10-18-2013, 09:48 AM
Those "half a dozen" 24-70-s don't have optical stabilization and the other half you mentioned are not really pro or even semi-pro lenses. Or did I miss something ? But anyway, you know what you would like to compare, 300 is a bit more way off compared to 105mm than Tamron's 70mm in the other direction. So that wasn't a good example either 
If I would look for a stabilized f/4 semi pro grade standard zoom, optical stabilization, weather sealing, very good IQ, I'd consider the Tamron as well since that's kind of a unique construction and by meaning f/4 I'm not limiting myself to f/4 glasses, but the usage of f/4 where the Tamron for example excels already. 70 -> 105, hmm, some may miss it, some not. For me it's not a drastic loss and this is still a standard zoom category of course. Even at Nikon, 120mm is already kind of a "why?" because from my point of view, Canon's 24-105 is just perfect with the 105 end.
I'm not meaning exact focal length in such a comparison, but rather category in pro grade stabilized FX standard zooms and there aren't much out there yet. -_-
If I would look for a stabilized f/4 semi pro grade standard zoom, optical stabilization, weather sealing, very good IQ, I'd consider the Tamron as well since that's kind of a unique construction and by meaning f/4 I'm not limiting myself to f/4 glasses, but the usage of f/4 where the Tamron for example excels already. 70 -> 105, hmm, some may miss it, some not. For me it's not a drastic loss and this is still a standard zoom category of course. Even at Nikon, 120mm is already kind of a "why?" because from my point of view, Canon's 24-105 is just perfect with the 105 end.
I'm not meaning exact focal length in such a comparison, but rather category in pro grade stabilized FX standard zooms and there aren't much out there yet. -_-