[A64]

Sigma 24-105mm f4: 88.6mm x 109.4mm, 885g, 82mm filter

Canon 24-105mm f4: 83.5mm x 107mm, 670g, 77mm filter

Nikon 24-120mm f4: 84mm x 103mm, 670g, 77mm filter

Tamron 24-70 @ f4: 88.2mm x 108.5mm, 825g, 82mm filter -> and we need some MTF's. So simple. And yepp, it's stabilized as well. 

[JJ_SO]

If you don't realize it lacks between 50% and 70% focal length (35 or 50mm) and if you think a wide open not useful lens is okay to compare, just because it has sort of similar weight and filter size - well, why not.  :unsure:

 

But don't forget half a dozen other 24-70/24-85, oh, and why not take a 28-300 into comparison?

[A64]

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. -_-  

[JJ_SO]

If you compare lenses with such a difference in focal length it's just not what I call comparison, and I put the 28-300 only in to exaggerate towards the other direction. For a lot of people 70mm is just not enough - and for those who are happy with it there are already more options than only that Tamron you find so interesting.

 

So, why exclude those from a comparison? And by the way: Hey, why don't YOU do the comparison and tell us what you found? I mean, it's always easier to tell others what they should work on instead of doing it myself.