Why buy Canon when third party are this good?

[LetTheRightLensIn]

http://www.The-Digital-Picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=786&Camera=453&Sample=0&FLI=0&API=0&LensComp=101&CameraComp=0&FLIComp=0&APIComp=0

For me this comparison shows that the Tamron 24-70mm does not even come close to the MK I not even speaking about the MKII if it can deliver what the MTFs show ...

We'll see. It did better on the LensRentals tests and on a test some european magazine carried out.
For whatever reason, my results often don't match TDP and he seems to often have Tamron stuff test out poorly, for whatever reason.

[RuneL]

I've never tried a Tamron lens but I've had sigma and my overall impression is bad. AF-motors froze, AF is slow and extremely noisy, no constant manual focus, poorly built and they do not last and they freak out in moist conditions. The only Canon lens I've had break was a 50 1.8. I have a working 16-35 2.8 from 2001  and a working 70-200 2.8 from 1996-ish, they do tend to last, at least the old ones did, the newer I'm not so sure, the overall build quality seems more flimsy and they have too much plastic on them. 

[dswatson83]

The main reason I want this lens is for f/2.8 with stabilization. I WISH Canon had something like this. Either I loose the 2.8 or I loose the IS with a Canon product. If Tamron can do this with the IQ of the Canon 24-70 f/2.8 at a price that is $300 cheaper, it is tough to say no. I'm looking for a lens that stays on my camera 80% of the time. My 70-200 f/2.8 IS II is the best lens I own but it is really heavy, large, and too long for indoors. But I love shooting at 2.8 and the IS is great to have for stills and just about mandatory for handheld video. I'm sure most of us wouldn't even be talking about this lens if Canon offered one. Even if it was $2000

[Marsu42]

I'm sure most of us wouldn't even be talking about this lens if Canon offered one. Even if it was $2000

Well, maybe *most* of us - but given the choice, with my budget I'd still get a 35L + Tamron 24-70is for the price of ob one Canon 24-70ii ...

[dilbert]

I'm sure most of us wouldn't even be talking about this lens if Canon offered one. Even if it was $2000

Well, maybe *most* of us - but given the choice, with my budget I'd still get a 35L + Tamron 24-70is for the price of ob one Canon 24-70ii ...

Yup!

Tamron are packing a lot of value into their lenses, more so than Canon.