Some say that's objectives are very good, this is not true, it is downright excellent! Regardless of its riquiqui price.
Excellent dive dice f / 2.8 at all focal lengths the same 17mm (to say, rivals to 50mm with the Pentax 50mm f / 1.7 dice f / 2.8!), Almost no loss at the edges and also at all focal lengths and dice Full Opening exceptionally uniform for a zoom. I do not think you can find trans-standard much more efficient in terms of optical quality any brand (DA * included!). And it's also among the least expensive! ;)
However, it suffered (as any lens in its class néamoins) quite pronounced distortion in wide angle very (no more than "competition" was what I could see), RAS in the rest of the range. The building, although robust and quality, is less than a classy Sigma or especially a Pentax DA *, but what we ask is mainly to take pictures, rather than having a look "pro" I think. No internal motor for autofocus but Pentax k10 and k20 AF is extremely swift, at least as much as his competitor stamped "SDM"; noisier however naturally.
In short I think probably one of the best cross-Standard (APS-C) of the market in terms of optical quality, and also one of the cheapest (for a steady opening) it is great !!
