motobloat: I'm surprised no one has mentioned this here:
This is a *street photographer's* dream lens.
You get 28mm, 35mm, and 50mm equivalents, and everything in between, all at f/1.8. No more do you have to just pick one of the three classic 'street' lenses - you can have them all.
New street kit? Small SLR like D3200 or 100D + this lens - small, fast, light, high-resolution, and really, really flexible.
Maybe because I regularly workout, but carrying a 1.79 lb/ 810 g lens should really not be an issue at all. I would weep if that is considered to be heavy. I carry around an older 70-200mm f2.8 lens that weighs a little over 3 pounds with no issue and this is without a tripod or image stabilization and get great photos.
viking79: Nice, finally equivalent lenses for APS-C. I have been waiting ages for the sub f/2 fixed aperture zooms for APS-C. For ages they kept trying to sell people on full frame f/2.8 lenses, what a waste of weight on APS-C. This I can do, unfortunately the zoom range is a bit limited, but if the price is right I am all over it.
It will be available for A-mount, just like the 35mm 1.4 from Sigma, it just won't be in the initial offering/at launch which is what is shown above. So I wouldn't worry about it not being available for A-mount, because it should be at some point in the near future (a few months) after the launch.
topstuff: Awesome idea.
I fear it will be as soft as a kitten wide open though. I hope I'm wrong.
Sigma new lens lineup has been sharp wide open and setting industry standard for quality with what is released in their Global Vision Lens Lineup. It is exciting to see the Global Vision lens lineup expand, a few months ago I was stating that they needing to expand this more quickly, and it seems they are doing just that.
When the new Sigma lenses (more expensive than their previous lenses) are a few hundred dollars cheaper than the Canon and Nikon equivalents and decimate them in performance, more people are going to start to realize that they are the way to go for now. I am interested to see how Canon, Nikon, and Sony will respond to the new Global Vision from Sigma.
veroman: I don't know of a single Sigma lens at f/2.8 or larger that's sharp wide open. Is there one? If history is any indication, I suspect this new zoom won't really come into its own until f/2.8 ... which really doesn't make it all that competitive to Tamron's 17-50 f/2.8. I'd like to be wrong, 'cause the idea is terrific. I'd purchase it in a second if f/1.8 is sharp. Would let me shoot all day long at ISO 400 or lower with my small Canon.
Sigma's newer primes have been some of the best lenses in the industry. Starting with the 85mm 1.4 which received many accolades for it's performance at 1.4. The new Sigma Global lens series primes have been setting the bar in the industry for wide open performance, like the 35mm 1.4. Now granted these lenses are primes, so we will see how good they do with the wide angle zoom with a constant 1.8 aperature, but if their recent lens releases are any indication, it will be basically the best available at launch in its category.
OvinceZ: I would love to have this version to take photos of flowers. Should be superb.
My understanding is that the new SD1(M) and the DPM series produce superb reds. I have a SD14 and I know that reds can very tricky from time to time when they bleed. I am sure there would be a forum post that at least discusses the reds from the new series somewhere on dpreview.