Thanks to this thread, I chanced upon the Tamron 17-35 f2.8-4 [LD] IF (fair price) in a local store, and got this instead of spending the money on 17-40L or the Tokina 17-35. The tokina is quite a big lens compared to the 17-40L, being larger in diameter you'll probably have to spend quite a bit to get 82mm filters (if you are using them).
The Tamron's not quite the build quality of both constant aperture lens from Canon and Tokina. If you've used the Tamron 28-75, it'll resembled similar build quality. Note that the lens extends a bit when zooming out to 35mm, when zoom out, will be roughly the same height as the Canon 17-40 L.
I really don't think I have any use for the f2.8 on such a wide angle. So those figures of vignetting and soft wide open in the corners doesn't really bother me. But it's a little brighter to look through the VF at 17mm for sure.
Just so that you are aware of the largest aperture for the respective and well-used focal lengths
17 - 20mm - f2.8
24 - 28mm - f3.5
35mm - f4
Without sharpening, the corners are indeed not resolving a lot of details. There's probably a slight difference in ability to resolve details in the L versus the Tamron, but I don't quite pixel peep. As long as the overall feel of the image has got the details it needs to bring the visual experience you intended to, good enough for me.
As for distortion, you'll notice it for sure. There's quite a bit of barrel distortion, so you may be worried if you are into architecture. I was prepared to accept that until I saw my Lr4 having the Tamron lens profile! 1 click and all of that's minimized. Excellent!
Sounds like I easily pleased? Hahaha ... So all in all, it's really a budget FF Wide angle Lens, which in my opinion after several hours of playing with the images it produced on the 5D, I would say value for the money you pay it for.
Pros
- Sharp in the center [Landscape apertures]
- Relatively small in size (dimensions)
- Relatively light, and I don't mind body heavier than lens
- 77mm filter thread so I can use all my filter adapters, filters, CPL etc that I already had
- Seems a little (just a tiny weeny little bit) wider on this lens than the 17-40 L (i may hallucinating)
Cons
- Quite a bit of Vignetting that's still evident in small apertures (can be corrected)
- Quite a bit of Barrel Distortion (can be corrected in LR 4)
- Plasticky feel (I don't really care at this price)
Here's a test subject (again) from my study window and I did some usual PP (includes sharpening, resizing) -
And here's 1 review way back in time ... click
here.