I own the Tamron 17-50mm f/2.8 lens. If you follow this blog, you will know that I had to send it in for service a little while back. I had issues with focusing, and some parts coming loose. While I had the lens in for service, I had to rent the Nikon 17-55 f/2.8 when I had a wedding to shoot. This is a bit of a comparison after using both. Not scientific at all.
First of all, I bought the Tamron because it was $450. The Nikon is $1230. A bit of a difference. I now know what that money gets you. The Nikon is a lot heavier. That could be a plus or a minus depending on what you like. The weight is because the lens has more metal in it. The lens I rented was very much a rental. It was banged up pretty good, but still worked. With the Tamron I am always very careful, and one of the issues I had was that the front ring where the hood snaps on was loose. You could wiggle it.
Sharpness is good across both lenses. The Tamron appears to be fine now that I have it back. I was never really happy with, and it seemed to get worse until I sent it in. Now I have no issues. I have not tried to examine sharpness across all apertures, and I don’t have comparison pictures, but I am happy with it now. I shoot a lot with this lens at 2.8, and it seems just fine. (My Nikon 70-200 f/2.8 feels sharper, but I haven’t¬† tried to collect proof.)
Focus speed is a world of difference. Night and day. You can’t hear the Nikon, and can’t tell when it is focusing (except for the odd time that it hunts, but so do all lenses). The Nikon seems instantanious. The Tamron is slow. I don’t really care about the noise. It doesn’t bug me. But it means that I can tell how long it takes for the lens to focus. It almost always turns to get close and then a few smaller micro adjustments. I have very bad luck with moving kids. That can be an issue with any lens, but I fell it is an issue with the Tamron.
So, it really depends how you want to use this lens. If you want a fast zoom lens (aperture) to use on a small light weight body, and price is a concern (when is it not), then this is a good option. If you want to shoot sports and moving kids, I am a little unsure on giving it the thumbs up. I do shoot my own kids with this lens, but not with great results. I try to shoot with my 70-200 if I am after moving things, but that is a much longer focal length, and a much heavier lens.
For me, I am considering replacing this with the Nikon version. This issue really holding me back right now is the full frame one. If I am going to move to a full frame camera, and I want to eventually, then the 17-55 will not work on those cameras. I will keep my D90 as a backup, so maybe it is a good lens to keep with the camera. In the meantime, I will have a better lens. Doing it over, I would probably try to save for the Nikon. Paying double (or more) seems like a Nikon Tax, but there really are good reasons that it should be priced more. It’s just whether you think the durability, the weight, and the focus speed are deal breaker issues for you.