When I bought a 24-120mm I compared it in the 24-70mm range to the 24-70mm f/2.8 lens. The 24-120mm was very soft and so I returned the lens to B&H for a full credit.
I had a similar experience, except my 24-120 isn't really 'soft'. It's just not as good as the 24-70. To the point I would just as soon crop to gain the 70-120 compositions and have the advantage of F2.8 and better sharpness overall.
If I wanted something with an extended range I would be trying out the Sigma 24-105mm f/4 lens instead.
I read something pretty surprising recently. Lensrentals did some testing of the Sigma (includes comparisons to the 24-120, as well as the Canon 24-105).
I generally let you know what my expectations are before I start, to hopefully let you know where my personal opinion affects things. The fact that I'm just posting tests of the Sigma 24-105mm f/4 DG OS HSM Art months after the lens was released tells you a lot. I'm not excited about testing...
www.lensrentals.com
Some interesting points - the Nikon and Sigma are actually very close to each other wide open, which is a good result for the 24-120. The Sigma is best on the wide end, average on the long end.
What is fascinating to me is what Lensrentals found when they stopped the Sigma down to F5.6:
"Stopping Down
NOTE: Some comments suggest that this data is just TOO good. I will repeat all of these as soon as I can get to it, hopefully within a day – this is a new test for us and not as automated as most of the others. Until then, please take them with a grain of salt. This is rather amazing and I should have repeated it multiple times before publishing. So until this note comes down, take this as ‘might be this good’.
All lenses are sharper stopped down a stop or more. But the Sigma 24-105 sharpens up spectacularly at f/5.6. The truth is, after seeing this difference, I’d probably just plan on using this as an f/5.6 lens whenever I could. This is a much better improvement than the
Canon 24-105 IS II makes stopped down to f/5.6. (I don’t have data on the Nikon at f5.6, so I can’t comment on that – but I can’t remember any zoom improving this dramatically when stopped down just one stop.)"
and a bit further down:
"I value tradition, so I’m going to make my summary ‘This is the Best Damned 24-105mm f5.6 Lens Ever Made’. Because did you see how amazingly good this thing is stopped down to f5.6? That is a remarkable thing for any zoom lens, and even more remarkable for a zoom that ranges from wide-angle to telephoto. Honestly, if you are shooting at f/5.6 I can’t imagine any lens at any price doing significantly better than this."
Note to readers who don't follow links. There is more information in the linked article, including graphed data that shows things pretty clearly.
blog.kasson.com
