-S is the one to get and it costs huge $, even second hand. It also cannot take any filters at all… not even gels, which the 14mm f/2.8D ED (nikons current widest AF prime lens) can take. So if you want to use filters, and have both FX and DX format bodies, the 14mm is the widest lens you can use on both bodies. You cant use wide DX lenses on film or FX bodies at the wide ends, as they do not fill the whole frame / sensor.
Nikon have an excellent 10-24mm DX lens, which is newer than the 12-24 and the tokina 11-16mm. You can buy them online reasonably priced. try DWI and the usual online culprits like cameras direct etc for pricing.
I don't know what other lenses you have covering specific focal lengths, but if you are adding an ultrawide specifically to cover the sub 35mm space, then the 10-24mm is the one to get. It's the newest, it's light and small compared to the 12-24 DX and much smaller and lighter than the 14-24mm FX lens
It's also faster than the 12-24mm, lighter, and even though it's a pumper zoom and not IF, it's still awesomely WIDE. It's about double the price you can get a brand new tokina 11-16mm, and the reason is because it covers almost twice the range.
The 12-24 is pretty darn good and would be the lens I'd buy if I didn't already have the tokina 11-16 (I wanted WIDE, and I got it), and only because I have a tendency to drop lenses from time to time, and the 10-24 was not available back then, and the tokina lens is also built like a brick outhouse- reviews were unanimously spectacular from many photographers around the globe. My D7000 also drives it without any issue. They have improved the coating on the front element, (not that I have a problem with ghosts or flaring anyway) and added a motor so older dslr bodies can drive the af now.
I found that I really have to mess around with the tokina in photoshop to get the corrected image, where as nikkor lenses seem very easy by comparison…
I shoot the 11-16mm on my D7000 in RAW+JPEG and fine resolution for the jpeg. WB is A2 and picture control set to VIVID with sharpening +4 and Saturation +2 for nature/urban
and for portraiture / animals I set Standard with sharpening to +6 and Saturation +2.
I'm not taking thousands of images per day. I'm a hobbyist and I like to take my time. If you're more pro than I am, then you'll know what you want to do.
You may find other settings you prefer, I'm just providing mine as an example. Hope that helps.
EDIT: 15/07 - I sold the 11-16 and purchased the 12-24DX AF-S G ED lens, and it's every bit as good as the Tokina, and the 1mm difference is all but negligible and it's SHARP in the corners wide open!
Nikon D7000 | 12-24G | 35mm 1.8G | 55-300 4.5-5.6 EG VR | FishEye 10.5mm 2.8G ED
Nikon F4E | 50mm 1.4D | 135mm 2.8 DC | 24-120mm 3.5-5.6D |
Nikon FTn | 18mm 4 | 28mm 3.5 | 180mm 2.8 | 200mm 4 | 300mm 4 | 80-200mm 4.5 |