[vinzer]

I don't understand the market of this lens. I can't even tell if its a entry level lens.

OK you get a zoom that starts out at 4.5 in the other end. Don't people buy that kind of lens only care about superzooms? Unless its a cheap kit lens to low ball the entry body+lens combo, in which case why add IS?

Who are the target audiance of this lens?

The target market is most likely Canon and Nikon entry-level users. It probably doesn't cost Sigma much to swap out mounts and do limited runs for Alpha- and K-mount users just in case.

[glanglois]

The glass is not half full, it's twice as big as it needs to be.

a true engineer!

FWIW, I love these forums - where the technologist and the artist come together. The result is (sometimes) "creative conflict". I learn a great deal.

[AndrewG NY]

I think the spec makes some sense. It is fairly "Sigma-like" to spec a lens just slightly faster-than-common; this might be attractive to those who might be shopping it against a f/3.5-5.6 but don't want something as bulky as a f/2.8 zoom--or even the 17-70 with its 72mm filter size. My understanding is that Sigma's existing "kit"-level zoom isn't among the more popular offerings so this might help them out. I say 'bravo' to Sigma for giving people choices.

This is the first time I've seen anyone attempt to allow lens-based and body-based stabilization to co-exist. It will be interesting learn more about implementation details...are you supposed to turn off body SR? Seems somewhat likely that Sigma decided it was more cost-effective and possibly distinctive (stabilized in the VF) to find a use for OS in their more limited Sony/Pentax-mount production runs than to remove it.

[vinzer]

I think the spec makes some sense. It is fairly "Sigma-like" to spec a lens just slightly faster-than-common; this might be attractive to those who might be shopping it against a f/3.5-5.6 but don't want something as bulky as a f/2.8 zoom--or even the 17-70 with its 72mm filter size. My understanding is that Sigma's existing "kit"-level zoom isn't among the more popular offerings so this might help them out. I say 'bravo' to Sigma for giving people choices.

This is the first time I've seen anyone attempt to allow lens-based and body-based stabilization to co-exist. It will be interesting learn more about implementation details...are you supposed to turn off body SR? Seems somewhat likely that Sigma decided it was more cost-effective and possibly distinctive (stabilized in the VF) to find a use for OS in their more limited Sony/Pentax-mount production runs than to remove it.

Well, if you want to consider it as co-existence, Panasonic's OIS lenses have been mounted to in-body stabilized Olympus DSLRs before, though if I recall correctly, those two don't work in harmony, so one of the two stabilization systems have to be turned off.

It remains to be seen how Sigma's OS lenses will work with Sony's and Pentax's stabilization systems.