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Not really better because it is heavier!Originally Posted by Steve Axford
Sony have the advantage in that they're designing a lens for their own system, and it's well known that they use the camera's internal software to enhance the optical performance of their lenses .. ie. things like distortion and vignetting tweaks that can't be unedited out of the image if you use mainstream software. Olympus and Panasonic do the same thing.
Sigma don't have this luxury! The need to make their lenses vignette less so by actually designing that ability into the lens, no favours from Nikon and Canon on that front for them ... so invariably the lens will have to be much larger. Larger = heavier!
Same with distortion. Sony have the luxury to compromise on raw distortion performance, use the in camera software to process that distortion out and concentrate on designing the lens smaller and maintain a high level of IQ at the corners.
The 16-35/2.8 comparison is a more pertinent indicator on the topic of lens backfocus distance .. as we do have direct like for like comparisons to work with.
And looking at the equivalent Canon lens's physical specifications, there's nothing in it .. even weight is not worthy of a mention as a difference.
That 80 gram difference is almost certainly due to the Sony's unique focusing mechanism(they have an interesting linear electronic contraption that does away with large heavy ultrasonic ring motors).
What is surprising about the 12-24(more so than the 16-35) Sony lenses is the price. That's a very good price on a new lens design with those optical specs. It's very close to the Sigma, and Sigma have three brands of cameras to market it towards(ie. higher potential volumes!)
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